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Experimental investigation of the fractionation behavior of Cu isotopes during the replacement of pyrite by Cu-bearing sulfides (chalcopyrite, bornite, and chalcocite) was conducted under hydrothermal conditions. At the initial stages of the replacement reaction, small mounds of product formed on the pyrite surface; these mounds then grew and coalesced, progressively covering the pyrite grains as the reaction proceeded. Chalcopyrite, bornite, and chalcocite formed sequential monomineralic zones from the pyrite reaction front towards the solution. During the early stage of the reaction, Cu isotope fractionation between the solids and the aqueous solution (Δ65Cu solid-aqueous , Δ65Cu solid-aqueous = δ65Cu solid – δ65Cu aqueous) was approximately –0.6 ‰, similar to the calculated equilibrium Cu isotope fractionation factors between Cu-bearing sulfides (chalcopyrite, bornite, and chalcocite) and CuCl 2 –. However, the Δ65Cu solid-aqueous moved progressively further from equilibrium with prolonged reaction time, with fractionation factors ranging from approximately –0.6 ‰ to –1.2 ‰. We found that significant fractionation of Cu isotopes between the solid products and aqueous solution was mainly controlled by the amount of chalcopyrite that formed in the product layers. We interpret that the Δ65Cu solid-aqueous was controlled by the diffusion of aqueous Cu(I) species among the product layers and the changes in Cu redox state during the precipitation of chalcopyrite. These results imply that the δ65Cu values measured in sulfides from low-temperature hydrothermal deposits may be controlled by the local chemistry of the fluids in product layers that precipitate sulfides. This study highlights the importance of local fluid characteristics, such as redox conditions, metal speciation, and diffusion, in controlling isotope fractionation pathways during non-equilibrium mineral replacement. [ABSTRACT FROM AUTHOR]

During pyrite mining, tailings and waste residues are generated, and the oxidation of exposed metal sulfides leads to significant environmental issues such as acid mine drainage pollution. Studying the oxidation mechanism of pyrite is crucial for inhibiting or preventing the formation of acid mine drainage. Alkaline amino acids were used as electrolytes to explore the electrochemical oxidation mechanism of pyrite. Through electrochemical methods such as OCP, CV, Tafel polarization curve, LSV, and EIS, the electrochemical behavior of pyrite surfaces was measured, confirming the feasibility of pyrite oxidation in an alkaline amino acid system. The oxidation mechanisms of pyrite were consistent across the 3 alkaline amino acids, with the oxidation rate of pyrite following the order: lysine>arginine>histidine. [ABSTRACT FROM AUTHOR]

Yongxin Gold Deposit is located in the southern part of Duobaoshan Cu-Mo-Au metallogenic belt. To understand the genesis of the deposit and provide exploration insights, a study was conducted on the rare earth elements, micro-elements, and isotopic composition of gold-bearing pyrite. The results indicate that the chemical composition of pyrite shows enrichment in light REEs and depletion in heavy REEs, with a right-sloping REE distribution pattern. The pyrite is enriched in high-field-strength elements such as U, Th, Zr, and Hf, and depleted in large-ion lithophile elements like Ba and Sr. Ratios such as w(Hf)/w(Sm), w(Nb)/w(La), and w(Th)/w(La) suggest that the ore-forming fluid contained more Cl than F. A negative Eu anomaly and the absence of a Ce anomaly indicate that the ore-forming fluid formed under reducing conditions. Ratios like w(Y)/w(Ho), w(Zr)/w(Hf), and w(Nb)/w(Ta) suggest that the mineralization process did not involve external hydrothermal fluids, nor did metasomatism occur, with the ore-forming fluid closely related to both mantle and crustal sources. The sulfur isotopic characteristics indicate that the ore-forming materials originated from deeper sources. Genetic indicators such as w(Co)/w(Ni) and w(Fe)/w(S＋As) suggest that the deposit is of a meso-epithermal volcanic hydrothermal origin. Based on the magmatic origin, tectonic setting, diagenesis-mineralization age, metallogenic process, geochemical characteristics, and the main features of representative gold deposits in the region, it is concluded that Yongxin Gold Deposit belongs to a porphyry metallogenic system, forming during the Early Cretaceous as a meso-epithermal, relatively Cl-rich, weakly reducing gold deposit. [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]

Gold grains are observed in a variety of forms, such as coarse-liberated native gold grains, and ultra-fine grains associated with sulfide or non-sulfide mineral particles, in the form of solid solution in sulfide minerals, mainly pyrite. In the flotation of gold ores, bulk sulfide mineral flotation is generally applied to maximize gold recovery. This approach gives high gold recoveries, but it also causes the recovery of barren sulfide minerals (i.e., sulfide mineral particles with no gold content), which increases concentrate tonnage and transportation costs and reduces the grade sometimes to below the saleable limit (approx. 10 g/t Au). This study addresses the differences between gold-bearing and barren pyrite particles taken from various ore deposits and utilizes these differences for the selective flotation of gold-bearing pyrite. The laboratory scale flotation tests conducted on three pyrite samples having different cyanide soluble gold contents show that a selective separation between gold-bearing pyrite and barren pyrite particles could be achieved under specific flotation conditions. Gold recovery is correlated directly with the cyanide-soluble gold in the ore samples. Electrochemical experiments were conducted to elucidate the differences in surface properties of the two types of pyrite. The barren pyrite particles were more cathodic and prone to cathodic reduction of OH− and depressant ions on the surface, and they could be depressed effectively without significantly affecting the gold-bearing particles. [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]

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]

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]

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]

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]

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]

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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]

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]

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]

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]

