Pyrite Minerals Research Articles

Flotation separation of pyrite and carbonate minerals from a carlin-type gold deposit in Guizhou by a new combined collector and its adsorption mechanism

Flotation separation of pyrite and carbonate minerals from a carlin-type gold deposit in Guizhou by a new combined collector and its adsorption mechanism

Distribution of tellurium, selenium, cobalt and gold in sulfide minerals: A case study of the Jiguanzui porphyry-skarn Au-Cu deposit, eastern China

The Jiguanzui deposit is a representative porphyry-skarn Au-Cu deposit in the Mid-Lower Yangtze River metallogenic belt, Eastern China, characterized by significant critical metal (Te, Se, Co) association. Previous study focused on the Te and Se distribution in the ores and pyrite minerals on deposit scale, this study present trace element geochemistry of various sulfide minerals (chalcopyrite, bornite, sphalerite, molybdenite) through LA-ICP-MS analysis, aiming to reveal the distribution of Te, Se, Co, and Au among sulfide minerals in this deposit. Except molybdenite, which host high concentrations of Te and Se, pyrite and chalcopyrite generally have higher Te contents than bornite and sphalerite, whereas bornite and chalcopyrite exhibited relatively high Se concentrations. Cobalt and Au are dominantly hosted in the pyrite and chalcopyrite, respectively, although the highest Au concentration up to 14 ppm was analyzed in pyrite. Principal component analysis of trace element contents and time-resolved LA-ICP-MS signal depth profiles indicate that Te occurred as Te-Ag minerals and mineral inclusions within the sulfides, whereas Se and Co are incorporated into the lattices of sulfide minerals. Principal component analysis of trace element contents in various sulfides exhibit intimate Pb-Bi-(Cu)-Au associations, suggesting that Au is present as tiny mineral inclusions coexisting with either Cu-Bi sulfosalts or Pb sulfides or sulfosalts. This case study also highlights that Te and Se hosted in pyrite are not recoverable with current recycling technologies.

Occurrence characteristics and factors that influence shale oil in the Jurassic Lianggaoshan Formation, northeastern Sichuan Basin

Well Ping'an 1, located in the northeastern Sichuan Basin, tested 112.8 m3/d of oil from the Lianggaoshan Formation, marking an important breakthrough in shale oil production. However, due to the influence of complex lithofacies, high thermal maturity, and limited exploration, the occurrence and factors that influence shale oil across the different lithofacies of the Lianggaoshan Formation remain unclear, thereby severely impeding exploration and development. This study systematically examines the occurrence and factors that influence shale oil (adsorbed oil and free oil) in the Lianggaoshan Formation through an integrated approach involving petrology, geochemistry, scanning electron microscopy, nuclear magnetic resonance spectroscopy, multi-temperature pyrolysis, and gas chromatography. Results demonstrate the following: (1) Residual shale oil (adsorbed oil) in the study area predominantly exists as oil films, precipitated oil, and residues (asphalt). Oil films appear on the edges of organic matter (OM), clay minerals, pyrite, and felsic minerals. Crude oil adheres as thin layers to mineral edges, with part of the oil resulting from the lipophilic properties of OM. Precipitated oil tends to accumulate around organic pores, and at higher maturity stages, heavy oil components adhere to mineral surfaces as residues. The hydrocarbon loss of the sample is serious, and free oil is difficult to observe due to experimental processing. (2) Based on the experimental results of preserved cored samples, the shale oil in the study area is mainly free oil (0.86–4.46 mg/g, average 1.99 mg/g), followed by adsorbed oil (0.0007–1.36 mg/g, average 0.43 mg/g). The presence of higher concentrations of clay minerals and total organic carbon (TOC) correlates with increased quantities of free and adsorbed oil in the Lianggaoshan Formation. (3) The two-dimensional nuclear magnetic resonance method combined with the “e” index method was employed to quantify the free oil volumes in shale reservoirs of varying maturity within the study area. The recovery coefficient initially increases rapidly and then gradually with increasing Ro (vitrinite reflectance) values. Compared with other lithofacies types, OM-rich laminated argillaceous shale and OM-poor laminated siliceous shale have higher free oil content, which makes them easier to produce, in other words, these two lithofacies should be preferred as favorable exploration and development targets.

