Search

This article provides a detailed exploration of the geography, mining history, and mineralogy of the Elkhorn Mountains in southwestern Montana. It focuses on the Elkhorn and Radersburg mining districts and discusses the specific mines and minerals found in the area. The article also delves into the concept of epitaxy, which involves the growth of crystals on preexisting crystals, and explains the different types of oriented intergrowths. The authors conducted a study on the epitactic relationship between quartz and hemimorphite minerals, observing their structural similarities and suggesting a shared framework as the reason for this relationship. The article concludes with acknowledgments to mine owners and individuals who assisted in the research. [Extracted from the article]

The phase transformation and vanadium leaching mechanism of stone coal during two blank calcined stages are systematically studied. Composition, structure, and morphology of the materials are analyzed by ICP‐AES, BPMA, XRD, FTIR, and SEM. The results show that the main components of stone coal are SiO2, C, aluminosilicate and FeS2, V2O5 is 0.70%. Two‐stage roasting is a process of deformation, melting, and reconstruction of stone coal, the oxidation of pyrite, decomposition of aluminosilicate, sulfation of calcite, combustion of carbon and the formation of calcium vanadate occur in the first stage, the oxidation of low‐price vanadium occurs in the second stage. At −0.074 mm ≥90%, liquid solid ratio 1.5:1, 10% sulfuric acid reaction at room temperature for 3 h, the vanadium leaching rate in each material is in the order of roasting slag>decarbonized slag>stone coal. [ABSTRACT FROM AUTHOR]

Previous studies have indicated that acid-washed pyrite is inert toward aqueous U(VI) under most pH conditions at ambient temperature, even though insoluble UO 2 is the thermodynamically predicted product for the reduction of U(VI) by pyrite. Considering the exothermic nature of nuclear waste, the interaction between uranyl nitrate/acetate and natural pyrite was studied at temperatures ranging from 25 °C to 85 °C and at pH values between ∼4.0 and ∼9.5, to simulate the scenarios encountered in a high-level radioactive waste repository. The results revealed that the reactivity of pyrite toward aqueous U(VI) significantly increased with rising temperature, and the reaction could be described by a pseudo-first-order kinetic equation. Activation energies were calculated to be 79.4 ± 10.6 and 45.7 ± 3.8 kJ⋅mol−1 for the reduction of uranyl nitrate, and 78.2 ± 5.2 and 42.2 ± 5.8 kJ⋅mol−1 for the reduction of uranyl acetate, at pH values of ∼4.5 and ∼5.0, respectively. These values indicate that the reaction is controlled by the surface chemical processes. In addition, the complete reduction of aqueous U(VI) to UO 2 product was first observed for the reactions at pH ∼4.0 to ∼5.5 when the temperature was ≥75 °C. Conversely, non-stoichiometric UO 2+x (s) (0 < x ≤ 0.67) was found at lower temperatures within the same pH range, and also at 85 °C with a reaction pH of ∼9.5. Moreover, the ratio of reduced U(IV/V) on pyrite surfaces increased gradually over time, indicating that reaction time played a significant role in the reduction products. The findings are essential not only for the safety assessment of the high-level radioactive waste repository, but also for understanding the metallogenic mechanism of U(IV)-bearing ore deposits under the relevant anaerobic and hydrothermal conditions. [ABSTRACT FROM AUTHOR]

Te–Bi bearing minerals are commonly present in many hydrothermal gold deposits and can provide important physicochemical constraints on their mineralization. The gold mineralization in the Xiejiagou gold deposit is hosted in the Mesozoic Linglong granite and consists of auriferous quartz veins and subordinate disseminated ores in the vein-proximal alteration zone. Three types of pyrite were identified that formed in stage I, II, and III. Gold occurs mostly as native gold and electrum (Ag > 20 wt.%) inclusions in or filling microfractures in pyrite. The abundant auriferous pyrite-quartz veins contain an assemblage of tsumoite and hessite. The tsumoite occurs as irregular inclusions in the Py1 and is intergrown with the chalcopyrite. The hessite occurs as irregular inclusions or along the margins of the Py2, and it coexists with the gold and galena. The tellurium fugacity continually decreased from stage I (log fTe2 = −8.8 to −10.7) to stage III (log fTe2 = −13.8 to −17.0). The sulfur fugacity increased from stage I (log fS2 = −8.6 to −11.4) to stage II (log fS2 = −7.2 to −11.4), and then, it decreased from stage II to stage III (log fS2 = −9.8 to −13.0). These data indicate the conditions of the gold precipitation during the ore formation process. A detailed study of gold distribution in texturally different pyrite and the paragenetic association of tellurides provide valuable information on the distribution pattern of gold and in understanding the processes of gold deposition and evolution. [ABSTRACT FROM AUTHOR]

The Paleo-Mesoproterozoic North Singhbhum Mobile Belt (NSMB) is a fold-thrust belt typically found in a collisional setting and is well known for hosting gold mineralisation. A study carried out in the northern part of NSMB depicts varieties of acid volcanic rocks along with mica schist, ferruginous cherty quartzite, black shale, and sheared granite, which are all ubiquitously traversed by quartz veins/reefs. In the study area, gold mineralisation is mostly restricted to brecciated quartz reef occurring ENE–WSW along S1 foliation, which also depicts syn to late kinematic brittle–ductile shearing. The petrographic studies of mineralised cherty variant of quartzite in quartz reef depict the presence of two generations of the quartz vein. The older one is smoky/bluish, altered, recrystallised and consists of disseminated and stringers of pyrite, chalcopyrite, etc., whereas the younger veins are milky white and lack mineralisation. The presence of pyrite–pyrrhotite and chalcopyrite–pyrrhotite associations and conversion of pyrite to pyrrhotite along fracture depicts prograde metamorphism. Trace elemental mineral chemistry depicts significant Au enrichment in pyrite. A positive correlation between Co and Ni concentrations in pyrite indicates hydrothermal origin. Au–As ratio explains the enrichment of gold in pyrite, where gold occurs as a solid solution in pyrite, which is generally referred to as invisible gold. The presence of gold grains/nuggets at the microscopic level and in pan concentrate as well as considerable analytical value in bulk rock coupled with occurrence in sulphide structure, points towards the bimodal nature of gold mineralisation. Mode of occurrence, nature of mineralisation, and surficial, structural and mineralogical characteristics suggest gold mineralisation of the study area is of orogenic type. [ABSTRACT FROM AUTHOR]

Exponential increasing demands for base metals have made meaningful processing of their quite low-grade (>1%) resources. Froth flotation is the most important physicochemical pretreatment technique for processing low-grade sulfide ores. In other words, flotation separation can effectively upgrade finely liberated base metal sulfides based on their surface properties. Various sulfide surface characters can be modified by flotation surfactants (collectors, activators, depressants, pH regulators, frothers, etc.). However, these reagents are mostly toxic. Therefore, using biodegradable flotation reagents would be essential for a green transition of ore treatment plants, while flotation circuits deal with massive volumes of water and materials. Pyrite, the most abundant sulfide mineral, is frequently associated with valuable minerals as a troublesome gangue. It causes severe technical and environmental difficulties. Thus, pyrite should be removed early in the beneficiation process to minimize its problematic issues. Recently, conventional inorganic pyrite depressants (such as cyanide, lime, and sulfur-oxy compounds) have been successfully assisted or even replaced with eco-friendly and green reagents (including polysaccharide-based substances and biodegradable acids). Yet, no comprehensive review is specified on the biodegradable acid depression reagents (such as tannic, lactic, humic acids, etc.) for pyrite removal through flotation separation. This study has comprehensively reviewed the previously conducted investigations in this area and provides suggestions for future assessments and developments. This robust review has systematically explored depression performance, various adsorption mechanisms, and aspects of these reagents on pyrite surfaces. Furthermore, factors affecting their efficiency were analyzed, and gaps within each area were highlighted. [ABSTRACT FROM AUTHOR]

