Search Results (1,197)

Elemental sulfur frequently coexists with organic polysulfides in environmental samples and laboratory sulfurization experiments, complicating the accurate analysis of sulfur speciation. Reliable methods for selective sulfur removal are therefore required to avoid analytical artifacts. In this study, we systematically evaluated commonly used chemical sulfur removal approaches, including treatment with metallic copper and silver and reaction with tetrabutylammonium sulfite, and compared them with a chromatographic separation method based on C18 reversed-phase silica gel column chromatography. Model organic polysulfides, dimethyl polysulfides, diallyl polysulfides, dibenzyl disulfide, and cyclic polysulfide lenthionine were used to assess method performance under controlled conditions. The results demonstrate that chemical treatments are non-selective and lead to substantial decomposition of organic polysulfides, particularly for longer-chain compounds. In contrast, C18 reversed-phase silica gel column chromatography enables efficient and selective removal of elemental sulfur while preserving the original composition of organic polysulfides, with recoveries in the range of ~90–107%. These findings indicate that commonly applied sulfur removal procedures may introduce significant biases in sulfur speciation analyses. The chromatographic approach presented here provides a reproducible and non-destructive alternative for sample preparation, improving the reliability of studying sulfur speciation and transformation in natural and laboratory systems. Full article

Neutron-capture products, such as molybdenum (Mo) isotopes, are an important tool that cosmochemists use to constrain the stellar precursors of the Solar System and, potentially, the origin of life on Earth. Using high-precision Mo isotope data from meteorites and terrestrial samples, studies have attempted to reconstruct Earth’s formation by linking its composition to material sourced from various heliocentric distances. Debate, however, persists about the nature of Earth’s late-stage building blocks that accreted around the time the Moon formed and whether they delivered life-essential elements (i.e., carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur; CHNOPS), which are presumed to be more prevalent in the outer Solar System. Initially, it was proposed that the Moon-forming event involved the addition of material from both the inner and outer Solar System, thereby providing a mechanism for the delivery of a significant portion of life-bearing elements late in Earth’s formation. Recent advancements in analytical chemistry and their application to a wider range of samples than previously studied, however, led to a revised constraint: the Moon-forming event was dominated by inner Solar System material that was less enriched in CHNOPS, thereby relaxing the requirement for the delivery of a consequential amount of life-bearing elements late in Earth’s formation. A review of analytical approaches and findings is presented here to highlight the utility of neutron-capture products in constraining the origin of life on Earth. Full article

The Idrija mercury deposit represents one of the largest mercury formations globally, ranking second only to the Almadén deposit in Spain. The deposit has been exploited for more than five centuries and represents one of the most historically significant and extensively studied mercury mines worldwide. The Karoli orebody is characterized by a high abundance of pyrite (50 to 90 vol.% of the rock) and exceptionally rich cinnabar mineralization, with contents reaching up to 78 wt.% Hg locally. This study investigates the trace-element composition of Py3 pyrite from the Karoli orebody using LA-ICP-MS analysis to examine variations within Py3 pyrite, revealing insights into ore-forming processes and mineralization characteristics. Trace-element analysis of pyrite was performed and complemented by microscopic examination of thin sections. Three different pyrite types were identified: fine-grained framboidal Py1, subhedral to euhedral Py2, and larger, well-developed euhedral Py3. LA-ICP-MS analysis of Py3 pyrite grain revealed low trace-element contents, with maximum values remaining below 100 ppm. These observations, combined with published sulfur and mercury isotope data, suggest that Py3 pyrite crystallized under stable growth conditions from mercury-rich, low-salinity hydrothermal fluids. Our research provides insights into Py3 pyrite formation and the characteristics of the hydrothermal fluids in the Karoli orebody, serving as a solid foundation for further studies. Future research is envisioned to include the analysis of Py2 grains to complement the current dataset, with further investigations of fluid composition, salinity, and fluid inclusions. Full article