In situ iron isotope ratios (δ56Fe) in sulfide measured by secondary ion mass spectrometry (SIMS) can provide valuable information on several of Earth's surface processes. SIMS relies on the use of a matrix‐matched reference material to correct for instrumental mass fractionation. To date Balmat pyrite has been widely used as a reference material, on the assumption of its homogeneous δ56Fe composition. However, several studies have reported divergent bulk δ56Fe values, which may jeopardise its use. Here, we combined bulk solution MC‐ICP‐MS and in situ SIMS δ56Fe measurements on two Balmat batches: the Balmat‐Original published in Whitehouse and Fedo (2007) and Balmat‐UNIL. Despite similar compositions, this study demonstrates the existence of two isotopically distinct Balmat populations. With respect to Balmat‐Original (δ56Fe = ‐0.39 ± 0.05‰, 2s), Balmat‐UNIL is isotopically 'lighter' with a bulk solution MC‐ICP‐MS composition of ‐1.46 ± 0.024‰. Additionally, Balmat‐UNIL has two subpopulations: the first is characterised by δ56Fe values of ‐1.46 ± 0.25‰, whereas the second agrees with the original Balmat batch. In each Balmat‐UNIL subpopulation, the intra‐grain and inter‐grain variabilities are sufficient to use Balmat as a reference material for δ56Fe isotope measurements by SIMS. This study revealed at least two end‐member compositions of Balmat pyrite and calls for a careful batch‐specific determination of bulk δ56Fe. [ABSTRACT FROM AUTHOR]

The oxidative flotation separation of chalcopyrite from pyrite in weak alkaline seawater solution was investigated using potassium ferrate (K2FeO4) as the oxidizing reagent. The optimal K2FeO4 concentration of 0.25 kg/t was found to strongly depress pyrite (from 88.05% to 7.92%) but insignificantly influence chalcopyrite (remaining at around 93%). K2FeO4 oxidized pyrite to form hydrophilic Fe2O3, Fe(OH)3, FeOOH, and Fe2(SO4)3 that covering on pyrite surface to prevent the adsorption of collector sodium butyl xanthate (SBX), thereby depressing pyrite flotation. Although a small amount of hydrophilic species was formed on chalcopyrite surface after the addition of K2FeO4, some hydrophobic substances such as S22-/Sn2-/S0 were also observed, resulting in an unaffected overall floatability. Further, density functional theory (DFT) calculation proved that the activity of Fe on chalcopyrite surface was much lower than that on pyrite. Therefore, this study provides a green way to separate chalcopyrite from pyrite effectively in a low-alkali seawater system, which is of significance to the separation of sulfide minerals in the fresh water-lack areas. [ABSTRACT FROM AUTHOR]

The Chemical Vapor Transport (CVT) Reaction is an important and efficient method of synthesizing pyrite crystals. CVT-grown pyrites have been comprehensively investigated for physical properties and elemental chemical compositions. However, the isotopic compositions have not been investigated. In this study, four series of pyrite crystals (PY3, PY4, PY5, and PY6) were synthesized using the CVT method, with PY5 undoped and the others doped with nickel. The synthesized crystals were characterized qualitatively with confocal laser Raman microspectroscopy and quantitatively by EMPA, LA-ICP-MS, SIMS, and IRMS. The synthetic products are irregular polycrystalline aggregates or cubic and octahedral monocrystals, with characteristic Raman bands at ~344 cm−1, ~380 cm−1/377 cm−1, ~427 cm−1/430 cm−1, and S/Fe weight and atomic ratios of 1.15–1.17 and 2.01–2.04, respectively, indicative of pyrite. The pyrites contain traces of inevitable impurities such as Si and Br. The nickel contents of Ni-doped pyrites are heterogeneous, 39–27 300 ppm for PY3, 24–21 700 ppm for PY4, and 57–2610 ppm for PY6. By comparison, the δ34S values obtained by SIMS are relatively homogeneous (PY3 = 17.3 ± 0.9‰, PY4 = 17.7 ± 0.8‰, PY5 = 17.9 ± 0.8‰, PY6 = 17.7 ± 0.6‰, ±2SD), and are consistent with IRMS δ34S values (17.8 ± 0.2‰ for PY3, 18.3 ± 0.9‰ for PY4, 18.2 ± 0.3‰ for PY5, 18.1 ± 0.1‰ for PY6, ±2SD). The homogeneity of 34S/32S suggests that CVT has the potential to synthesize reference materials for the determination of sulfur isotopic composition of pyrite using in situ techniques. Additionally, we also investigated the matrix effects of nickel in pyrite on the measurement of 34S/32S by SIMS, and a preliminary equation of Δ34S (‰) = −0.59 × Ni (wt%)0.27 (R2 = 0.3), where Δ34S is the discrepancy between in situ and bulk δ34S values, was derived for calibration. [ABSTRACT FROM AUTHOR]

There is still a lack of research on the effect of the S and Fe vacancy on the adsorption mechanism of peroxide (H2O2) on the pyrite surface. In this work, the adsorption of H2O2 molecules on the perfect and defective pyrite surface is simulated based on density functional theory (DFT). The results indicated that the adsorption energy of H2O2 molecules on the S‐vacancy surface is relatively lower than that on the perfect surface and dissociative adsorption entirely occurs, while the adsorption behavior of H2O2 molecules on the S‐rich pyrite surface has not occurred. When the H2O2 molecules are adsorbed on the Fe‐rich pyrite surface, two products appear, one with two OH− species and the other with an H2O molecule and an O atom. The analysis of the transition state (TS) found that the dissociation of the H2O2 molecule producing two OH− species that bond with two Fe atoms is more likely to occur. In addition, based on the coordination chemistry, it is demonstrated that Fe atoms are more reactive around an S vacancy than on a perfect surface. [ABSTRACT FROM AUTHOR]