Invisible gold hosted by pyrite represents a large proportion of gold resources worldwide. Gold is enriched in pyrite relative to hydrothermal fluids by five orders of magnitude, but controls on the hyperenrichment of gold in pyrite remain unclear. Here, we present the first micrometer- to nanometer-scale evidence for a colloidal iron sulfide phase that forms a precursor to pyrite and shows a remarkable capacity to scavenge gold from ore fluid. In chalcedony cement of breccia ores from the world-class Daqiao epizonal orogenic gold deposit, China, we find that numerous iron sulfide colloids, together with silica colloids and amorphous carbonaceous matter, formed from a highly supersaturated ore fluid in response to rapid fluid depressurization. Mechanisms that favor gold incorporation into iron sulfide colloids include large specific surface areas, abundant structure defects, negatively charged surfaces, high reactivity, and sequestration by silica colloids. These iron sulfide colloids subsequently aggregated and transformed to spherical cryptocrystalline pyrite aggregates. This process may be common during hydrothermal gold mineralization. Co-precipitation of amorphous carbonaceous matter plausibly enhanced the stability and dispersibility of iron sulfide colloids, facilitated sequestration of iron sulfide by silica, and adsorbed minor amounts of gold. Iron sulfide colloids represent a previously unrecognized mechanism for hyperenrichment of invisible gold in pyrite under rapidly changing and potentially non-equilibrium conditions. This study emphasizes that the iron sulfide colloids may be an important component of conceptual models for hydrothermal gold mineralization within Earth's crust. [ABSTRACT FROM AUTHOR]

An enormous quantity of titanium slag has caused not merely serious environment pollution, but also a huge waste of iron and sulfur resources. Hence, recycling iron and sulfur resources from titanium slag has recently been an urgent problem. Herein, hematite nanoparticles were fabricated through a pyrite reduction approach using as-received titanium slag as the iron source and pyrite as the reducing agent in an nitrogen atmosphere. The physicochemical properties of the hematite nanoparticles were analyzed using multiple techniques such as X-ray diffraction pattern, ultraviolet–visible spectrophotometry, and scanning electron microscopy. The best synthesis conditions for hematite nanoparticles were found at 550 °C for 30 min with the mass ratio of 14:1 for titanium slag and pyrite. The results demonstrated that hematite nanoparticles with an average particle diameter of 45 nm were nearly spherical in shape. The specific surface area, pore volume, and pore size estimated according to the BET method were 19.6 m2/g, 0.117 cm3/g, and 0.89 nm, respectively. Meanwhile, the fabricated hematite nanoparticles possessed weak ferromagnetic behavior and good absorbance in the wavelength range of 200 nm-600 nm, applied as a visible light responsive catalyst. Consequently, these results show that hematite nanoparticles formed by the pyrite reduction technique have a promising application prospect for magnetic material and photocatalysis. [ABSTRACT FROM AUTHOR]

Pyrite is the most widely distributed sulfide mineral with a wide range of uses, and pyrite is mainly recovered by means of flotation in practical production, and the commonly used flotation collectors are mainly xanthates with good flotation performance. The adsorption behavior of commonly used collectors ethyl xanthate and butyl xanthate on the surface of pyrite is investigated by using the density functional tight bounding theory (DFTB). The results show that when a single reagent acts on the pyrite surface, butyl xanthate has a stronger effect than ethyl xanthate, and the adsorbed mineral surface shows obvious hydrophobicity. The interaction between ethyl xanthate and butyl xanthate had a stronger effect than that of a single reagent, and the simulation of the flotation environment at ordinary temperature using molecular dynamics revealed that the synergistic adsorption of the two different reagents on the surface of pyrite was more hydrophobic, that is, the synergistic adsorption of the combined collector of ethyl xanthate and butyl xanthate on the surface of pyrite was stronger. The results of the study are of great significance for the synergistic effect between the combined collector and the mineral. [ABSTRACT FROM AUTHOR]

Cobalt is a critical and strategic metal mainly found as associated element in several types of deposits, of which skarn‐type deposits are the major sources. Han‐Xing type skarn iron deposit, having high grade iron ore and associated cobalt, is a typical skarn‐type iron ore in China. But the complete recovery and exploitation of cobalt are restricted because of the lower grade of related cobalt and the dearth of prior research on its occurrence condition and enrichment mechanism. In this paper, pyrite from five typical ore deposits in the Han‐Xing area was studied by using electron probe microanalysis (EPMA) and laser‐ablation inductively‐coupled‐plasma mass‐spectrometry (LA–ICP–MS) techniques to decipher the occurrence state and enrichment mechanism of associated cobalt in skarn‐type iron deposits. The results show that Co2+ replaces Fe2+ in pyrite through isomorphism. The distribution of cobalt in pyrite from different deposits varies greatly, that is, in the Xishimen iron deposit, the cobalt content is comparatively enriched in the pyrite's core. In contrast, in other deposits, the cobalt content is concentrated in the pyrite's rims, where it can be up to 1000 times higher than in the core. The cobalt mineralization in Han‐Xing area can be divided into several stages. The sulphur element of sulphide is mainly derived from evaporite, while cobalt mineralization occurred in the early stage with pyrite formation or in the late stage by metasomatism/cementation of Co‐rich ore‐forming fluid. The magma assimilated with the Ordovician evaporite not only promoted iron mineralization, but also became the main controlling factor for cobalt enrichment. [ABSTRACT FROM AUTHOR]

Two accretionary sediment sequences from Sites 1245 and 1252 recovered during Ocean Drilling Program (ODP) Leg 204 at southern Hydrate Ridge were investigated to explore the response of geochemical partitioning of iron and sulfur isotopic composition of authigenic pyrite to non-steady-state depositional and diagenetic scenarios. Five iron species were characterized by a modified sequential extraction procedure that covers almost all iron-bearing minerals in sediment cores, including: (1) iron-bearing carbonates, mainly siderite; (2) ferric (hydr)oxides, probably ferrihydrite and/or lepidocrocite; (3) magnetite; (4) iron-bearing silicates; and (5) pyrite. Highly reactive iron has been accumulated for a long-term steady-state history and its pyritization, to varying degrees, is limited by availability of dissolved sulfide. This causes pyrite and siderite occurred in the same sedimentary layer and shows an inverse relationship between their concentrations. From this, their proportions to highly reactive iron can be chosen for evaluating the degree of sulfidization. A significant change in sulfur isotopic composition of pyrite (-42.4 to +16.8‰ VCDT) indicates that the steady-state conditions are dramatically limited, where the d34S values higher than -20‰ may result from an upward shift of SMT zone close to the seafloor or a sudden, massive depositional event. To explain the downcore sulfidization effects and pyrite d34S values, we developed two categories of conceptual scenarios based on variations in sedimentation rate and methane flux. The geochemical features similar to those derived from each scenario were searched in the sediment columns and the non-steady-state events behind the scenarios were proved to be consistent with the real observations. Thus, iron species and pyrite d34S values can be regarded as a proxy to differentiate different non-steady-state depositional and diagenetic controls on the sedimentary record. [ABSTRACT FROM AUTHOR]

The Perron deposit, located in the northern part of the Archean Abitibi belt, bears some of the highest gold-grade mineralization for orogenic-vein-type deposits worldwide (High-Grade Zone: HGZ). More than 13 gold-bearing zones with different sulfide assemblages, hydrothermal alterations, and gold grades have been recently outlined, and they range from volcanogenic to orogenic in origin. In addition, seven zones are hosted in a restricted volume of ~1 km3, which is called the Eastern Gold Zone. Pyrite, sphalerite, pyrrhotite, and chalcopyrite—each from a different gold-bearing zone—were analyzed with LA-ICP-MS to decipher their genetic links, mineralizing processes, and temperature of formation. The temperatures calculated with the sphalerite GGIMFis thermometer range from 348 to 398 °C. All gold-bearing zones recorded volcanogenic hydrothermal inputs at different intensities, manifested by pyrrhotite. Pyrite was late-metamorphic and related to the orogenic gold system induced by the contact metamorphism of amphibolite facies. The pyrrhotite grains had very homogeneous trace element signatures in all zones, which is a characteristic of metamorphic recrystallization, exhibiting a loss of mobile elements (Au, Te, Bi, Tl, Sn, W, In) but high concentrations of Ni, Co, and As. Conversely, the pyrite was systematically enriched with all elements depleted from pyrrhotite, bearing five specific signatures of element enrichments: W, Tl, Sn, In-Cd-Zn, and Bi-Te-Au. For gold-rich zones (e.g., the HGZ), gold was linked to the Bi-Te-Au signature of pyrite, with Bi enrichment occurring at up to 72,000 times the background level in Archean shale pyrite. It was concluded that gold was transported, at least in part, as Bi-Te melts in the previously documented non-aqueous orogenic fluids, hence accounting for the very-high-grade gold content of the HGZ. Genetically, the metamorphism of primary gold-bearing volcanogenic mineralizations was the main source of gold during the overprinting of amphibolite (600 °C) in a metamorphically induced orogenic mineralizing event. A strong volcanogenic pre-enrichment is considered the main factor accounting for the gold endowment of the Eastern Gold Zone. [ABSTRACT FROM AUTHOR]