The uranium metallogenic potential of the Dadongshan–Guidong granite belt in northern Guangdong, especially the Jiangwan area in the eastern Dadongshan pluton, remains unclear, which hinders the evaluation of exploration prospects in this area. In this study, we present new data on the mineralogy, U-Pb geochronology, trace element, and sulfur isotopic compositions of pitchblende and associated pyrite from the Jiangwan uranium deposit (JUD). The uranium ore is dominated by pitchblende, which commonly occurs as crustiform and fine veinlet-like aggregates. Part of the euhedral-to-subhedral pyrite grains are enclosed or partially replaced by pitchblende. LA-ICP-MS analyses of pitchblende yielded a Tera–Wasserburg lower intercept age of 60.2 ± 0.5 Ma (MSWD = 2.6, n = 16), indicating that uranium mineralization occurred during the Paleocene. Additionally, the pitchblende has ΣREE contents of 2489–4960 ppm and high U/Th ratios (>1000), indicating that the pitchblende has a hydrothermal origin, forming under moderate- to low-temperature conditions (T< 350 °C). HREE-enriched patterns suggest that carbonate complexing played an important role in uranium transport. Weak positive Ce anomalies in pitchblende, together with pervasive hematitization, indicate relatively oxidizing conditions for the ore-forming fluid. Pyrite has Co/Ni ratios of 1.03–4.53, indicating a hydrothermal origin. The δ³⁴S values of pyrite, varying from −4.23‰ to −1.21‰, suggest that the sulfur source was unlikely to be derived solely from the granitic host rocks, but may have been influenced by mafic dike-related sulfur and hydrothermal fluid–rock interaction. Combined petrographic and geochemical evidence suggests that pyrite formed before pitchblende and likely acted as an important reductant during uranium precipitation. These results indicate that the JUD records a Paleocene hydrothermal uranium mineralization event, which corresponds to the age of the identified main mineralization period in the Xiazhuang ore field. Full article

Whether the genesis of gold deposits in the Northeastern Jiaolai Basin is consistent with that in the Northwestern Jiaodong area remains controversial. This study presents in situ Rb-Sr dating of sericite, along with in situ trace element and sulfur isotope analyses of pyrite in the Longkou gold deposit. The sericite Rb-Sr inverse isochron yields an age of 120.9 ± 2.4 Ma, indicating that gold mineralization occurred in the Early Cretaceous. Two generations of pyrite, Py1 and Py2, were identified. Py1 is anhedral and hosted in relatively low-grade, weakly altered marble wall rock. Py2 is euhedral to subhedral and hosted in relatively high-grade, strongly altered marble ore. The δ³⁴S value of Py1 is 7.38‰, whereas that of Py2 is 6.79‰. The decrease in δ³⁴S values from Py1 to Py2 reflects an increase in the oxygen fugacity of the ore-forming system. These features suggest that fluid–rock interaction led to an increase in oxygen fugacity, thereby triggering gold precipitation. The mineralization age and precipitation mechanism of the Longkou gold deposit are consistent with those of the Northwestern Jiaodong area. The Longkou gold deposit is best classified as a Jiaodong-type gold deposit. Full article

The Duolong porphyry copper–gold district, located in the northwestern segment of the Bangongco–Nujiang metallogenic belt on the southern margin of the South Qiangtang terrane (Tibet), hosts typical porphyry-style Cu-Au mineralization with well-defined alteration zoning from potassic through chlorite–sericite to propylitic assemblages. Based on integrated in situ major/trace element and sulfur isotope analyses of pyrite and chalcopyrite from different alteration zones, we identify two discrete episodes of magmatic-hydrothermal activity that exerted distinct controls on metal endowment. Sulfur isotope signatures define a systematic evolution from the earliest, high-temperature potassic stage (δ³⁴S: Py-I −3.70 to −1.16‰, mean −2.14‰; Cp-I −4.92 to −0.90‰, mean −2.54‰) through propylitic alteration (Py-II: 1.20‰–5.16‰, mean 3.06‰) to the later chlorite–sericite stage (Py-III: −2.00 to 1.86‰, mean 0.06‰; Cp-II: −2.50 to 0.58‰, mean −0.77‰), tracking progressive fluid cooling and changing fluid sources. Trace element systematics further discriminate these episodes: sulfides from potassic and chlorite–sericite zones are enriched in trace elements, whereas propylitic pyrite is depleted, with potassic pyrite recording the highest Cu concentrations (559–7256 ppm, mean 2302 ppm) and chlorite–sericite pyrite containing the lowest Au contents (0.01–0.59 ppm, mean 0.10 ppm). Gold mineralization occurs as native gold exsolved from chalcopyrite, and the markedly low Au concentrations in chlorite–sericite pyrite (0.01–0.59 ppm, mean 0.10 ppm) demonstrate that gold exsolution was largely completed during the first, high-temperature magmatic-hydrothermal stage. Collectively, these results establish a detailed geochemical framework linking sulfide composition to specific hydrothermal stages, providing new constraints on the processes of porphyry copper–gold mineralization in a collisional setting. Full article