Seafloor massive sulfides are modern analogues to ancient volcanogenic massive sulfide deposits, which are particularly enriched in volatile and precious metals (e.g., Te, Au, Ag, Cu, Bi, Se) in subduction-related settings. However, the sources of metals are still poorly constrained, and it remains elusive, whether magmatic volatile influx controls their distribution in submarine hydrothermal systems on the plate tectonic-scale. Here, we demonstrate, for the first time, that Te, As, and Sb contents as well as related Te/As and Te/Sb ratios vary systematically with the δ34S composition of pyrite and native S, as reported by high-resolution coupled SIMS δ34S and trace element LA-ICP-MS micro-analysis. The better correlation of element ratios (Te/As, Te/Sb) opposed to trace element contents (e.g., Te) with δ34S in pyrite demonstrates that element ratios provide a more robust record of magmatic volatile influx than their absolute contents. On this basis, we define a quantitative threshold of high Te/As (>0.004) and Te/Sb (>0.6) ratios in pyrite that are indicative of magmatic volatile influx to submarine subduction-related hydrothermal systems. Two-component fluid mixing simulations further revealed that <5 % of magmatic volatile influx drastically changes the Te/As (and Te/Sb) ratio of the modelled fluid, but only slightly changes its δ34S composition. This suggests that Te/As and Te/Sb ratios are more sensitive to a magmatic volatile influx into seawater-dominated hydrothermal systems than δ34S signatures if the magmatic volatile influx was low. Beyond this, our results demonstrate that magma-derived fluid mixing with seawater only has a negligible effect on the magmatic volatile record of Te/As and Te/Sb, while the S isotope system is prone for seawater overprinting leading to commonly ambiguous source signatures. Thus, Te/As and Te/Sb systematics in pyrite provide a robust proxy to evaluate the contribution of magmatic volatiles to submarine hydrothermal systems from the grain- to plate tectonic-scale. [ABSTRACT FROM AUTHOR]

Waste printed circuit boards (WPCBs) can be bioleached for Cu recovery, but lack of substrate for the bioleaching culture. In this study, using pyrite as a bacterial substrate for bioleaching WPCBs and recovering Cu was explored. The results showed that the WPCBs bioleaching using pyrite as the bacterial substrate was feasible. Mechanical crushing was a suitable WPCBs pretreatment method. The optimal WPCBs and pyrite pulp densities were respectively found to be 1.25% (w/v) and 1.0% (w/v), and the suitable nitrogen source ratio ((NH4)2SO4: (NH4)2HPO4) was deemed as 2 g/L: 2 g/L, achieving a Cu2+ leaching efficiency of 95.60 ± 1.57% in 14 d. Copper in the bioleaching solution can be directly recovery via electrodeposition. The Cu recovery efficiency in 60 min was up to 92.19 ± 1.35% under the optimal condition that the initial Cu2+ concentration and pH were respectively set at 7.34 g/L and 2.75, and the current density was set at 200 A/m2. Copper was found as the dominant metal in the cathode deposits, existing in the form of Cu and Cu2O. This work provided a novel approach for bioleaching WPCBs and recovering Cu. [ABSTRACT FROM AUTHOR]

The Baiyun gold deposit is a medium-sized deposit in northeastern Hubei around the southern margin of the Tongbai-Dabie metallogenic belt. However, its genesis has not been determined. The metallogenic process of the Baiyun gold deposit can be divided into three stages: quartz + feldspar, quartz + native gold + electrum + polymetallic sulfides, and quartz + pyrite + calcite + iron dolomite + illite. In this study, LA-ICP-MS was used for in situ trace element and isotope analyses in the main and late ore stage hydrothermal sulfides to evaluate the genesis and evolution of ore-forming fluids. Gold is positively correlated with Ag, Cu, Pb, Zn, and Te and the Co/Ni ratio is greater than 1. The S isotope values of Py1 and Py2 are −0.23–3.04‰ and 1.27–6.09‰, respectively. As mineralization progressed, S isotope values increased. In situ S isotope values of the two types of galena symbiotic with pyrite in the main metallogenic stage are 2.97–3.47‰. In situ Fe isotopic values of pyrite are −0.05–0.82‰; values in the two stages are similar without significant fractionation. We inferred that the Baiyun gold deposit formed via magmatic mineralization related to the subduction of the Pacific Plate during the Yanshanian. [ABSTRACT FROM AUTHOR]

The separation of rare earth ions (RE3+) from aqueous solutions poses a significant challenge due to their similar chemical and physical characteristics. This study presents a method for synthesizing hematite nanoparticles (Fe2O3 NPs) through the high-temperature phase transition of natural pyrite for adsorbing RE3+ from mine wastewater. The characteristics of Fe2O3 NPs were studied using XRD, SEM, BET, XPS, FTIR, and Zeta potential. The optimal condition for RE3+ adsorption by Fe2O3 NPs was determined to be at pH 6.0 with an adsorption time of 60 min. The maximum adsorption capacities of Fe2O3 NPs for La3+, Ce3+, Pr3+, Nd3+, Sm3+, Gd3+, Dy3+, and Y3+ were 12.80, 14.02, 14.67, 15.52, 17.66, 19.16, 19.94, and 11.82 mg·g−1, respectively. The experimental data fitted well with the Langmuir isotherm and pseudo-second-order models, suggesting that the adsorption process was dominated by monolayer chemisorption. Thermodynamic analysis revealed the endothermic nature of the adsorption process. At room temperature, the adsorption of RE3+ in most cases (La3+, Ce3+, Pr3+, Nd3+, Sm3+, and Y3+) onto Fe2O3 NPs was non-spontaneous, except for the adsorption of Gd3+ and Dy3+, which was spontaneous. The higher separation selectivity of Fe2O3 NPs for Gd3+ and Dy3+ was confirmed by the separation factor. Moreover, Fe2O3 NPs exhibited excellent stability, with an RE3+ removal efficiency exceeding 94.70% after five adsorption–desorption cycles, demonstrating its potential for the recovery of RE3+ from mine wastewater. [ABSTRACT FROM AUTHOR]