The Baoshan deposit is one of the important Cu-Pb-Zn deposits associated with granitic rocks in the Nanling Range, South China. Here, we present He and Ar isotope data for the Baoshan deposit to decipher the contributions of mantle-derived volatiles and heat to its Cu-Pb-Zn mineralization. The ore-forming fluids in sphalerite and pyrite exhibited 3He/4He ratios up to 1.51 Ra. A linear correlation between He and Ar isotopes suggests that the ore-forming fluids were a mixture of a predominantly mantle-derived fluid with a high 3He/4He ratio and a shallow crustal fluid, characterized by a low 3He/4He ratio. The δ34S values of sulfides in the Baoshan deposit ranged from +2.30 to +5.21‰, consistent with the magma-derived sulfur. The calculated 3He/Q ratios for the ore-forming fluid exceeded those of mid-oceanic ridge hydrothermal solutions by 10 to 50 times, indicating that the ore-forming fluids acquired both heat and volatiles in a convective hydrothermal regime rather than a conductive one. Therefore, there is a significant contribution of mantle-derived volatiles, heat, and possibly metals, to the Cu-Pb-Zn mineralization in the Baoshan deposit, and the continuous influx of mantle-derived fluids/melts probably plays a crucial role during the Cu-Pb-Zn mineralization related to granitic rocks. [ABSTRACT FROM AUTHOR]

The Qinling orogen in central China contains several black shale-hosted gold deposits, but the age of their formation and a possible relation between gold mineralization and regional tectonism remain undetermined. Here we present results of in situ monazite U-Th-Pb dating and sericite Rb-Sr dating of the Xiajiadian black shale-hosted gold deposit to provide tight constraints on the time of gold deposition and information on the tectonic setting under which the deposit formed. The Xiajiadian gold deposit is mainly hosted in black shales of the Lower Cambrian Shuigoukou formation, with minor ores contained in sandy conglomerate of the Lower Devonian Xichahe formation. Gold ores in the black shales have been intensively oxidized and consist mainly of hematite, goethite, gypsum, quartz, calcite, native gold, and unrecognized iron oxides. However, gold ores in the sandy conglomerate are free of oxidation and thus provide an opportunity to date the formation of the Xiajiadian gold deposit. The ores consist of pyrite, marcasite, sericite, and quartz, which are associated with a variety of accessory minerals, including monazite, apatite, and titanite. Gold is mainly present as structure-bound ions or nanoparticles in pyrite and marcasite, but minor native gold grains also occur as inclusions in pyrite. Monazite is well developed in the ores, and has close textural association with Au-bearing pyrite and marcasite. Most monazite grains have zoned textures consisting of a core area (Mnz1) and an overgrowth zone (Mnz2). Mnz1 contains 4.8–13 wt.% ThO2 and shows large variations in HREE and prominent negative Eu anomalies in the chondrite-normalized REE patterns. It yields common lead-corrected 208Pb/232Th dates ranging from 910±10 to 416±4 Ma (2σ). These dates are interpreted in terms of a detrital origin for monazite in the core area. Mnz2 has much lower ThO2 contents of 0.8–1.7 wt.% and shows weak negative Eu anomalies in the chondrite-normalized REE patterns. It yields common lead-corrected 208Pb/232Th dates of 229–209 Ma (2σ) with a weighted mean of 217.6±3.0 Ma (2σ), which is considered as the time of Mnz2 crystallization. Sericite in gold ores and associated alteration zones has close relations to Au-bearing pyrite and marcasite, and yields a well-defined Rb-Sr isochron age of 222.2±3.3 Ma (2σ). The sericite Rb-Sr age is indistinguishable within analytical errors from the weighted mean Th-Pb age of Mnz2. The age data presented here indicate that the Xiajiadian gold deposit formed at ca. 220 Ma in the Late Triassic (Norian). We therefore suggest that gold mineralization at Xiajiadian occurred during the transitional stage from oceanic subduction to continental collision that led to the formation of the Qinling orogen. During this stage, metamorphic devolatization of the underlying Early Paleozoic to Proterozoic carbonaceous sequences likely supplied ore fluids from which the Xiajiadian gold deposit formed. [ABSTRACT FROM AUTHOR]

Denitrification is of great significance for low C/N wastewater treatment. In this study, pyrite autotrophic denitrification (PAD) was coupled with a three‐dimensional biofilm electrode reactor (BER) to enhance denitrification. The effect of current on denitrification was extensively studied. The nitrate removal of the PAD‐BER increased by 14.90% and 74.64% compared to the BER and the PAD, respectively. In addition, the electron utilization, extracellular polymeric substances secretion, and denitrification enzyme activity (NaR and NiR) were enhanced in the PAD‐BER. The microbial communities study displayed that Dokdonella, Hydrogenophaga, Nitrospira, and Terrimonas became the main genera for denitrification. Compared with the PAD and the BER, the abundance of the key denitrification genes narG, nirK, nirS, and nosZ were all boosted in the PAD‐BER. This study indicated that the enhanced autotrophic denitrifiers and denitrification genes were responsible for the improved denitrification in the PAD‐BER. Practitioner Points: PAD‐BER displayed higher nitrate removal, EPS, NAR, and NIR activity.The three types of denitrification (HD, HAD, and PAD) and their contribution percentage in the PAD‐BER were analyzed.HAD was dominant among the three denitrification processes in PAD‐BER.Microbial community composition and key denitrification genes were tested to reveal the denitrification mechanisms. [ABSTRACT FROM AUTHOR]

Tunnel waste constitutes a prevalent by‐product of highway construction in high‐altitude mountainous and hilly regions. Sulphide minerals exhibit a unique distribution pattern within the alpine hills. Consequently, tunnel excavation can disrupt the stability of these sulphide minerals, rendering the tunnel waste susceptible to generating secondary environmental hazards during stockpiling. This research delves into the migration and transformation dynamics of potential environmental pollutants in tunnel waste through geoenvironmental simulation techniques. Controlled variables were employed to simulate various conditions, including surface illumination, internal anaerobiosis, water content and aerobic environments. The study's findings indicate that the presence of pyrite in the waste stream primarily drives the secondary contamination of the tunnel waste. Pyrite within the slag tends to react and form sulphuric acid in the stockpile environment, thus creating an acidic milieu that exacerbates the release of existing contaminants. The emergence of an anaerobic environment and a photocatalytic system composed of Fe/Ti substances in the waste stream serves to further accelerate pollutant release. This study thoroughly investigates the primary causes of environmental pollution during the stockpiling of tunnel slag and assesses the potential environmental impact scenarios. The outcomes of this research offer substantial theoretical and empirical support for the management of slag generated during the tunnel construction process. [ABSTRACT FROM AUTHOR]

Chalcopyrite ores are processed mostly by pyrometallurgical techniques due to the refractory nature of the mineral to the current hydrometallurgical techniques. In order to overcome such refractoriness, pretreatment steps such as sulfurization may be applied to produce different copper phases and therefore improve the metal dissolution in the leaching step. The current study investigated the reaction products of the reaction between chalcopyrite and elemental sulfur at different chalcopyrite/sulfur ratios (1/1 and 1/2), reaction time (60 min and 90 min), and temperature (350ºC, 400°C and 450ºC). The sulfurization experiments revealed that covellite, nukundamite, bornite, and pyrite-like compounds were produced according to the experimental conditions applied. Then, the sulfurization products were submitted to chemical leaching tests at temperatures ranging from 32ºC to 70ºC, whereas bioleaching tests were also carried out with Acidithiobacillus ferrooxidans, at 32ºC. In the chemical leaching experiments at 70ºC, only 14% copper was recovered from the original chalcopyrite sample while the maximum copper extraction was 78% from bornite produced at 450ºC (90 min and mass ratio of chalcopyrite/sulfur of 1/2). On the other hand, copper extraction achieved 96% from the same sulfurization product containing synthetic bornite within 20 days of bioleaching. Bioleaching of the original chalcopyrite sample implied in a copper recovery of only 25% in the same period. Summarizing, the current work showed that chalcopyrite sulfurization at 450ºC was able to transform chalcopyrite into a bornite-like phase, which was chemically leached and bioleached by At. ferrooxidans. [ABSTRACT FROM AUTHOR]