Four algal adsorbents were prepared from two types of green sea algae (Ulva lactuca and Ulva pertusa), either by treatment with concentrated sulfuric acid or without treatment. A comparative study of Au(III) adsorption in an HCl medium was performed. While both untreated adsorbents showed good performance at low HCl concentrations, the treated adsorbents achieved quantitative adsorption and high selectivity for Au(III) across a broad range of HCl concentrations. The adsorption of Au(III) onto the algal biomass adsorbents followed the typical Langmuir monolayer adsorption model. At an HCl concentration of 0.010 M, the maximum adsorption capacities were 1.14, 0.86, 6.57, and 6.28 mol kg⁻¹ for DUL, DUP, TUL, and TUP, respectively. A kinetic study conducted at different temperatures was consistent with the pseudo-first-order kinetic model and enabled estimation of the activation energy of the adsorption reaction. Structural changes before and after treatment were analyzed using FT-IR spectroscopy. Confirmation of Au(III) adsorption and its subsequent reduction to the elemental state was achieved through XRD and SEM/EDX analyses as well as digital imaging of the Au-loaded adsorbents. Finally, the adsorbed and reduced Au was successfully desorbed using an acidic thiourea solution. Full article

Sulfur–soybean oil polymers with tunable thermal insulation properties were synthesized via inverse vulcanization of elemental sulfur and soybean oil and reinforced with biochar (BC) derived from spent barley biomass. Biopolymer films (F-BPs) with sulfur contents ranging from 20 to 80 wt% were prepared, and biochar-filled biocomposites (F-BP-Cs) were obtained using different filler loadings and processing routes. Their structural, morphological, thermal, mechanical, and surface properties were systematically analyzed to establish structure–property relationships, with particular focus on thermal transport behavior. Differential scanning calorimetry (DSC) revealed that sulfur contents ≤ 50 wt% favored the chemical incorporation of elemental sulfur into the polymer network via covalent bonding, significantly reducing the presence of free crystalline sulfur in the material. SEM images and porosity analysis revealed that BC incorporation and processing conditions significantly affected microstructural connectivity and air-filled porosity. As a result, F-BP-C materials exhibited low thermal conductivities, reaching values of ~0.033–0.039 W/(m·K), comparable to commercial insulating materials such as cork and polymeric foams. This reduction was attributed to increased structural disorder, high interfacial density, and enhanced phonon scattering within the heterogeneous polymer–BC–air system. These findings demonstrate the potential of these biocomposites as sustainable thermal insulating materials derived from industrial and agricultural waste. Full article

This work presents an energy-efficient and simple method for producing luminescent, antibacterial sulfur quantum dots (SQDs). For the first time, polyethyleneimine (PEI)-coated SQDs were synthesized via a mechanochemical technique, utilizing either elemental sulfur or sodium thiosulfate as the sulfur source. The roles of hydrogen peroxide (H₂O₂) as an etching agent and of sodium hydroxide (NaOH) in the PEI-mediated SQD formation were investigated. The as-synthesized SQDs were characterized by UV-visible, Raman, infrared (IR), and photoluminescence (PL) spectroscopy, as well as by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Both TEM and AFM analyses revealed similarly small SQD sizes (average diameter ~3 nm), independent of the sulfur source used. The influence of synthesis conditions on the optical properties, including the photoluminescence quantum yield (QY), was evaluated. SQDs derived from elemental sulfur, PEI, and NaOH exhibited the best water solubility and the strongest photoemission in the 400–550 nm range. Antibacterial activity was assessed against representative Gram-positive and Gram-negative strains, and minimum inhibitory concentration (MIC) values were determined. The PEI-coated SQDs demonstrated antibacterial activity against the Gram-positive bacteria Bacillus subtilis, Staphylococcus aureus, and Staphylococcus epidermidis, which is attributed primarily to the sulfur component. Full article

The production of green hydrogen via aqueous electrolysis of hydrogen sulfide (H₂S) holds significant potential to address challenges related to sustainable energy generation and environmental protection. The electrocatalytic splitting of water polluted with highly toxic H₂S is attractive for industrial applications because the process: (i) is less power-consuming than direct thermal H₂S decomposition; (ii) achieves high Faradaic efficiencies for hydrogen production; and (iii) yields elemental sulfur as an added-value by-product. This review covers a brief discussion on sulfide-containing water sources and electrochemical methods for hydrogen production from H₂S, specifically Direct, Indirect, and Electrochemical Membrane Reactor (EMR) systems. To become commercially and economically attractive, these approaches require improvements in electrolysis efficiency through the development of low-cost electrode materials that are resistant to sulfur poisoning and corrosion, while possessing high catalytic activity, enhanced stability, and durability. Early research focused on carbon-based materials combined with noble metal oxides, transition metal compounds, and related materials. Since their practical performance is limited, investigations have shifted toward nanostructured electrocatalysts with unique crystal structures and designs, which show significantly improved efficiency for H₂S electrolysis. This review highlights the potential of H₂S electrolysis for hydrogen production, giving special attention to recent advancements in electrode materials. Full article