Genesis of the Mamuniyeh copper deposit in the central Urumieh-Dokhtar Magmatic Arc, Iran: Constraints from geology, geochemistry, fluid inclusions, and H–O–S isotopes

The Mamuniyeh Cu deposit is located in the central part of the Urumieh-Dokhtar Magmatic Arc (UDMA), 10 km south of the city of Mamuniyeh, Iran. Mineralization is controlled by faults with a NW-SE trend and hosted within an Eocene volcanic sequence and Oligo-Miocene hypabyssal calc-alkaline monzonitic and gabbroic bodies. Quartz + chalcopyrite veins are most abundant and high-grade ore containing up to 5 wt% Cu, although quartz + pyrite veins have the most abundant sulphide content. In addition, quartz + chalcopyrite + specular hematite ± pyrite veins/veinlets are another common mineralized assemblage in the Mamuniyeh copper deposit, with pyrite, chalcopyrite, bornite, and oxide minerals (specular hematite, titanomagnetite, and magnetite) typical of the hypogene stage. Chalcocite, covellite, and dignite also formed at the margins of primary sulphides in the supergene (paleoweathering) stage. The mineralized veins exhibit colloform, crustiform, open space-fillings, replacements, and dissemination textural characteristics associated with mineralizing assemblages with silicification, argillization, chloritization, and sericitization assemblages. The salinity for L > V fluid inclusions is between 1.74 to 11.7 wt% NaCl and for (V > L) inclusions between 1.7 to 11.4 wt% NaCl. The average homogenization temperature and salinity for quartz + chalcopyrite + pyrite veins is 186 °C and 4.9 wt% NaCl. In the quartz + chalcopyrite assemblage an average of 185 °C and 4.5 wt% NaCl and for quartz + chalcopyrite + specularite ± pyrite (QCSP) an average of 195 °C and 5.59 wt% NaCl was determined. In these three vein types, the fluid density has almost identical values ranging from 0.8 to 1.0 g/cm3. The mineralizing system evolved in two-stages; the first metal precipitation occurred at less than 1 km of crustal depths and second metal deposition stage at shallower crustal levels (less than 500 m). Although it appears that the boiling process occurred within the fluids of the area, the primary factor contributing to Cu mineralization was influenced by fluidmixing processes. The δ18O and δD values of ore fluids computed vary from + 6.08 to −0.50 ‰ and −92 to −71 ‰, respectively, indicative of the blending of oxidizing and cooler meteoric waters with primary magmatic fluids. Calculated values of δ34S of H2S in equilibrium with chalcopyrite ranges from −7.6 to −1.9 ‰ and H2S in equilibrium with pyrite ranges from −7.1 to −3.8 ‰, respectively; this is consistent with monzodiorite to gabbro as the magmatic sulphur source for copper mineralizing fluids. Furthermore, the QCSP vein data align more closely with primary magmatic water compared to other veins, suggesting that precipitation occurred mainly from magmatic fluids, which experienced depletion in δ18O due to mixing with meteoric waters (shallow oxygenated ground waters), which caused sulphide deposition. The geochemical features for these magmas show that contamination with crustal materials occurred during the ascent of the parent magma, as well as the role of suprasubduction fluids released from the subducting plate in mantle metasomatism. Based on all evidence, Cu mineralization in the Mamuniyeh deposit has been categorized as a low-sulphidation epithermal-type system, which formed during active magmatism in the central part of UDMA.