In this study, a pyrite‐based autotrophic denitrification (PAD) system, a polycaprolactone (PCL)‐supported heterotrophic denitrification (PHD) system, and a pyrite+PCL‐based split‐mixotrophic denitrification (PPMD) system were constructed. The pyrite particle size was controlled in 1–3, 3–5, or 5–8 mm in both the PAD and PPMD systems to investigate the effect of pyrite particle size on the denitrification performance of autotrophic or split‐mixotrophic bioreactors. It was found that the PAD system achieved the best denitrification efficiency with an average removal rate of 98.98% in the treatment of 1‐ to 3‐mm particle size, whereas it was only 19.24% in the treatment of 5‐ to 8‐mm particle size. At different phases of the whole experiment, the nitrate removal rates of both the PHD and PPMD systems remained stable at a high level (>94%). Compared with the PAD or PHD system, the PPMD system reduced the concentrations of sulfate and chemical oxygen demand in the final effluent efficiently. The interconnection network diagram explained the intrinsic metabolic pathways of nitrogen, sulfur, and carbon in the three denitrification systems at different phases. In addition, the microbial community analysis showed that the PPMD system was beneficial for the enrichment of Firmicutes. Finally, the impact mechanism of pyrite particle size on the performance of the PPMD system was proposed. Practitioner Points: The reduction of pyrite particle size was beneficial for improving the efficiency of the PAD process.The change in particle size had an effect on NO2−‐N accumulation in the PAD system.The accumulation of NH4+‐N in the PPMD system increased with the decrease in particle size.The reduction of pyrite particle size increased the production of SO42− in the PAD and PPMD systems.The correlations among the effluent indicators of the PAD and PPMD systems could be well explained. [ABSTRACT FROM AUTHOR]

Pyrite is a ubiquitous mineral in many ore deposits and sediments, and its trace element composition is mainly controlled by temperature, oxygen fugacity, pH, compositions of fluids, and host rock composition. A discriminant analysis (DA), based on multi-element compositions of pyrite, distinguishes iron oxide-apatite (IOA), iron oxide copper-gold (IOCG), skarn Cu-(Fe), porphyry Cu-Mo, orogenic Au, volcanic-hosted massive sulfide (VMS), sedimentary exhalative (SEDEX) deposits, and barren sedimentary pyrite. Testing of the DA classifier yields an accuracy of 98% for IOA, 96% for IOCG, 91% for skarn Cu-(Fe), 94% for porphyry Cu-Mo, 87% for orogenic Au, 84% for VMS, 96% for SEDEX, and 85% for barren sedimentary pyrite. Furthermore, neural network, support vector machine, and random forest, were performed for selecting the optimum classifier more accurately. In these three techniques, the support vector machine yielded the highest overall accuracy (98% for IOA, IOCG, skarn Cu-Fe, and porphyry Cu-Mo, and 97% for orogenic Au, VMS, SEDEX, and barren sedimentary pyrite) and thus is an appropriate technique in predicting pyrite types. [ABSTRACT FROM AUTHOR]

The quality of bauxite resources in China is deteriorating, and the high-grade bauxite resources are depleting day by day, the resource problem has become an important problem for the development of China's aluminum industry, and the high sulfur and high iron bauxite, which has not yet been exploded on an industrial scale, belongs to the difficult-to-use resources, and it has a huge potential industrial value, and it is of great theoretical and practical significance to carry out the basic research on desulfurization and removal of iron from high sulfur and high Hon bauxite. For the comprehensive development and utilization of high sulfur and high iron bauxite in Guangxi, a systematic test of desulfurization and Hon removal from bauxite was carried out by using the process of "suspension oxidation roasting-reduction roasting-magnetic separation", and the transformation of mineral phases in the roasting process was studied by using the methods of X-ray diffraction analysis (XRD), chemical phase analysis, and X-ray photoelectron spectroscopy (XPS), etc. The test was carried out on the basis of "suspension oxidation roasting-reduction roasting-magnetic separation" . The results showed that the main sulfur containing and iron-containing mineral is pyrite, the process of "suspension oxidation roasting-reduction roasting-magnetic separation" can simultaneously realize the efficient removal of sulfur and the enrichment and separation of Hon. Under the conditions of suspension oxidation roasting with roasting temperature 700 °C, roasting time 40 min, O2 concentration 40%, and the total gas volume 600 mL/min, an oxidized roasting product with S, of 0.396% and desulfurization rate of 98.10% can be obtained. Suspension reduction roasting was then carried out under the conditions of roasting temperature 550 °C, roasting time 20 min, CO concentration 20%, total gas volume 600 mL/min, and magnetic Held strength 150 kA/m, which resulted in an iron ore concentrate with TFe grade of 54.79% and aluminum-rich ore with St of 0.248%, TFe grade of 4.37% and Al2O3 content of 75.27%. This technology substantially increases the Al2O3 content of high sulfur high iron bauxite, which is conductive to the subsequent dissolution of bauxite and achieves the technical goal of desulfurization and removal of iron to raise aluminum content. This process provides a new technical way for the efficient utilization of this kind of difficult--to-process to select high sulfur high iron bauxite resources. [ABSTRACT FROM AUTHOR]