The Jianbeigou gold deposit is a typical lode gold deposit in the Qinling metallogenic belt, located on the southern margin of the North China Craton. Three stages of the hydrothermal process can be distinguished, including the quartz ± pyrite, quartz‐polymetallic sulfide, and quartz‐carbonate ± pyrite stages. From the early to late stages, the homogenization temperatures of primary fluid inclusions are 281–362°C, 227–331°C, and 149–261°C, respectively. The corresponding salinities estimated for these fluids are 3.9–9.9 wt%, 0.4–9.4 wt%, and 0.7–7.2 wt% NaCl equiv. Combined with laser Raman spectroscopy data, the ore‐forming fluid belongs to a H2O‐CO2‐NaCl ± CH4 system with medium–low temperature and salinity. The δ18Ofluid and δD values for the quartz veins are –1.0‰ to 6.0‰ and –105‰ to –84‰, respectively, which indicates that the ore‐forming fluid is of mixed source, mainly derived from magma, with a contribution from meteoric water. Pyrite has been identified into three generations based on mineral paragenetic sequencing, including Py1, Py2, and Py3. The pyrites have δ34S sulfur isotopic compositions from three stages between 3.7‰ and 8.4‰, indicating that sulfur mainly originated from magma. Te, Bi, Sb, and Cu contents in pyrite were all high and showed a strong correlation with Au concentrations. Native gold and the Au‐Ag‐Bi telluride minerals were formed concurrently, and the As concentration was low and decoupled from the Au content. Therefore, Te, Bi, Sb and other low‐melting point chalcophile elements play an important role for gold mineralization in arsenic‐deficient ore‐forming fluid. Combined with the geological setting, evolution of pyrite, and ore‐fluids geochemistry, we propose that the Jianbeigou deposit can be classified as a magmatic–hydrothermal lode gold deposit. Gold mineralization on the southern margin of the North China Craton is related to Early Cretaceous magmatism and formed in an extensional setting. [ABSTRACT FROM AUTHOR]

Copper slag is a residue from the copper smelting process that not only takes up large amounts of space, but also contains harmful elements that can cause environmental pollution. In this paper, zinc in copper slag is sulfide-roasted using pyrite as a vulcanizing agent and anthracite and K2CO3 as additives, thus leaving zinc in the slag mainly in the form of ZnS. After sulfurization roasting, the slag can be stripped of Zn by flotation, and the remaining iron can be further applied in the blast furnace ironmaking process. The effects of temperature, holding time, pyrite addition, and K2CO3 addition on the Zn sulfation rate were investigated. The results showed that when pyrite, anthracite, and K2CO3 were added to the slag in amounts of 35, 2, and 10 pct of the slag's original mass, respectively, the total Zn in the slag was 3.16 pct, and its sulfuration rate was 83.5 pct. When pyrite was used to sulfide and dezincify copper bottom-blown smelting slag, the ZnO content in the slag was effectively reduced in preparation for subsequent ironmaking after flotation. This approach not only solves the problem of large piles of copper slag that cannot be fully utilized, but also alleviates the current shortage of iron ore in China. [ABSTRACT FROM AUTHOR]

The Xiling Gold Mine is a world-class giant monolithic gold deposit with an average gold content of 3.81 g/t, offering significant mining value. Utilizing techniques such as optical microscopy, scanning electron microscopy, and the mineral automatic analysis instrument(AMICS), the process mineralogical characteristics of the ore from the Xiling Gold Mine were analyzed, including an examination of mineral composition, dissemination grade, existence state of gold and its carrier minerals, and other pertinent features. The results indicate that gold in the ore primarily exists in the form of native gold and electrum. The majority of metal minerals are pyrite, accompanied by small quantities of sphalerite, chalcopyrite, galena, and arsenopyrite. Non-metallic minerals are predominantly quartz followed by muscovite, orthoclase, and potassium feldspar. Gold minerals within the ore mainly occurred in exposed gold form with a dissemination grain size concentrated above 10 µm. There is a close relationship between gold minerals and pyrite regarding their dissemination patterns; pyrite exhibits relatively coarse dissemination grain sizes, and the gold can be easily recovered under appropriate grinding fineness conditions at suitable reagent dosages during processing using full sulfide flotation technology. Based on the results of the process mineralogy analysis, the Xiling gold mine was processed using the full sulfide flotation process. The results of the closed -- circuit flow test show that under appropriate grinding fineness and reagent system conditions, the mineral processing indicators of Au 62.77 g/t with an Au recovery rate reaching 98. 89% can be achived. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) in environments with temperatures below 100 °C is generally assumed to be of microbial origin, while abiotic H2S production is typically restricted to higher temperatures (T). In this study, we report an abiotic process for sulfidogenesis through the reduction of elemental sulfur (S0) by hydrogen (H2), mediated by pyrite (FeS2). The process was investigated in detail at pH 4 and 80 °C, but experimental conditions ranged between 40 and 80 °C and pH 4–6. The experiments were conducted with H2 as reducing molecule, and µm-sized spherical (but not framboidal) pyrite particles that formed in situ from the H2S, S0 and Fe2+ present in the experiments. Fe monosulfides, likely mackinawite, were identified as potential pyrite precursors. The absence of H2 production in controls, combined with geochemical modelling, suggests that pyrite formation occurred through the polysulfide pathway, which is unexpected under acidic conditions. Most spherical aggregates of authigenic pyrite were composed of nanometric, acicular crystals oriented in diverse directions, displaying varying degrees of organization. Although it was initially hypothesized that the catalytic properties were related to the surface structure, commercially sourced, milled pyrite particles (< 50 μm) mediated H2S production at comparable rates. This suggests that the catalytic properties of pyrite depend on particle size rather than surface structure, requiring pyrite surfaces to act as electron shuttles between S0 and H2. [ABSTRACT FROM AUTHOR]

This current study explored the effect of pyrite on the treatment of chlorophenolic compounds (CP) by Fenton process with micron-sized zero-valent iron (ZVI) as the catalyst. The experiments were conducted in batch reactors with 100 mg L−1 CP, 0–0.02 M H2O2, and variable pyrite and ZVI doses (0–1 g L−1). Our findings show that while the reactor with 1 g L−1 ZVI as the only catalyst achieved only 10% CP removal efficiency due to rapid ZVI surface passivation and ZVI particle aggregation, the CP removal efficiency increased with increasing pyrite dose and reached 100% within couple of minutes in reactors with 0.8 g L−1 pyrite and 0.2 g L−1 ZVI. The CP removal was mainly driven by the oxidative treatment of CPs with some strong radicals such as hydroxyl radicals (•OH) while the adsorption onto the catalyst surface was only responsible for 10 to 25% of CP removals, depending on the type of CP studied. The positive impact of pyrite on CP removal by the ZVI/H2O2 system could be attributed to the ability of pyrite to (1) create an acidic environment for optimum Fenton process, (2) provide support material for ZVI to minimize ZVI particle agglomeration, and (3) stimulate iron redox cycling for improved surface site generation. Following oxidative Fenton treatment, the degradation intermediate products of CPs, including some aromatic compounds (benzoquinone, hydroquinone, etc.) and organic acids (e.g., acetic acid), became more biodegradable in comparison to their mother compounds. Overall, the treatment systems with a mixture of ZVI and pyrite as catalyst materials could offer a suitable cost-effective technology for the treatment of wastewater containing biologically non- or low-degradable toxic compounds such as chlorophenols. [ABSTRACT FROM AUTHOR]

Mesozoic oceanic anoxic events were characterized by relatively low seawater sulphate concentrations ([SO42−$$ {{\mathrm{SO}}_4}^{2-} $$]), which likely regulated the development and evolution of these major palaeoceanographic phenomena. However, there is little reliable sedimentary evidence for low [SO42−$$ {{\mathrm{SO}}_4}^{2-} $$] in ancient marine waters and understanding of how such a seawater chemistry potentially impacted oceanic anoxic events is limited. This study presents an integrated sedimentological, mineralogical and geochemical investigation of the mineral siderite hosted in dark grey shale and sideritic concretions of Early Aptian (coeval with Oceanic Anoxic Event 1a) from the Tibetan Himalaya. Siderite is present throughout the section and possesses similar morphological characteristics whether in dark grey shale or concretions. Siderite can be present as disseminated and rhombic crystals formed during early diagenesis, or minor spherical crystals formed during late diagenesis. The evidence from redox elements, middle rare‐earth element bulge patterns and extremely low carbon‐isotope values of the sideritic concretions indicates that the iron carbonate was formed in the Fe‐reduction zones by the process of dissimilatory iron reduction. This process would have required conditions of low [SO42−$$ {{\mathrm{SO}}_4}^{2-} $$], reducing environment, abundant iron and high alkalinity. Additionally, the coexistence of siderite and pyrite may indicate that dissimilatory iron reduction occurred close to the microbial sulphate reduction zone, with seawater [SO42−$$ {{\mathrm{SO}}_4}^{2-} $$] hovering around the tipping point at which pyrite could form once seawater sulphate increased. Such an increase during Oceanic Anoxic Event 1a could have resulted from basalt–seawater interaction and associated enhanced continental weathering, and/or hydrothermal activity. This study's observations support the previous hypothesis that low [SO42−$$ {{\mathrm{SO}}_4}^{2-} $$] for Oceanic Anoxic Event 1a was probably caused by massive gypsum burial in the proto‐South Atlantic. Subsequently, enhanced sulphate input could have promoted microbial sulphate reduction and accompanying oxidation of organic matter, which likely further enhanced nutrient recycling, increased primary productivity and organic‐carbon burial, leading to more oxygen consumption and expansion of oxygen minimum zones, as reconstructed for many oceanic anoxic events. [ABSTRACT FROM AUTHOR]