Genesis of Xinjiazui Gold Deposit: In Situ Geochemical Constraints from Arsenopyrite

The Xinjiazui gold deposit marks a notable significance in prospecting within the Back-Longmenshan tectonic belt, located on the northwest margin of the Yangtze Block, China. Despite the extensive studies conducted on this deposit, the source of the ore-forming materials remains unclear, leading to ongoing debates regarding the genesis of this deposit. This study analyzed in situ (EPMA and LA-ICP-MS) trace elements and S-Pb isotopes of arsenopyrite, solely from the principal metallogenic stage and paragenetic with native gold. The results show that the gold in arsenopyrite occurs as invisible gold (Au3+), with an average concentration of 9.38 ppm, whereas the concentrations of magma-related elements, such as W, Sn, Mo, and Bi, are very low. The sulfur isotopes (34S) of arsenopyrite range from 8.32‰ to 10.16‰, aligning closely with the deep metamorphic basement (Pt3l). Meanwhile, the lead isotopes in arsenopyrite display characteristics typical of those found in orogenic belts. A comprehensive analysis of the abundance of gold indicated that the metallogenic materials (sulfur and gold) primarily originated from Pt3l. Additionally, the arsenopyrite thermobarometer indicated that the Xinjiazui gold deposit formed in a medium–low-temperature, medium metallogenic environment (5.57–8.69 km), with a sulfur fugacity (log f (S2)) below −8.4. Combined with previous research results, this study proposes that the Xinjiazui gold deposit is a subduction-related mesozonal orogenic gold deposit. In gold prospecting and exploration in the Back-Longmenshan tectonic belt, it is essential to focus on the distribution of brittle-ductile shear zones and location of the quartz veins associated with pyrite and arsenopyrite mineralization.

Distribution and enrichment processes of cobalt in the Longqiao iron skarn deposit in Eastern China

Longqiao is a cobalt-rich skarn iron deposit in Eastern China. As a typical representative of its type, it provides an opportunity to study the occurrence, distribution, and factors controlling cobalt in these deposits. Cobalt-bearing ores in Longqiao deposit can be classified into two types: cobalt-bearing diopside-magnetite ore (Co-Di-Mag) and cobalt-bearing phlogopite-magnetite ore (Co-Phl-Mag). Systematic whole-rock geochemical analysis, automated mineral analysis (TESCAN Integrated Mineral Analyzer, TIMA), and LA-ICP-MS trace element analysis were conducted on the two ore types. Three independent cobalt minerals（cobaltite, glaucodot, and carrollite）were found in Co-Di-Mag; no independent cobalt minerals were found in Co-Phl-Mag. TIMA and LA-ICP-MS analyses showed that cobalt in Co-Phl-Mag is mainly hosted in pyrite, so the pyrite content has a decisive role in the overall cobalt content. Cobalt in Co-Di-Mag is controlled by the content of magnetite, pyrite, and cobalt minerals.In both the diopside-magnetite stage (Stage I) and phlogopite-magnetite stage (Stage II), the cobalt mainly occurs in magnetite, and its content gradually decreases from 80 to 30 ppm as the system evolved. During the sulfide stage, minor pyrite deposited near the intrusion, and cobalt occurs in the pyrite lattice and also forms numerous independent cobalt minerals. Pyrite is abundant in the distal part of the ore-body, where all cobalt occurs in pyrite, and independent cobalt minerals are absent.Cobalt mainly occurs in pyrite in Longqiao deposit, which is favorable for beneficiation and recovery. Similar skarn iron deposits are widespread in eastern China, and the cobalt in these deposits has potential for recovery.

Fluid evolution and genesis of the Shipenggou gold deposit in Central Jilin Province, China: Constraints from C–H–O and in–situ sulphur isotopes of pyrite and fluid inclusions