Sandstone-hosted uranium deposits in the western Qaidam Basin are spatially associated with hydrocarbon-bearing structures, yet the specific roles of different sulfur sources in uranium mineralization remain poorly constrained. This study aims to distinguish the contributions of bacterial sulfate reduction and hydrocarbon-associated sulfate reduction to uranium precipitation by integrating detailed petrography, in situ trace element analyses, and sulfur isotope measurements of chalcopyrite from the Yuejin II deposit. Chalcopyrite is restricted to high-grade uranium ores and occurs intergrown with uranium minerals, pyrite, baryte, and carbonate cements. Trace element patterns indicate that oxidizing brines acted as the main transport medium for both uranium and copper, as evidenced by positive correlations between U and brine-related elements (Ba, Sr, Na, K). Positive U-Th correlations with relatively constant Th/U ratios (0.027–0.225) reflect a combination of source composition, fluid transport capacity, and limited thorium remobilization in this near-source, hydrocarbon-rich environment. Correlations between U and high field strength elements (Sn, W) point to a highly evolved granitic origin, with Altyn granitoids likely supplying the copper. Sulfur isotopes show a clear bimodal distribution: one group exhibits heavy δ³⁴S values (+6.9‰ to +18.5‰), while the other shows extremely light values (–36.0‰ to –44.6‰). The light group reflects bacterial sulfate reduction in shallow strata, supported by framboidal pyrite textures, whereas the heavy group corresponds to surface-derived sulfate reduced at hydrocarbon-associated redox fronts, rather than direct incorporation of deep H₂S. The lack of intermediate δ³⁴S values indicates that two discrete sulfur reduction mechanisms coexisted within the same deposit, refining genetic models for uranium mineralization in petroliferous basins and challenging frameworks that invoke a single dominant sulfur source. Full article

Coal gasification slag (CGS) is rich in Si-Al-Ca components and thus has potential for ceramic utilization, but associated heavy metals may pose environmental risks. In this study, CGS from Yili (Xinjiang, China) was used as the major raw material (80 wt%), with clay and waste glass as additives, to prepare ceramsite by firing green pellets (8–12 mm) at 1000–1200 °C. The phase evolution, microstructure, and heavy-metal migration were characterized, and the leaching safety was evaluated. Increasing temperature leads to progressive quartz consumption, enrichment of feldspar-type crystalline phases, and liquid-phase sintering, which together enhance densification. The apparent density and single-particle compressive strength exhibit an “increase-then-decrease” trend with temperature and reach maxima at 1150 °C, where the compressive strength is 15.38 MPa. Heavy-metal behavior is element-specific: As and Zn show stronger volatilization, whereas Mn, Ba, Ni, and Cu are largely retained in the solid phase; Cr shows intermediate, temperature-dependent volatilization. After firing at ≥1150 °C, the leached concentrations of Cr, Mn, Ni, Cu, Zn, As, and Ba under the sulfuric acid–nitric acid test (HJ/T 299-2007) are below the Class III limits of the Chinese Groundwater Quality Standard (GB/T 14848-2017). Considering phase/structure evolution, mechanical performance, and short-term heavy-metal leaching, 1150 °C is identified as the preferred firing temperature in this work. Full article