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The presence of pyrite poses a significant impediment to the comprehensive utilization of coal gangue, which is a prevalent solid waste in industrial production. However, the current efficacy of jig separation for pyrite in fine-grade coal gangue remains unsatisfactory. To investigate the influence of particle size distribution on the jig separation of pyrite in fine-grade coal gangue, the raw material was crushed to less than 2 mm using a jaw crusher and subsequently sieved to obtain its particle size distribution curve. Upon fitting the curve, it was observed that it tends towards the Rosin-Rammler (RRSB) and Fuller distributions. Leveraging these two-parameter distribution curves, adjustments were made to determine the mass within each particle size range before conducting thorough mixing followed by jig separation. The results indicate that for fine-grade gangue particles smaller than 2 mm, the RRSB distribution with a uniformity coefficient of n = 0.85 exhibits the most effective separation, although it is comparable to the separation achieved using the size distribution of raw ore. On the other hand, employing the Fuller distribution with modulus of distribution q = 1.5 yields superior separation performance. In comparison to the raw ore, the concentrate shows an increase in sulfur (S) and iron (Fe) content by factors of 3.4 and 2.4, respectively. Furthermore, compared to the RRSB distribution, there is an increase in S and Fe content by 1.91% and 2.30%, respectively; the contents of S and Fe in tailings is 0.71% and 2.72%, which can be directly used as raw materials for coating materials. Therefore, for fine-grade coal gangue particles, jigging under the Fuller distribution demonstrates better effectiveness than under the RRSB distribution. [ABSTRACT FROM AUTHOR]

Through microscopic analyses (e.g., organic macerals, thin section observation, scanning electron microscope (SEM) imaging of fresh bedding planes via argon ion milling, and energy spectrum tests) combined with Rock-Eval analyses, this study systematically investigated the organic matter and pyrites in the continental shales in the 3rd submember of the Chang 7 Member (Chang 7³ submember) in the Yanchang Formation, Ordos Basin and determined their types and the formation and evolutionary characteristics. The results are as follows. The organic matter of the continental shales in the Chang 7³ submember is dominated by amorphous bituminites and migrabitumens, which have come into being since the early diagenetic stage and middle diagenetic stage A, respectively. The formation and transformation of organic matter is a prerequisite for the formation of pyrites. The Ordos Basin was a continental freshwater lacustrine basin and lacked sulphates in waters during the deposition of the Chang 7 Member. Therefore, the syndiagenetic stage did not witness the formation of large quantities of pyrites. Since the basin entered early diagenetic stage A, large quantities of sulfur ions were released as the primary organic matter got converted into bituminites and, accordingly, pyrites started to form. However, this stage featured poorer fluid and spatial conditions compared with the syndepositional stage due to withdraw of water, the partial formation of bituminites, and a certain degree of compaction. As a result, large quantities of pyrrhotite failed to transition into typical spherical framboidal pyrites but grew into euhedral monocrystal aggregates. In addition, pyrites are still visible in the migrabitumens in both microfractures and inorganic pores of mudstones and shales, indicating that the pyrite formation period can extend until the middle diagenetic stage A. [ABSTRACT FROM AUTHOR]

In this study, the typical azo dye methyl orange (MO) was degraded by pyrite (FeS2) activated by hydrogen peroxide (H2O2). When [MO] = 0.1 mM, [FeS2] = 2.0 g/L and [H2O2] = 22 mM, 96.4% MO was removed in 120 min and the TOC removal rate was higher than 50%. HO• was the primary radical responsible for MO degradation. In addition, the acid condition promoted the degradation of MO in the FeS2/H2O2 system. MO in tap water and river water was not effectively degraded, whereas acidification could weaken the inhibitory effect on the FeS2/H2O2 system to enable the degradation of MO in tap and river water. The OD600 indicated that the solution was environmentally friendly after the reaction, and three degradation pathways of MO were discussed. In summary, Fe(II) could be dissolved from FeS2, which activated H2O2 to generate Fe(III) and HO•. FeS2 could reduce Fe(III) into Fe(II), thus realizing the Fe(III)/(II) cycle and efficiently activating H2O2 to degrade MO. [ABSTRACT FROM AUTHOR]

A polymetallic layer is usually developed at the bottom of the early Cambrian black shale in Guizhou Province. The mineral that makes up the polymetallic layer is related to the sedimentary facies. To analyze the differentiation mechanism between polymetallic deposits (Ni‐Mo and V), the Zhijin Gezhongwu profile located in the outer shelf and the Sansui Haishan V deposit located in the lower slope are selected to study the in situ sulfur isotopes and trace elements of pyrite. The results show that δ34S values of pyrite vary widely from −7.8 ‰ to 28 ‰ in the Gezhongwu profile, while the δ34S values are relatively uniform (from 27.8 ‰ to 38.4 ‰) in the Haishan profile. The isotopic S composition is consistent with the transition that occurs in the sedimentary phase from the shelf to the deep sea on the transgressive Yangtze platform; this indicates that the δ34SO42– values in seawater must be differently distributed in depositional environments. The sulfur in the Ni‐Mo layer is produced after the mixing of seawater and hydrothermal fluid, while the V layer mainly originates from seawater. Overall, the Ni‐Mo and V deposits have been differentiated primarily on the basis of the combined effect of continental weathering and hydrothermal fluid. [ABSTRACT FROM AUTHOR]