The origin and evolution of the Shipenggou gold deposit in the Shipenggou–Jiapigou–Jinchengdong (SJJ) gold belt in Jilin Province, Northeast China, remain poorly understood. In this study, fluid inclusion and C–H–O–S isotopes from the Shipenggou deposit were investigated to clarify the fluid evolution and mineralisation process. The gold mineralisation is hosted in the biotite plagiogneiss of the Archaean Sandaogou Formation and is dominated by gold–bearing quartz veins. The orebodies are controlled by NNE– and NEE–striking brittle–ductile structures. Four stages of mineralisation have been identified: (I) milky quartz–minor pyrite, (II) quartz–pyrite–minor gold, (III) gold–quartz–polymetallic sulphide, and (IV) quartz–carbonate. Fluid inclusions were identified as four types: aqueous (VL–type), CO2–bearing (CL–type), CO2–rich (LC–type), and carbonic (PC–type). VL–, CL–, LC–, and PC–type FIs were developed within quartz from Stages I–II. Stage III quartz contains both CL– and VL–type FIs. Only VL–type FIs were observed in calcite from Stage IV. The total homogenisation temperatures (Tht) of FIs in Stages I, II, III, and IV are of 281.5–324.8, 215.5–269.1, 151.2–198.3, and 125.4–149.5 °C with salinities of 2.8–13.2, 2.8–9.6, 3.2–8.4, and 3.0–5.9 wt% NaCl eqv. Laser Raman spectroscopy analysis indicated the CL– and PC–type FIs from Stages I and II contain CO2 and minor quantities of CH4. The ore–forming fluids have developed from a medium temperature, low–medium salinity immiscible NaCl–H2O–CO2 ± CH4 system to a low temperature, low salinity homogeneous NaCl–H2O system. The HO isotopic compositions indicate that the initial ore–forming fluids were mantle–derived magmatic water. Subsequently, the ore–forming fluids were gradually joined by meteoric water. δ13C values indicate C in the fluids have originated from organic matter. Organic matter may have originated from the mantle, which mixed crust materials influenced by the subduction of the Palaeo–Pacific slab. In–situ, S isotope data of pyrite indicate that the origin of sulphur at the Shipenggou deposit is the mantle containing a crust component. Based on the above analysis results, the Shipenggou gold deposit is a mesothermal magma-hydrothermal vein–type gold deposit.

An investigation on pyrite floatability using stable micro-nanobubble-assisted flotation

This study critically examines the impact of micro-nanobubble (MNB)-assisted flotation on pyrite recovery in bulk ore, and clarifies the intricate relationship between pyrite and its associated ore. The physicochemical properties of MNBs and the interaction mechanisms between xanthate collector and pure pyrite mineral were evaluated using advanced analytical techniques, including Dynamic Light Scattering (DLS), Field-Emission Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy (FESEM-EDX), and Ultraviolet-Visible Spectroscopy (UV-Vis), in the absence and the presence of MNBs. MNBs were created through hydrodynamic cavitation, and their characteristics revealed a size increase from 600 nm to 3 µm over 25 days. Notably, the zeta potential measurements indicated an increase from -2.5 to 0 mV at a constant pH of 8, correlating with the geometric mean size of MNBs coarsening from 600 nm to 2-3 µm. The FESEM and EDS analyses disclosed that ultrasonic treatment effectively dispersed ultrafine surface coatings on pyrite particles, increasing iron and sulfur purity by 8% and 6%, respectively, and significantly reducing surface oxygen by 53%. Micro-flotation and batch rougher kinetic flotation experiments were conducted with and without MNBs, leading to a 7% and 8% improvement in recovery for pyrite mono-minerals (-105+53 µm) and its ore (d<sub>80</sub>=150 µm), respectively. The sorption behavior of sodium isopropyl xanthate (SIPX) collector on the particle surface was also investigated at various concentrations (ca. 10-160 µM) in the presence and absence of stable MNBs and demonstrated that the presence of MNBs resulted in a 1.6-fold increase in collector absorption on the pyrite surface, confirming the findings obtained from micro-flotation. Moreover, adsorption behavior is up to 1.3 times compared to the scenario without MNBs. The adsorption process was controlled by a pseudo-second-order model, indicating a chemical sorption mechanism.

Shale Oil Generation Conditions and Exploration Prospects of the Cretaceous Nenjiang Formation in the Changling Depression, Songliao Basin, China