The Dongwujiiazi deposit is a structurally controlled orogenic gold deposit situated in the eastern part of the Chifeng–Chaoyang gold belt along the northern boundary of the North China Craton. This study establishes a comprehensive metallogenic model for the Dongwujiiazi gold deposit by integrating whole-rock geochemistry (major and trace elements), in situ trace elements and REEs in zircon, multi-isotope systems (H, O, S, Pb), and precise zircon U–Pb geochronology. Five types of intrusive and associated rocks are identified within the main biotite-pyroxene gneiss host of the Dongwujiiazi gold deposit: mylonitized granitic pegmatite, mylonitized porphyritic monzogranite, propylitized fine-grained quartz monzodiorite, quartz monzonite, and porphyritic dolerite. The gold-bearing polymetallic sulfide ores are composed of pyrite, chalcopyrite, sphalerite, galena, digenite, and native gold. Zircon grains in the Dongwujiiazi gold ore (2502 ± 15 to 2539 ± 18 Ma) are inherited from surrounding Neoarchean gneiss, recording older crustal sources rather than forming contemporaneously with the gold mineralization. H–O isotopes indicate that the ore-forming fluids were mixed in origin, involving both magmatic and metamorphic components. S and Pb isotopes suggest that the mineralizing sulfur was mainly derived from a magmatic source, while lead originated predominantly from lower crustal materials associated with the surrounding high-grade metamorphic rocks. In this study, we present a new metallogenic model for the Dongwujiiazi gold deposit, in which slab-derived and lower-crustal metamorphic fluids interacted with ascending magmas, resulting in fluid mixing and gold precipitation within structurally controlled zones of gneissic host rocks. Combined geochemical and isotopic evidence (H–O, S, Pb) indicates contributions from both magmatic and metamorphic sources, supporting formation as an intracontinental orogenic gold system in an active continental margin. Full article

The peripheries of rare-metal metallogenic systems frequently host skarn-type or hydrothermal vein-type Pb-Zn deposits, though their genetic connections with parental systems remain debated. The newly identified Gariatong W-Mo polymetallic metallogenic system in the Lhasa Terrane displays well-defined Nb-Ta-Rb, Mo-W, W-Mo, W-Bi, and Pb-Zn-Ag metallogenic zoning, establishing it as an exemplary site for investigating genetic relationships between Pb-Zn and rare-metal mineralization. This investigation targets skarn-type Pb-Zn deposits spatially associated with rare-metal orebodies at Gariatong, utilizing integrated analytical approaches, including in situ LA-ICP-MS trace-element analysis of sulfides, sulfur isotope geochemistry, and LA-ICP-MS elemental mapping of sphalerite, to constrain metal sources, characterize fluid evolution, and establish genetic correlations with the rare-metal system. Key findings include the following: (1) sphalerite shows enrichment in Fe, Mn, Co, and Cd, while pyrite contains elevated As, Pb, Co, Cu, and Mn. Fe, Cd, and Mn primarily occur as solid solutions or nanoparticles, whereas As and Pb exist as micro-inclusions. (2) Sphalerite Zn/Cd ratios (73.6–184) and Co-Ni-As ternary diagrams confirm a magmatic–hydrothermal skarn origin. (3) Mineralization occurred under moderate-temperature, mildly oxidized conditions, as constrained by sphalerite Fe contents and mineral assemblages. Sulfur isotope compositions (δ³⁴S = −1.0‰ to 3.2‰; mean: 1.9‰) indicate a magmatic sulfur source. This study reveals that the Nb-Ta-Rb mineralization, quartz-vein- and greisen-type W-Mo deposits, and skarn-type Pb-Zn orebodies—all genetically associated with highly fractionated granites—constitute an integrated magmatic–hydrothermal system with vertical (depth-related) zoning relative to the granitic intrusion. These results provide critical constraints for understanding rare-metal–Pb-Zn genetic associations and suggest that Pb-Zn mineralization may serve as a key exploration indicator for rare metals in the Lhasa Terrane. Full article

The Huoyanshan Cu-Zn volcanogenic massive sulfide (VMS) deposit, located in the North Qilian Orogenic Belt, China, is of significant economic importance. This study provides new constraints on the ore-forming processes through high-resolution in situ trace element and sulfur isotope analyses of pyrite and sphalerite using LA-(MC)-ICP-MS. Petrographic and geochemical investigations identified three distinct generations of pyrite (Py l to Py III). Early-stage Py I and Py II are characterized by high trace element contents (Au, As, Bi, Cu, Pb), elevated Co/Ni ratios (>1–10), and enriched δ³⁴S values (+4.98‰ to +7.47‰). These signatures indicate precipitation from high-temperature, reduced magmatic–hydrothermal fluids influenced by thermochemical sulfate reduction (TSR). Late-stage Py IIl exhibits markedly lower Co/Ni ratios (<0.1) and lighter δ³⁴S values (+3.72‰ to 3.89‰). This geochemical shift reflects a transition toward a cooler, more oxidized environment driven by the incursion and mixing of ambient seawater as the hydrothermal system waned. Trace element geochemistry of sphalerite reveals an average crystallization temperature of 265.8 °C (derived from the “GGIMFis” geothermometer), consistent with fluid inclusion data and representing a thermal “snapshot” of the waning hydrothermal stage. Systematic discriminant analysis using Ga/In, Ge/In, and Co-Ni-As systematics further confirms a strong magmatic–hydrothermal affiliation. Full article