Pyrrhotite, especially the monoclinic type, is a promising material for removing Cr (VI) from wastewater and groundwater due to its high reactivity. However, the purity of the preparation monoclinic pyrrhotite from heated natural pyrite is not high enough, and the role of possible sulfur vacancies in pyrrhotite's crystal structure has been largely ignored in the removal mechanism of Cr (VI). In this work, we characterized the phase composition changes of annealed pyrite in inert gas and prepared high-purity (~ 96%) monoclinic pyrrhotite at the optimal condition. We found that it could remove 18.6 mg/g of Cr (VI) by redox reaction, which is the best value reported of natural pyrite-derived materials so far. As the reactive media material of simulated permeable reactive barrier, the service life of the high-purity monoclinic pyrrhotite column is 297 PV, which is much longer than that of the pyrite column (50 PV). A new founding is that S2− and S vacancy play the essential role during the redox reaction of pyrrhotite and Cr (VI). Monoclinic pyrrhotite had more S vacancy than hexagonal pyrrhotite and pyrite, which explained its superior Cr (VI) removal performance. [ABSTRACT FROM AUTHOR]

Concentrically zoned pyrite aggregates (CZPA) are common in sediment‐hosted massive sulfide (SHMS) deposits and have been widely used to interpret the ore‐forming processes. There is considerable uncertainty, however, over the formation of aggregates that are oscillatorily zoned and contain randomly‐orientated pyrite microcrystals. Guided by the results of examination of the micro‐textures of CZPA and in‐situ chemical analyses, we conducted a quantitative diffusion‐reaction simulation to assess the mechanism of CZPA formation. Our study shows that oscillatory zoning results from the feedback between the diffusion of reactants and the nucleation‐growth of Fe‐sulfides. Externally derived Fe2+ diffuses into the early diagenetic sediments containing decomposing organic matter (2CH2O + SO42− = 2HCO3− + H2S) and reacts with H2S to form a pyrite layer via an intermediate pathway (Fe2+ + H2S → FeS + 2H+, FeS + H2S → FeS2 + H2). This growth of pyrite layers depletes the local concentration of reactants and suppresses nucleation until the diffusive reaction front advances and another layer is formed. Intermediate phases, for example, mackinawite, nucleate instead of pyrite, because of their greater ease of nucleation due to the low surface tension, and lead to the domination of nucleation over growth. The nucleation of mackinawite and occurrence of siderite in the CZPA are consistent with a low temperature, high pH, anoxic early diagenetic environment. Our study demonstrates that CZPA in SHMS deposits are formed by intrinsic self‐organizational processes rather than by extrinsic changes of ore‐forming fluids. The CZPA in SHMS deposits are thus indicative of their diagenetic origin with Fe2+ infiltrated and diffused from hydrothermal fluids into the sediments. Plain Language Summary: Oscillatory zoning patterns are a phenomenon commonly encountered in scientific disciplines that include biology, geology, chemistry and atmospheric physics. To decipher these patterns, we employ a unifying principle that leverages a reaction‐diffusion approach and successfully replicate the textures observed in a massive sulfide deposit, via numerical simulations. In addition, we show that factors such as the concentration, distribution, and mobility of reactant species, such as the iron ion, sulfide, and organic matter in sediments, influence the texture of patterns at both the millimeter and nanometer scales. Our proposed numerical models yield results that closely align with the oscillatory zoning patterns observed in pyrite‐siderite from the Xinqiao massive sulfide deposit in Central China. The broader impact of this work lies in the development of a computer simulation‐based protocol, which sheds light on the processes forming massive sulfide deposits. This, in turn, has the potential to significantly aid the exploration for new metal and sulfide resources beneath the surface of the Earth. Key Points: Reactive‐diffusion simulations of the formation of concentrically zoned pyrite aggregates in sediment‐hosted massive sulfide depositsThe ore textures were the result of an intrinsic self‐organized process rather than extrinsic changes of chemical compositionsProtocols for deciphering diagenetic environments affected by the infiltration of Fe2+‐rich hydrothermal fluids [ABSTRACT FROM AUTHOR]

Pyrite swelling in soils below buildings is a major issue. It leads to severe deformations in floor foundations. A survey is carried out at a selected site in the city of Laval, Quebec, to assess the usefulness of ground-penetrating radar (GPR) to detect deformations that may be indicative of the presence of pyrite. Four soil samples are taken from the aforementioned site to determine the soil type below the concrete slab. The results indicate the presence of limestone, moor clay, and shale sediments, which are prone to pyrite swelling. The GPR data were collected using the GSSI SIR 4000 with a high frequency antenna and processed using RADAN software. The GPR data indicate the presence of severe deformation in many locations of the concrete slab. The most important wave reflections indicative of pyrite swelling are the rebar reflections, showing interesting pushed-up and dropped-down reflections. These reflections appear in two forms. The first is the attenuated reflections that may occur due to pyrite-rich materials. The second is the high amplitude reflections that occur because of the air void, which can be formed due to heaving the concrete slab because of pyrite swelling. As a result, GPR appears to be an effective method for assessing and mapping the effect of pyrite swelling below concrete slabs. [ABSTRACT FROM AUTHOR]

In this study, TiO2 nanoparticles were employed as a photocatalyst for the degradation of tetracycline (TC) under visible light irradiation. The TiO2 nanoparticles were decorated on natural pyrite (TiO2/NP) and characterized using XRD, FTIR, and SEM–EDX methods. This study evaluated the impacts of various operational parameters such as pH, catalyst dosage, initial TC concentration, and light intensity on TC removal. The findings revealed that under optimal conditions (pH 7, catalyst: 2 g/L, TC: 30 mg/L, and light intensity: 60 mW/cm2), 100% of TC and 84% of TOC were removed within 180 min. The kinetics of TC elimination followed a first-order model. The dominant oxidation species involved in the photocatalytic elimination of TC was found to be ·OH radicals in the TiO2/NP system. The reuse experiments showed the high capability of the catalyst after four consecutive cycles. This study confirmed that the TiO2/NP system has high performance in photocatalytic TC removal under optimized experimental conditions. [ABSTRACT FROM AUTHOR]