Low-maturity shale oil predominates in shale oil resources. China’s onshore shale oil, particularly the Cretaceous Nenjiang Formation in the Songliao Basin, holds significant potential for low-maturity shale oil, presenting promising exploration and development prospects. This study delves into the hydrocarbon generation conditions, reservoir characteristics, and oil-bearing property analysis of the mud shale from the Nen-1 and Nen-2 sub-formations of the Nenjiang Formation to pinpoint favorable intervals for shale oil exploration. Through the integration of lithology, pressure, and fracture distribution data in the study area, favorable zones were delineated. The Nen-1 sub-formation is widely distributed in the Changling Depression, with mud shale thickness ranging from 30 to 100 m and a total organic content exceeding 2.0%. Type I kerogen predominated as the source rock, while some samples contained type II kerogen. Organic microcomponents primarily comprised algal bodies, with vitrinite reflectance (Ro) ranging from 0.5% to 0.8%. Compared to Nen-1 shale, Nen-2 shale exhibited less total organic content, kerogen type, and thermal evolution degree, albeit both are conducive to low-maturity shale oil generation. The Nen-1 and Nen-2 sub-formations predominantly consist of clay, quartz, feldspar, calcite, and pyrite minerals, with minor dolomite, siderite, and anhydrite. Hydrocarbons primarily reside in microfractures and micropores, including interlayer micropores, organic matter micropores, intra-cuticle micropores, and intercrystalline microporosity, with interlayer and intra-cuticle micropores being dominant. The free oil content (S1) in Nen-1 shale ranged from 0.01 mg/g to 5.04 mg/g (average: 1.13 mg/g), while in Nen-2 shale, it ranged from 0.01 mg/g to 3.28 mg/g (average: 0.75 mg/g). The Nen-1 and Nen-2 sub-formations are identified as potential intervals for shale oil exploration. Considering total organic content, oil saturation, vitrinite reflectance, and shale formation thickness in the study area, the favorable zone for low-maturity shale oil generation is primarily situated in the Heidimiao Sub-Depression and its vicinity. The Nen-2 shale-oil-enriched zone is concentrated in the northwest part of the Heidimiao Sub-Depression, while the Nen-1 shale-oil-enriched zone lies in the northeast part.

Advanced smectite alteration and the role of accessory reactants at 180 °C: New experimental constraints on the stability of bentonite

Bentonite clay is commonly accepted as an appropriate material for backfilling the space between the radioactive canisters and the host rock of planned underground repository sites for waste disposal. Despite its favourable properties as a hydrodynamic seal, its long-term stability remains a concern. This experimental study of a Bavarian bentonite investigated advanced montmorillonite (smectite) illitisation at 180 °C in the presence of K-oxalate and/or the accessory minerals of pyrite and calcite. The formation of mixed-layered illite-smectite was quantified by X-ray diffraction Rietveld refinement and the crystal chemistry was determined by transmission electron microscopy. The results showed neocrystallisation of a celadonitic illite-smectite (up to 63% illite-layers) after treatment with KCl or K-oxalate with increased Al3+ in the tetrahedral sheets, reduced amounts in the octahedral locations and increased fixation of non-exchangeable K+ ions in response to the increased layer charges. K-oxalate complexation of Al3+ and enhanced dissolution of the smectite resulted in the formation of a possible intermediate amorphous phase and illite-smectite crystallites with additional vacant sites explaining the lower number of octahedral ions (<2 per formula unit). Adding 10% pyrite, 10% calcite, or 5% of each, did influence the degree of alteration to a recognisable degree in the presence of KCl, but the effects on the rate of illitisation were minimal when reacted with K-oxalate, which further increased illitisation by up to 6.4 times. Although batch reactor experiments do have limitations compared to complex repository conditions, our results do indicate that claystone host rocks low in organic matter should be favoured over organic-rich lithologies that are likely to contain oxalate ligands or similar catalysing compounds.

Elemental Geochemistry and Pb Isotopic Compositions of the Thick No. 7 Coal Seam in the Datun Mining Area, China