Owing to the impact of the effluent C/N from the secondary structures of urban domestic wastewater treatment plants, the denitrification efficiency in constructed wetlands (CWs) is not satisfactory, limiting their widespread application in the deep treatment of urban domestic wastewater. To address this issue, we constructed enhanced CWs and conducted orthogonal experiments to investigate the effects of different factors (C/N, fillers, and plants) on the removal of conventional pollutants and the reduction of greenhouse gas (GHG) emission. The experimental results indicated that a C/N of 8, manganese sand, and calamus achieved the best denitrification efficiencies with removal efficiencies of 85.7%, 95.9%, and 88.6% for TN, NH4+-N, and COD, respectively. In terms of GHG emission reduction, this combination resulted in the lowest global warming potential (176.8 mg/m2·day), with N2O and CH4 emissions of 0.53 and 1.25 mg/m2·day, respectively. Characterization of the fillers revealed the formation of small spherical clusters of phosphates on the surfaces of manganese sand and pyrite and iron oxide crystals on the surface of pyrite. Additionally, the surface Mn (II) content of the manganese sand increased by 8.8%, and the Fe (III)/Fe (II) and SO42−/S2− on pyrite increased by 2.05 and 0.26, respectively, compared to pre-experiment levels. High-throughput sequencing indicated the presence of abundant autotrophic denitrifying bacteria (Sulfuriferula, Sulfuritalea, and Thiobacillus) in the CWs, which explains denitrification performance of the enhanced CWs. This study aimed to explore the mechanism of efficient denitrification and GHG emission reduction in the enhanced CWs, providing theoretical guidance for the deep treatment of urban domestic wastewater. [ABSTRACT FROM AUTHOR]

Pyrite is a ubiquitous sulfide mineral found in diverse geological settings and holds great significance in the formation of Au deposits as well as the safe utilization of groundwater due to its remarkable ability to incorporate substantial amounts of As. However, despite its importance, there remains a dearth of fundamental data on the partitioning of As between pyrite and fluid, which is key for accurately modeling the As distribution in these environments. Here, we present new insights into the partitioning behavior of As between pyrite and fluid at conditions that mimic natural fluid systems. Pyrite was synthesized by replacement of natural siderite in hydrothermal experiments at 200 °C and pH 5 applying a wide range of fluid As concentrations, spanning from 0.001 to 100 µg/g. The As distribution and concentration in synthetic pyrite was analyzed by quantitative LA-ICP-MS mapping providing a high spatial resolution and sensitivity at 2–3 µm image pixel size at a detection limit of ∼1 µg/g at the single pixel scale. Pyrite-fluid partitioning coefficients (D As (py/fluid)) between synthetic pyrite and experimental fluid agree with previously published data for high fluid As concentrations of 1 µg/g to 100 µg/g (D As < 2000). However, at low As concentrations in the experimental fluid (<1 µg/g), a steep increase in the D As (py/fluid) values of up to ∼30,000 was detected, demonstrating even stronger As partitioning into pyrite. This is confirmed by the analyses of natural pyrite that precipitated from As-poor fluids (0.3–0.4 ng/g) within a deep anoxic aquifer in SE Sweden. The discovery holds significant implications for the mobility and scavenging of As, which in turn is important for understanding the formation and fingerprinting of mineral deposits as well as for the secure utilization of groundwater resources. [ABSTRACT FROM AUTHOR]

In the formerly glaciated terrains in the northern hemisphere and countries such as Finland, till is the most common sediment covering the bedrock. Specifically, indicator or heavy mineral studies utilising till as a vector for mineral deposits undercover have been successful. The pyrite trace-element composition from in situ mineral analyses has been shown to be an effective discriminator between different mineral deposit types, and this has led to research using heavy mineral pyrite in till to identify potential mineral deposits in a given area. However, pyrite is easily oxidised in till beds, and thus, alternative methods should be considered. Goethite pseudomorphs are more commonly found in the till sediments as remnants after pyrite oxidation. This study evaluates trace element compositions of goethitised pyrite recovered in the till beds from central Lapland in northern Finland. Intra-grain trace-elemental variations gathered using laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) between the intact pyrite core and oxidised rim demonstrated complex dynamics and variations between different trace-element values. For example, Cu, V and Mn exhibited elevated trace-element values in the goethite rim compared to the pyrite core. However, elemental ratios such as Ni/As and Co/Ni remain stable between the pyrite core and oxidised rim. Therefore, these ratios have the potential to be used as a discriminating tool between the pyrite core and oxidised rim. In addition, nanoscale variabilities using focused ion beam (FIB) and transmission electron microscopy (TEM) were utilised to inspect possible nano inclusions within the studied heavy mineral grain. The FIB and TEM studies revealed a nanocrystalline pyrite nodule observation within the goethite rim. [ABSTRACT FROM AUTHOR]

This document is an editorial for a special issue on "Valuable Metals Recovery by Mineral Processing and Hydrometallurgy." It emphasizes the importance of metals for society and the need for efficient techniques to process ores and extract metals. The recovery of metals from secondary sources, such as mining waste, is also highlighted. The editorial discusses various aspects and challenges of metal recovery, including the use of flotation in mineral beneficiation and the application of hydrometallurgical methods. It presents studies on grinding media, pulp oxidation-reduction potential, and the use of new reagents for metal recovery. The editorial also explores the extraction of metals from refractory ores and mining waste. Overall, the papers in this special issue demonstrate the potential for recovering valuable metals from various sources using modern techniques and theoretical frameworks. [Extracted from the article]

Industrial activities have historically generated significant quantities of by-products, including pyrite cinders, a residue produced during the synthesis of sulphuric acid. This study presents a multidisciplinary approach to characterise an abandoned pyrite cinder deposit. Combining geophysical (electrical resistivity tomography—ERT), geochemical, and statistical methods, we assess the physicochemical properties of the deposit and its environmental implications. Our findings reveal the presence of heavy metals, with lead (7017.5 mg.kg−1) being the most concentrated element on the surface of the deposit, exceeding local legal thresholds by more than 163 times, posing environmental risks and inhibiting vegetation growth. Subsurface characterisation indicates a decreasing concentration trend of metals with depth, alongside variations in pH and electrical conductivity. Clustering analysis identifies groups of similar behaviours between resistivity, the most abundant heavy metals, and other variables, providing valuable insights into the complex interplay within the deposit. Our study underscores the importance of integrated approaches in assessing and managing hazardous waste sites, with implications for environmental remediation strategies. [ABSTRACT FROM AUTHOR]