The present study is aimed to formulate a numerical model to simulate hydrogeochemical reactions controlling pyrite oxidation in unsaturated aquifers under non-uniform flow conditions. A coupled flow and multi-component transport model is solved using a finite difference scheme to simulate the concentration distribution of oxygen (O2), ferrous (Fe2+), ferric (Fe3+), sulphate (SO42−) and hydrogen (H+) ions. An attempt is made to quantify the transport characteristics of pyrite oxidation ions by analysing the spatial moments of concentration profiles. The simulation results suggest that the variable flow rate in the vertical direction significantly enhances the pyrite oxidation near the ground surface. Peak concentration of Fe2+, Fe3+, and SO42− near the ground surface is found to be approximately 2–3 times higher in the case of variable flow. The pH level near the ground surface drops considerably when variable flow conditions exist in the unsaturated zone. The variation in flow parameters such as porosity, and water saturation and reaction parameters such as oxygen diffusion rate and the oxygen consumption rate are found to affect the mass and mobility of Fe2+, Fe3+, and SO42− considerably. Although there has been substantial research on hydrogeochemical events associated with pyrite oxidation in the past, there has been very less focus on the transport qualities of the ions produced in groundwater. The mobility assessment of pyrite oxidation ions in aquifer presented in the study is beneficial to understand the groundwater quality risk associated with mining and to plan and implement effective remediation strategies for the restoration of affected aquifers. [ABSTRACT FROM AUTHOR]

In the current study, the leaching conditions of chalcopyrite/pyrite concentrate were optimized by sulfuric acid and hydrogen peroxide using response surface methodology (RSM). The optimal leaching conditions were found to be a sulfuric acid concentration of 150 g/L, a hydrogen peroxide volume of 350 mL, a temperature of 80 °C, a leaching time of 8h and a solid–liquid ratio of 0.52 g/mL. After analysis of variance (ANOVA), the sulfuric acid concentration and temperature were the most significant process variables for the leaching concentrations of both copper and iron. Under the optimum conditions, the recovery of copper and iron was 81.83% and 67.57%, respectively. [ABSTRACT FROM AUTHOR]

Electron backscatter diffraction (EBSD) methods are used to investigate the presence of microstructures in pyrite from the giant breccia-hosted Olympic Dam iron–oxide copper gold (IOCG) deposit, South Australia. Results include the first evidence for ductile deformation in pyrite from a brecciated deposit. Two stages of ductile behavior are observed, although extensive replacement and recrystallization driven by coupled dissolution–reprecipitation reaction have prevented widespread preservation of the earlier event. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) element maps of pyrite confirm that many pyrite grains display compositional zoning with respect to As, Co, and Ni, but that the zoning is often irregular, patchy, or otherwise disrupted and are readily correlated with observed microstructures. The formation of ductile microstructures in pyrite requires temperatures above ~260 °C, which could potentially be related to heat from radioactive decay and fault displacements during tectonothermal events. Coupling EBSD methods with LA-ICP-MS element mapping allows a comprehensive characterization of pyrite textures and microstructures that are otherwise invisible to conventional reflected light or BSE imaging. Beyond providing new insights into ore genesis and superimposed events, the two techniques enable a detailed understanding of the grain-scale distribution of minor elements. Such information is pivotal for efforts intended to develop new ways to recover value components (precious and critical metals), as well as remove deleterious components of the ore using low-energy, low-waste ore processing methods. [ABSTRACT FROM AUTHOR]

Highlights: arsenian pyrite and marcasite with pronounced chemical zoning are synthesized Au-As atomic clusters with probable composition of [AuAs10] form in pyrite incorporation of Au in As-rich pyrite proceeds via a reductive deposition mechanism in marcasite the Au and As concentrations are not correlated the "invisible" gold content in pyrite is dictated by the hydrothermal fluid chemistry Hydrothermal synthesis experiments were performed in order to quantify the states of Au and As in pyrite and marcasite. The experiments were performed at 350 °C/500 bar and 490 °C/1000 bar (pyrite–pyrrhotite buffer, C(NaCl) = 15 and 35 wt.%). The synthesis products were studied by EPMA, LA-ICP-MS, and EBSD. The EPMA was applied for simultaneous determinations of Au, As, Fe, and S, with a Au detection limit of 45–48 ppm (3σ). The analyses were performed along profiles across zonal grains. The concentrations of As and Au up to 5 wt.% and 8000 ppm, respectively, were determined in pyrite and up to 6 wt.% and 1300 ppm in marcasite. In pyrite, the Au concentration decreases with fluid salinity and temperature increases. Strong positive Au–As correlation and strong negative Au–Fe and As–S correlation were identified in pyrite. Comparison of the correlations with theoretical lines implies Au–As clustering. The cluster stoichiometry is inferred to be [AuAs10]. Most probably, As in pyrite presents in the form of clusters and in the As→S solid solution. Incorporation of Au in As-rich pyrite can be controlled by the reductive deposition mechanism. In marcasite, the concentrations of Au are not correlated with the As content. The [AuAs10] clusters enrich the {210}, {113}, and {111} pyrite faces, where the former exhibits the highest affinity to Au and As. The affinity of {110} and {100} forms to Au and As is lower. Implication of the experimental results to data for natural auriferous pyrite shows that the increase of Au content at C(As) > 0.5–1 wt.% is caused by the incorporation of the Au-As clusters, but not because of the formation of Au→Fe solid solution. Therefore, the concentration of "invisible" gold in pyrite is dictated solely by the hydrothermal fluid chemistry and subsequent ore transformations. [ABSTRACT FROM AUTHOR]