Thick coal seams recorded abundant petrological, geochemical, and mineralogical information regarding their formation, which in turn can reflect the characteristics of the coal-forming environments, provenance attributes, paleoclimate, and so on. In order to explore the geochemical and lead isotope characteristics of thick coal seams, the No. 7 coal seam in the Datun mining area, Jiangsu Province of China, was selected as the research object. In this work, 29 samples (including coal, roof, and floor rock samples) were collected from three coal mines in the Datun mining area. Through an analysis of the mineral composition and element geochemical characteristics in the coal samples, the enrichment degree of trace elements and modes of rare earth elements were determined. The genetic mechanism of abnormal enrichment of enriched elements is discussed, especially the modes of occurrence and isotope characteristics of Pb. The results showed the following: (1) The main minerals in the coal samples include quartz, potassium feldspar, plagioclase, calcite, dolomite, pyrite, gypsum, and clay minerals, with clay minerals, calcite, quartz, and dolomite being the most common. (2) The major element oxides in coal mainly include SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, TiO2, P2O5, and FeO. In the vertical direction, the variation of SiO2, Al2O3, Fe2O3, MgO, K2O, and FeO in coal samples from the three coal mines is consistent. The average value of Al2O3/TiO2 in the samples of Kongzhuang, Longdong, and Yaoqiao coal mines is 28.09–50.52, which basically locates the samples in the felsic source area, such that the sediment source is considered to be felsic source rock. (3) Elements U, La, Pb, and other elements are more enriched in Kongzhuang coal mine samples; elements Th, U, La, Pb, and other elements are more enriched in the Longdong coal mine samples; and elements Th, U, La, Pb, and other elements are more enriched in the Yaoqiao coal mine samples. Furthermore, W is enriched in Yaoqiao mine samples and is highly enriched in Longdong mine samples. The mining area is generally rich in the elements U, La, and Pb. The distribution curves of rare earth elements in the three mines are inclined to the right, with negative Eu anomalies. The enrichment is of the light rare earth enrichment type. (4) Pb isotope data show that the samples from the three mines are mainly distributed in the orogenic belt and the subduction zone lead source areas, where the upper crust and the mantle are mixed, with individual sample points distributed in the mantle and upper crust lead source areas.

Evolution of pore structure and diagenetic stages of late Permian shales in the Lower Yangtze Region, South China

This study examines the evolution characteristics of shale pores in the Late Permian Longtan Formation located in the Lower Yangtze region of South China. The complete process of thermal evolution of the samples was achieved through thermal simulation experiments while identifying qualitatively the pore types and their development characteristics using field emission-scanning electron microscope (FE-SEM). Quantitative analysis of pore size distribution was conducted through mercury intrusion capillary pressure (MICP), nitrogen (N2) and carbon dioxide (CO2) adsorption experiments. The paper comprehensively analyzed the pore evolution characteristics and controlling factors of shale in the study area, with an analysis of diagenetic differences. Findings reveal that during the pore evolution process, both morphology and pore size are influenced by thermal maturity. The pore volume is dominated by mesopores and macropores, while the specific surface area is mainly dominated by mesopores and micropores. Thermal evolution promotes the formation of micropores and mesopores but hinders the development of macropores. Moreover, clay minerals transformation and mineral dissolution make certain contributions to the development of micropores. The diagenesis in the study area is controlled primarily by the pyrolysis of organic matter. Pyrite and clay minerals are the first to dissolve, followed by calcite and quartz. Five stages of evolution characterization have been identified from low-mature stage (Ro = 0.88 %) to overmature stage (Ro = 3.35 %) in combination with diagenesis. The development of pore structure and its influencing factors vary across different stages. The influencing factors mainly include hydrocarbon generation from organic matter, compaction, mineral transformation, and dissolution. The process of hydrocarbon generation in organic matter occurs throughout the entire pore evolution process, resulting in the development of numerous micropores and mesopores. Compaction primarily impacts pore development during the early diagenetic stage, causing a substantial transition of primary mineral pores from macropores to mesopores. Mineral transformation and dissolution take place during and after the middle diagenetic stage. The former governs the development of mesopore-sized clay interlayer pores, while the latter primarily generates micropores.