The Wadi Ranga sulfidic jasperoids in the Southern Eastern Desert (SED) of Egypt are hosted within the Neoproterozoic Shadli metavolcanics as an important juvenile crustal section of the Arabian Nubian Shield (ANS). This study deals with remote sensing and geochemical data to understand the mechanism and source of pyritization, silicification, and hematization in the host metavolcanics and to shed light on the genesis of their jasperoids. The host rocks are mainly dacitic to rhyolitic metatuffs, which are proximal to volcanic vents. They show peraluminous calc-alkaline affinity. These felsic metatuffs also exhibit a nearly flat REE pattern with slight LREE enrichment (La/Yb = 1.19–1.25) that has a nearly negative Eu anomaly (Eu/Eu* = 0.708–0.776), while their spider patterns display enrichment in Ba, K, and Pb and depletion in Nb, Ta, P, and Ti, reflecting the role of slab-derived fluid metasomatism during their formation in the island arc setting. The ratios of La/Yb (1.19–1.25) and La/Gd (1.0–1.17) of the studied felsic metatuffs are similar to those of the primitive mantle, suggesting their generation from fractionated melts that were derived from a depleted mantle source. Their Nb and Ti negative anomalies, along with the positive anomalies at Pb, K, Rb, and Ba, are attributed to the influence of fluids/melt derived from the subducted slab. The Wadi Ranga jasperoids are mainly composed of SiO2 (89.73–90.35 wt.%) and show wide ranges of Fe2O3t (2.73–6.63 wt.%) attributed to the significant amount of pyrite (up to 10 vol.%), hematite, goethite, and magnetite. They are also rich in some base metals (Cu + Pb + Zn = 58.32–240.68 ppm), leading to sulfidic jasperoids. Pyrite crystals with a minor concentration of Ag (up to 0.32 wt.%) are partially to completely converted to secondary hematite and goethite, giving the red ochre and forming hematization. Euhedral cubic pyrite is of magmatic origin and was formed in the early stages and accumulated in jasperoid by epigenetic Si-rich magmatic-derived hydrothermal fluids; pyritization is considered a magmatic–hydrothermal stage, followed by silicification and then hematization as post-magmatic stages. The euhedral apatite crystals in jasperoid are used to estimate the saturation temperature of their crystallization from the melt at about 850 °C. The chondrite (C1)-normalized REE pattern of the jasperoids shows slightly U–shaped patterns with a slightly negative Eu anomaly (Eu/Eu* = 0.43–0.98) due to slab-derived fluid metasomatism during their origin; these jasperoids are also rich in LILEs (e.g., K, Pb, and Sr) and depleted in HFSEs (e.g., Nb and Ta), reflecting their hydrothermal origin in the island arc tectonic setting. The source of silica in the studied jasperoids is likely derived from the felsic dyke and a nearby volcanic vent, where the resultant Si-rich fluids may circulate along the NW–SE, NE–SW, and E–W major faults and shear zones in the surrounding metavolcanics to leach Fe, S, and Si to form hydrothermal jasperoid lenses and veins. [ABSTRACT FROM AUTHOR]

Shales of the Wufeng-Longmaxi formations in the basin-margin transition zone of southeastern Chongqing, China are characterized by high organic matter content and a significant presence of pyrite development. By examining numerous scanning electron microscope (SEM) images and considering the crystal and aggregate characteristics of minerals, we identified four types of pyrite in the study area: euhedral crystals, irregular aggregates, framboidal aggregates, and metasomatized organisms. Among these types, framboidal aggregates are the most prevalent. The formation mechanism of framboidal pyrite can be categorized into inorganic and organic origins. As inferred from the pyrite characteristics in the study area, the formation mechanism of the metasomatized organisms aligns with the biologically induced mineralization mode of organic origin, whereas the framboidal aggregates are more associated with the biologically controlled mineralization mode of organic origin. This underscores a close relationship between the pyrite formation and organic matter, which in turn indicates that an organic origin is more consistent with the pyrite characteristics observed in this study area. The pyrite morphology can reflect reactive iron concentration. Euhedral pyrite crystals tend to form under a low reactive iron concentration, whereas the formation of framboidal pyrite requires a high reactive iron concentration. Additionally, the type and grain size of pyrite aggregates can reflect variations in the redox conditions of the depositional environment. Pyrite produces positive effects on reservoir storage space, with intercrystalline organic pores, intercrystalline pores, and mold pores associated with pyrite contributing greatly to the storage spaces. [ABSTRACT FROM AUTHOR]

Cobalt is a critical metal widely distributed in nature, but cobalt ore has hardly been found as an independent mineral. Cobalt-bearing pyrite tailings separated from iron ore is one of the resources for recovering cobalt. In the following study, roasting is carried out to oxidize cobalt-bearing pyrite tailings for preparing and recovering the cobalt by acid leaching. The further aim of the research is to determine and control the optimal technological regime for roasting by using thermodynamic modeling. The phase transition in Fe–S–O and Co–S–O systems and its mechanism are analyzed under the partial pressure of oxygen and sulfur dioxide at constant temperatures. Thermodynamic modeling proves that iron and cobalt sulfides can be intensively oxidized at a relatively high temperature (>900 °C) under an atmosphere of logp(O2) > −5, leading to the formation of SO2 (logp(SO2) < 0). The results of the roasting experiment indicate 98% desulfurization degree upon holding for about 4–5 h and at > 1000 °C. Based on these thermodynamic modeling and experimental results, the roasting of cobalt containing pyrite can be optimized with substantial productivity with regard to the metal oxide and cobalt thereof. Oxidative roasting also allows the elimination of environmentally hazardous gases such as sulfur during the process. [ABSTRACT FROM AUTHOR]

Copyright of China Mining Magazine is the property of China Mining Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Activated persulfate systems with Fe-based catalysts in laboratory are reviewed. • The persulfate system activated by iron ore catalysts was introduced. • The advantages and disadvantages of two types of catalysts were discussed. • The mechanism of removing organic pollutants was evaluated. • The research direction of Fe-based catalyst/PS/ pollutant system was proposed. Heterogeneous iron-based catalysts have drawn increasing attention in the advanced oxidation of persulfates due to their abundance in nature, the lack of secondary pollution to the environment, and their low cost over the last a few years. In this paper, the latest progress in the research on the activation of persulfate by heterogeneous iron-based catalysts is reviewed from two aspects, in terms of synthesized catalysts (Fe0, Fe 2 O 3 , Fe 3 O 4 , FeOOH) and natural iron ore catalysts (pyrite, magnetite, hematite, siderite, goethite, ferrohydrite, ilmenite and lepidocrocite) focusing on efforts made to improve the performance of catalysts. The advantages and disadvantages of the synthesized catalysts and natural iron ore were summarized. Particular interests were paid to the activation mechanisms in the catalyst/PS/pollutant system for removal of organic pollutants. Future research challenges in the context of field application were also discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

The injection of CO2 into deep, unmineable coal seams is an effective strategy for reducing greenhouse gas emissions. At depths greater than 800 m, the carbon dioxide transitions to the supercritical state (Sc-CO2). This study investigated the complex interactions between Sc-CO2 and coal, which substantially affected the pore structure, mineralogy, and permeability of the coal. We used low-pressure nitrogen gas adsorption (LP-N2GA) to assess the impact of Sc-CO2 on the pore characteristics of the coal. X-ray diffraction (XRD) was also used to determine the causal factors. We performed comparative triaxial permeability tests before and after Sc-CO2 exposure to evaluate the changes in permeability for various coal types. Our findings suggested that Sc-CO2 exposure markedly increased the complexity of the coal pore structure, which in turn affects coal-rock permeability. Specifically, a 10-day exposure period resulted in considerable increases of 43.5% and 50.9% in the pore volume and the specific surface area, respectively, along with a slight increase of 0.01 nm in the average pore diameter. Furthermore, there were notable decreases in the contents of minerals such as kaolinite, calcite, and pyrite, with decreases of 1.5%, 2.8%, and 2.2%, respectively, whereas the quartz content increased by 3%, indicating that significant mineral dissolution influenced the pore structure. A significant positive correlation was observed between the loss of coal mass and the increase in permeability. The effects of Sc-CO2 were most pronounced in coals with low permeabilities, particularly during the initial phase of saturation. Subsequent saturation cycles and prolonged exposure resulted in a reduced rate for permeability enhancement, which eventually reached a plateau. This study underscores the critical role of Sc-CO2 in long-term geological CO2 storage and improved efficiency for coalbed methane production. [ABSTRACT FROM AUTHOR]