As important metal sulfides in the geochemical cycle of sulfur, the characteristics and formation processes of pyrites can provide useful clues regarding their environment. Based on previous findings, shale pyrites were divided into three major classes (euhedral pyrites, framboidal pyrites (framboids) and metasomatic pyrites) and six sub-classes in this study. At the microscopic scale, each type of pyrite is associated with a different formation process. Framboids are formed by burst nucleation in environments with a homogeneous distribution of nutrients while euhedral pyrites are usually formed on pre-existing sites (such as =FeS on the minerals surface) in the heterogeneous system. Metasomatic pyrites formed by the replacement of other ions in accountable material by iron ions and hydrogen sulfide ions in hydrothermal events. The morphology and isotope value of pyrite provide information to track the origins of their nutrient and characteristics of sulfur and iron pools. In addition, the trace element content of pyrite can serve as a proxy for paleo-ocean trace element abundance, indicating changes in atmospheric oxygen content. Additionally, pyrite can also serves as an indicator of shale gas reservoirs. [ABSTRACT FROM AUTHOR]

The depression of pyrite in the flotation separation of molybdenum-sulfur (Mo-S) mixed concentrate has become a significant issue. This study aimed to examine the process of separating molybdenite and pyrite in the presence of sodium humate (NaHA). The results of micro-flotation tests indicated that NaHA exhibited significant pyrite depression capabilities and displayed remarkable selectivity toward both pyrite and molybdenite. Real ore flotation experiments have shown that adding 22.5 mg/L of NaHA to the pulp of Mo-S mixed concentrate at a pH of 6.5, the flotation indexes achieved 46.01% Mo grade and 90.11% Mo recovery. It is noteworthy that the dosage of NaHA was significantly lower compared to the 505 utilized in the mineral processing plant. Contact angle measurements revealed that NaHA effectively increased the surface hydrophilicity of pyrite. Adsorption amount measurements, zeta potential measurements, and Fourier infrared spectroscopic (FT-IR) analysis indicated that the adsorption capacity of NaHA on pyrite was higher than on molybdenite. NaHA had a highly selective inhibitory capacity for Mo-S mixed concentrate and is an ideal separation depressant. [ABSTRACT FROM AUTHOR]

This article explores the use of visible light-assisted advanced oxidation processes (AOPs) to degrade sodium butylxanthate (SBX) in flotation wastewater. The study compares different oxidants and finds that periodate is the most effective for SBX removal. The introduction of visible light accelerates the activation of the oxidants on the surface of pyrite, making it a promising catalyst for wastewater treatment. This research offers a new approach to purifying flotation wastewater and highlights the potential of natural pyrite as a cost-effective catalyst. [Extracted from the article]

This study presents the results of a two-stage autoclave processing of a copper–arsenic concentrate. Copper concentrate is an important raw material to produce copper and other metals. However, in some cases, the concentrate may contain increased amounts of arsenic, which makes further processing difficult. Therefore, the development of modern hydrometallurgical methods for processing copper concentrate with a high arsenic content is an urgent task, which could lead to the optimization of the raw material processing process and the improvement of the quality of the concentrate. It has been established that the optimal conditions for the sequential two-stage autoclave processing of copper–arsenic concentrate are: t = 220–225 °C, τoxidation = 20 min, τtot = 90 min, Po2 = 0.4 MPa, and L:S = 10:1, [H2SO4]initial = 40 g/dm3; in this case, 85% of zinc, 44% of iron, and 78% of arsenic, respectively, are extracted into the solution during both stages and the loss of copper was about 0.01%. This is explained by the fact that at the first stage (oxidation) of the autoclave processing of the copper–arsenic concentrate, copper, together with iron, leaches into the solution, and at the second stage (reduction), copper precipitates out of the solution in the form of chalcocite. Copper in the residue after autoclave leaching is in the form of Cu2S, iron is in the form of pyrite (FeS2), and lead is in the form of anglesite (PbSO4), respectively. The obtained micrographs and EDX mappings clearly show no iron arsenates. This confirms that at the oxidative stage of the developed process, arsenic, removed by 78%, remains in the solution. The remaining arsenic is associated with tennantite, indicating the effectiveness of the treatment process in removing arsenic from the copper–arsenic concentrate. A second important observation is the presence of pronounced areas of copper sulfides in the microphotos without iron and arsenic impurities. This confirms that copper is deposited as chalcocite during the reduction phase of the process, which is the desired result. [ABSTRACT FROM AUTHOR]

Pyrite geochemistry is crucial for the discrimination of the types of ore-forming fluids in gold deposits, such as metamorphic–hydrothermal fluids and magmatic–hydrothermal fluids. With the assistance of supervised machine learning algorithms, this application can be leveraged maximally. Here, laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) geochemical data for 4683 pyrite samples worldwide were collected to train seven classification models. The top three algorithms, including Random Forest (RF), Support Vector Machines (SVM), and Multilayer Perceptron (MLP), were used to build classifiers to predict the type of pyrite. The established classifiers were applied to new geochemical data for pyrite samples collected from the Jinkeng and Huanggou gold deposits in the Xuefengshan Orogen (XFSO). The findings suggest that the classifiers are capable of accurately distinguishing between two main types of ore-forming fluids, with good predictive outcomes. This performance surpasses that of traditional, two-dimensional diagram-based methods. The classifiers determined that the geochemical constituents of pyrite from the Jinkeng and Huanggou originated from metamorphic–hydrothermal sources, consistent with geological and geochemical evidence. The results further reveal that the Jinkeng and Huanggou are classified mostly as orogenic gold deposit. This study proves that data-driven methods based on machine learning can provide compelling evidence for distinguishing between the types of ore-forming fluids, understanding deposit genesis, and providing prospecting ideas. Additionally, this research boosts confidence in the use of machine learning to geological classification challenges. [ABSTRACT FROM AUTHOR]