Thermoelectric materials possess the capability to convert electricity into heat and vice versa. The utilization of chlorofluorocarbons and hydrochlorofluorocarbons as thermal carrier agents in traditional cooling and air conditioning systems has sparked a surge in exploration toward pioneering refrigeration and spatial conditioning technologies. Chalcogenides, known for their capacity to amplify the thermoelectric efficiency of materials and their adaptability across a broad spectrum of temperatures, stand out as pivotal components in thermoelectric materials. Despite their existing suboptimal performance, these materials hold substantial promise as power generators and as solid-state Peltier coolers, attracting significant attention and positioning them as subjects ripe for further investigation. Categorized into alkali or alkaline earth, transition metal, and main-group chalcogenides, these materials and their respective subclasses are meticulously scrutinized to pinpoint the most suitable thermoelectric materials for specific applications with an optimal operational temperature span. In the quest for energy-efficient technologies characterized by simple designs, absence of moving components, and superior stability, thermoelectric materials play a crucial role. This review highlights the advancements in theoretical parameters as well as the figure of merit (ZT) of chalcogenide materials, emphasizing their device applications. These insights are intended to provide viable future approaches to mainstream thermoelectric materials. This review reveals that Cu2Se achieves a maximum ZT value of 2.66 at 1039 K, marking it as the top performer among transition metal chalcogenides. Conversely, SnSe, a main-group metal monochalcogenide, exhibits a ZT value of 2.8 at 773 K, whereas nanowires of the main group of bismuth chalcogenides exhibit a ZT value of 2.5 at 350 K. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mineral-activated perxymonosulfate (PMS) shows dewaterability and triclosan removal. • Iron-rich minerals are more economical than traditional sources of Fe2+. • Rheological test demonstrates that siderite/PMS can promote sludge fragmentation. • Siderite could release Fe2+ more sustainably to persistently produce free radicals. High water and pharmaceutical and care products (PPCPs) bounded in sludge flocs limit its utilization and disposal. The advanced oxidation process of perxymonosulfate (PMS) catalyzed by iron salts has been widely used in sludge conditioning. In this study, two iron-rich minerals pyrite and siderite were proposed to enhance sludge dewatering performance and remove the target contaminant of triclosan (TCS). The permanent release of Fe2+ in the activation of PMS made siderite more effective in enhancing sludge dewater with capillary suction time (CST) diminishing by 60.5 %, specific resistance to filtration (SRF) decreasing by 79.2 %, and bound water content (BWC) dropping from 37.1 % to 2.6 % at siderite/PMS dosages of 0.36/0.20 mmol/g-TSS after 20 min of pretreatment. Pyrite/PMS performed slightly inferior under the same conditions and the corresponding CST and SRF decreased by 51.5 % and 71.8 % while the BWC only declined to 17.8 %. Rheological characterization was employed to elucidate the changes in sludge dewatering performance, with siderite/PMS treated sludge showing a 48.3 % reduction in thixotropy, higher than 28.4 % of pyrite/PMS. Oscillation and creep tests further demonstrated the significantly weakened viscoelastic behavior of the sludge by siderite/PMS pretreatment. For TCS mineralization removal, siderite/PMS achieved a high removal efficiency of 43.9 %, in comparison with 39.9 % for pyrite/PMS. The reduction in the sludge solids phase contributed the most to the TCS removal. Free radical quenching assays and EPR spectroscopy showed that both siderite/PMS and pyrite/PMS produced SO 4 -· and ·OH, with the latter acting as the major radicals. Besides, the dosage of free radicals generated from siderite/PMS exhibited a lower time-dependence, which also allowed it to outperform in destroying EPS matrix, neutralizing the negative Zeta potential of sludge flocs, and mineralizing macromolecular organic matter. [ABSTRACT FROM AUTHOR]

The Yangla Cu skarn deposit is located in the central part of the Jinshajiang Suture Zone, southwest China, with a total reserve of 150 Mt Cu @ 1.03%. The newly discovered antimony orebodies at the depth of Yangla are strictly controlled by the stratum, structure, and lithology, which are lenticular and vein-like within the marble fracture zone, which can provide a window into multistage mineralization and ore genesis at Yangla. Mineralization can be divided into three types, Cu–Pb–Zn (skarn) pyrite, galena, and sphalerite, Cu (porphyry) chalcopyrite and pyrite, and Sb (hydrothermal) stibnite and pyrite. The mineral assemblages were stibnite + pyrite + calcite + quartz ± minor scheelite in antimony ores. This study presents quantitative measurements of the trace element compositions of pyrite and stibnite from the Yangla antimony ores. Analysis of pyrite with electron probe microanalysis (EPMA) showed enrichment in Co, Ni, Sb, As, and Mo, and deficit in its S and Fe contents when compared to the stoichiometric concentrations of S and Fe in pyrite. The Sb-related pyrite may belong to sedimentary-reworked genesis and may be modified by hydrothermal fluids, thereby presenting a certain difference (i.e., crystal morphology, texture, and chemical composition) compared to the skarn and porphyry Cu-related pyrite in the Yangla Cu skarn deposit. Analysis of stibnite with EPMA and inductively coupled plasma-mass spectrometry showed enrichment in As, Pb, Sn, Pb, Cu, and Zn, and presented much higher Sb contents and slightly lower S contents when compared to the stoichiometric concentrations of Sb and S in stibnite. Statistical analysis of the stibnite trace elements showed correlations for the elemental pairs Cu–Pb, As–Sb, and Sn–Pb, and the coupled substitution equations Sb3+ ↔ Cu+ + Pb2+, Sb3+ ↔ As3+, and Sn2+ ↔ Pb2+ may be the major factors governed the incorporating Cu, Pb, As and Sn within the stibnite. Moreover, this study preliminary shows that the antimony mineralization may belong to a carbonate replacement hydrothermal genesis at Yangla. [ABSTRACT FROM AUTHOR]

This study presents the sulfur isotopic characteristics in baryte from carbonatites of the Sallanlatva massif and sulfides (mainly pyrite and pyrrhotite) from carbonatites, phoscorites and products of their contact interaction with the host silicate rocks of most carbonatite-bearing complexes of the Devonian Kola Alkaline Province (KAP). For some complexes (Ozernaya Varaka, Kontozero), these characteristics are reported for the first time. The determined range of δ34S variations of sulfides in one complex does not exceed 4‰, but reaches 20‰ for the entire Kola Alkaline Province. This may be related to the evolution style of carbonatites and associated rocks. It is shown that the δ34S value in sulfides decreases from (1) the least evolved volcanic carbonatites of the Kontozero complex (δ34Savg. = –1.3‰) through (2) carbonatites and phoscorites of the Kovdor, Ozernaya Varaka, Sokli, and Salmagora massifs towards (3) the rocks of Seblyavr, Vuoriyarvi, and, finally, the carbonatites of Sallanlatva (δ34Savg. = –14.7‰) massifs, where sulfides differ from those of other KAP carbonatites in their exceptionally low δ34S values. The carbonatite volcanics of Kontozero are almost barren of REE mineralization; carbonatites of the second group contain accessory amounts of REE minerals; the third group is peculiar in the abundance of late carbonatites, where REE carbonates are frequently major minerals. Thus, the greater the volume of REE minerals in carbonatites of the complex, the lower the δ34S value in sulfides from its carbonatites and associated rocks. For the first time in the KAP, the sulfur isotopic composition of associated baryte–pyrite pairs was studied in the Sallanlatva carbonatites. The sulfur isotopic characteristics are shown to correspond to the final low-temperature (250–350°C) stage of carbonatite evolution in oxidized conditions, which satisfies the parameters of baryte crystallization. Since the studied samples of the Sallanlatva carbonatites are explosive breccias, the oxidized composition of fluids may indicate their phreatomagmatic nature, i.e., formation due to the interaction of intruded hot matter (melt/fluid) with meteoric waters. [ABSTRACT FROM AUTHOR]

Efficient separation of Carlin-type gold deposits is a challenge for the utilization of gold ores. The majority of gold in Carlin-type gold ores occurs as invisible gold within pyrite, resuiting in the poor crysta1lization of pyrite. The previous investigation has shown that oxidation caused the homogenization effect, thereby resuiting in adhesion, thus, deteriorafing the separation resuits of Carhn-type gold deposits. Based on the understanding of interacfions mechanssm between pyrite and dolomite,a technical prototype of "strengthening dsspersion" to opttmize the separation index of Carlintype gold deposits was preliminari1y proposed and highly selective reagents sodium amino phosphate was se!ected to realize the apphcation of the technical prototype, good separation indccators have been obtained in the laboratory. In this paper,the turbidity test was used to verify the effects of se!ected reagents on strengthening dispersion, meanwhlle, the artificial mixed ore and the real ores of high-and low-grade Carlin-type gold deposit were used to demonstrate the effect of reagent on mineral separation. The resuits showed that; sodium aminophosphate can achieve the expected goal of increasing the Fe and Au recovery in the concentrate, and decreasing the MgO floating ratio, whUe,increasing the Au enrichment ratio to about 3. 5. The above resuits show that sodium amino phosphate can improve the separation effidency between pyrite and dolomite by strengthening the dsspersion of oxidized pyrite and dolomite particles,so as to optimiie the flotation index of Carlintype gold mine. The prototype technology provides a reference for the development of effic!ent separation between pyrite and dolomite minera!s,and has the potential for popuiarizafion and apphcation. [ABSTRACT FROM AUTHOR]

Deep‐sea methane seeps are amongst the most biologically productive environments on Earth and are often characterised by stable, low oxygen concentrations and microbial communities that couple the anaerobic oxidation of methane to sulfate reduction or iron reduction in the underlying sediment. At these sites, ferrous iron (Fe2+) can be produced by organoclastic iron reduction, methanotrophic‐coupled iron reduction, or through the abiotic reduction by sulfide produced by the abundant sulfate‐reducing bacteria at these sites. The prevalence of Fe2+in the anoxic sediments, as well as the availability of oxygen in the overlying water, suggests that seeps could also harbour communities of iron‐oxidising microbes. However, it is unclear to what extent Fe2+ remains bioavailable and in solution given that the abiotic reaction between sulfide and ferrous iron is often assumed to scavenge all ferrous iron as insoluble iron sulfides and pyrite. Accordingly, we searched the sea floor at methane seeps along the Cascadia Margin for microaerobic, neutrophilic iron‐oxidising bacteria, operating under the reasoning that if iron‐oxidising bacteria could be isolated from these environments, it could indicate that porewater Fe2+ can persist is long enough for biology to outcompete pyritisation. We found that the presence of sulfate in our enrichment media muted any obvious microbially‐driven iron oxidation with most iron being precipitated as iron sulfides. Transfer of enrichment cultures to sulfate‐depleted media led to dynamic iron redox cycling relative to abiotic controls and sulfate‐containing cultures, and demonstrated the capacity for biogenic iron (oxyhydr)oxides from a methane seep‐derived community. 16S rRNA analyses revealed that removing sulfate drastically reduced the diversity of enrichment cultures and caused a general shift from a Gammaproteobacteria‐domainated ecosystem to one dominated by Rhodobacteraceae (Alphaproteobacteria). Our data suggest that, in most cases, sulfur cycling may restrict the biological "ferrous wheel" in contemporary environments through a combination of the sulfur‐adapted sediment‐dwelling ecosystems and the abiotic reactions they influence. [ABSTRACT FROM AUTHOR]

Protocell models play a pivotal role in the exploration of the origin of life. Vesicles are one type of protocell model that have attracted much attention. Simple single-chain amphiphiles (SACs) and organic small molecules (OSMs) possess primitive relevance and were most likely the building blocks of protocells on the early Earth. OSM@SAC vesicles have been considered to be plausible protocell models. Pyrite (FeS2), a mineral with primitive relevance, is ubiquitous in nature and plays a crucial role in the exploration of the origin of life in the mineral–water interface scenario. "How do protocell models based on OSM@SAC vesicles interact with a mineral–water interface scenario that simulates a primitive Earth environment" remains an unresolved question. Hence, we select primitive relevant sodium monododecyl phosphate (SDP), isopentenol (IPN) and pyrite (FeS2) mineral particles to build a protocell model. The model investigates the basic physical and chemical properties of FeS2 particles and reveals the effects of the size, content and duration of interaction of FeS2 particles on IPN@SDP vesicles. This deepens the understanding of protocell growth mechanisms in scenarios of mineral–water interfaces in primitive Earth environments and provides new information for the exploration of the origin of life. [ABSTRACT FROM AUTHOR]

Despite being a major cyanide species in the process water, it is unclear how iron cyanide influences pyritic gold ore flotation as well as how lead ions influence pyritic gold ore flotation in the presence of iron cyanide. This study aims at revealing the interaction of Fe(CN)63− and lead ions in pyrite flotation to investigate the strong depressing effect of Fe(CN)63− on pyritic gold ore flotation and the significant activating effect of lead ions on pyritic gold ore flotation in the presence of Fe(CN)63− using flotation, zeta potential measurement and surface analysis methods. The flotation results showed that upon 5 × 10−5 mol/L Fe(CN)63− addition, pyrite recovery drastically decreased from about 51.3% to 8.6%, while the subsequent addition of 9.5 × 10−4 mol/L lead ions significantly activated pyrite with the recovery increasing from 8.6% to 91%, which demonstrated that Fe(CN)63− strongly depressed pyrite flotation, while lead ions completely activated pyrite in the presence of Fe(CN)63−. Zeta potential measurement, surface analysis using Cryogenic X-ray photoelectron spectroscopy (Cryo-XPS) and electrochemical impedance spectroscopy (EIS) revealed that Fe(CN)63− depression was attributed to the chemical adsorption of Fe(CN)63− on iron sites of pyrite as Prussian Blue (Fe[Fe(CN)6]); however, this hydrophilic layer could be covered totally by lead ions which adsorbed on as lead hydroxide/oxide through electrostatic interactions, which resulted in the significant activation effect of lead ions. The results from this study will lead to improved flotation of gold associated with pyrite in gold flotation plants. [ABSTRACT FROM AUTHOR]

Minerals and/or their compositions (substituted minor elements) can become metastable in changing conditions or if formed outside of equilibrium. Unstable minerals undergo chemical and/or structural modifications at rates determined by re-equilibration processes, such as diffusion, coupled dissolution-reprecipitation and recrystallization. However, re-equilibrated domains with sharp contacts that lack porosity or deformation microstructures are difficult to reconcile with previously documented processes. In this study, we investigate the mechanism by which Au-rich pyrite re-equilibrates to Au-poor pyrite. Gold and As-rich {1 0 0} oscillatory bands are truncated by Au-As-poor pyrite along {1 0 0} re-equilibration interfaces. At the nanoscale, dislocations oriented consistently along <1 0 0>, are enriched in Ni, As, Cu, Sb, Pb, and Au. Dislocations are located at the re-equilibration interfaces between the Au-As-rich and Au-As-poor pyrite. Quantitative crystallographic orientation maps do not show the presence of deformation-related boundaries along the re-equilibration interfaces, indicating that the dislocations are not deformation-related but are misfit dislocations to accommodate for lattice stain between As-rich and As-poor pyrite. The co-location of steps along the re-equilibration interfaces and dislocations suggests that pyrite can re-equilibrate by the migration of dislocations. The process is likely driven by lattice strain minimisation induced by As impurities. Element transport is achieved by a two step process with (1) capture of impurities by dislocation-impurity pair diffusion during the migration of dislocations and (2) pipe diffusion along the dislocation network towards the exterior of the crystal. We propose that re-equilibration of Au-rich arsenian pyrite, and the resulting remobilisation of Au, can operate through a dislocation-mediated interfacial re-equilibration (DMIR) process. This new mechanism may be active in a range of mineral reactions, particularly in metamorphic settings where limited fluid availability precludes interface-coupled dissolution-reprecipitation processes. [ABSTRACT FROM AUTHOR]

The early Paleozoic Era (∼540–420 Ma) was an interval of profound biogeochemical changes including increasing oxygen (O 2) and the onset of bioturbation (sediment mixing by animals). It is hypothesized that incipient bioturbation caused a monotonic decrease in sedimentary burial of pyrite (FeS 2), which would have slowed atmospheric O 2 accumulation. However, pyrite accumulation can exhibit complex responses to dynamic, low-O 2 environmental conditions. To assess pyrite burial in a potential modern analogue to early Paleozoic environments, we collected sediment cores from the Chesapeake Bay, an estuary with multiple gradients in sulfate concentration, hypoxia intensity, organic carbon flux and lability, and bioturbation. Results indicate that pyrite accumulation is maximized not under strong sulfate depletion in highly reducing sediments, but rather in sediments that occupy the mid-range of sulfate–chloride ratios. This probably occurs through efficient replenishment of pore water sulfate and/or through the generation of sulfur redox intermediates, which promote pyrite formation via the polysulfide reaction pathway. In light of these results and in contrast to earlier models, we hypothesize that mild early Paleozoic bioturbation temporarily increased pyrite burial efficiency by stimulating higher sulfate reduction rates and increasing sedimentary sulfide retention. Compiled sulfur and carbon data from a geochemical database indicate that median sulfur-carbon ratios of fine-grained marine siliciclastic rocks increased from the Ediacaran through the Ordovician, then decreased and became much less variable from the Silurian onward. Thus, the Cambrian and Ordovician Periods may constitute a distinct interval of the Proterozoic-Phanerozoic transition in which bioturbation temporarily accelerated O 2 buildup. This transition probably ended in the Silurian, when p O 2 rose to sufficient levels to homogenize sedimentary carbon–sulfur cycling. [ABSTRACT FROM AUTHOR]