The rise of biogenic silicon cycling and microbial silicification promoted Mesoproterozoic chert deposition

The silicon (Si) cycle is intimately interlinked with other biogeochemical cycles (e.g., carbon and nitrogen) and plays an important role in regulating long-term global climate change and biotic evolution in Earth's history. The abundance of cherts in Mesoproterozoic shallow-marine carbonates implies unique environmental conditions for silica precipitation, but the driving mechanism behind the Si cycle in Mesoproterozoic oceans remains unclear. In this paper, we report an integrated study of the cherts from the ∼1.48 Ga Wumishan Formation of North China. The Wumishan cherts predominantly consist of microquartz (∼90%), with some silica-replaced carbonate (∼5%) and minor pyrite (∼1%) grains, indicating that the cherts were largely formed through primary silica precipitation. High germanium/silicon molar ratios (Ge/Si = 0.71–19.1 μmol/mol; mean = 8.83) and positive europium anomalies (Eu/Eu* = 0.41–2.42; mean = 1.41) of the cherts suggest a considerable contribution from hydrothermally derived Si. Diverse microbial components, including organic-rich filaments, EPS (extracellular polymeric substances) relics, mat fragments and picocyanobacteria fossils, are observed in the Wumishan cherts. These components, together with abundant organominerals resulted from the interactions of microbes and dSi in ambient environments, imply that microbial activities played critical roles in silica deposition. The Si liberated from degraded EPS or EPS-Si complex may have locally increased the dSi concentrations and changed chemical conditions in the substrate and pore-waters, promoting silica precipitation. Given that picocyanobacteria and some other prokaryotes can accumulate significant amounts of silica in their cells and EPS, biogenic silica from decomposed microbial biomass may have exerted an important influence on silica precipitation in shallow-marine environments of the Mesoproterozoic ocean.

COMPARATIVE ANALYSIS OF FLOTATION EFFICIENCIES BETWEEN MICROFLOTATION CELL AND BATCH FLOTATION CELL TESTS

One of the most important methods in the beneficiation of sulfide ores is flotation. Flotation experiments on a laboratory scale are mainly carried out through batch flotation and microflotation tests. In this study, comparative flotation experiments of pyrite minerals were conducted under the same conditions using the two methods mentioned above. A series of experiments were carried out with different pH values and collector dosages selected as flotation parameters. The highest flotation recovery was obtained at a pH of 7.5 with the use of PAX. Furthermore, within the conditions studied, a correlation of 94% was found between the two flotation techniques when using PAX, while it was 98% in the use of PEX. In this study. It was shown that the microflotation method can be used to estimate the efficiency values that can be obtained with batch flotation experiments.

Enhanced classification of pyrite generations based on mineral chemistry using uniform manifold approximation and projection (UMAP)

Trace element signatures are tracked to unravel the genetic history of ore deposits in several mineral systems. This is particularly true for pyrite, a ubiquitous component of many ore-forming systems, including orogenic gold deposits. Here, we critically compare the efficacy of utilizing Uniform Manifold Approximation and Projection (UMAP) versus Principal Component Analysis (PCA) as dimensionality reduction tools applied to a 31 element dataset collected using Laser Ablation Inductively Coupled Mass Spectrometry of pyrite grains from the Kibali gold district (Democratic Republic of Congo). Because of the non-linearity inherent to mineral chemistry and because of its superior preservation of local (distances within clusters) and global (separation between clusters) data relationships, the UMAP approach outperforms dimensionality reduction by PCA. We further present a workflow in which UMAP dimensionality reduction is followed by k-means clustering to guide the classification of pyrite generations in the Kibali case study. Validating this approach with trace elements and UMAP + k-means on a seed-by-seed petrography basis shows that the workflow significantly enhances the original pyrite classification, previously based on texture. This study thus emphasizes the utility of employing advanced statistical analysis methods to capture the intricate nature of pyrite formation. These findings will shape best practices for handling large multi-element datasets in pyrite mineral chemistry studies and are extrapolatable to other mineral systems in which trace element signatures are used to infer the conditions of ore deposit genesis.

Enhanced nitrogen and phosphorus removal by iron-manganese mediated autotrophic denitrification in electrochemical system and the underlying mechanisms

At present, the research on Fe/Mn autotrophic denitrification is very limited, and the underlying mechanism in electrochemical system is not clear. In this study, an electrochemical system based on Fe-Mn autotrophic denitrification was constructed for the treatment of low C/N wastewater. The underlying mechanism and electrochemical process of Fe/Mn-mediated autotrophic denitrification were elucidated. The results showed that pyrite and manganese mineral matrix had no significant effect on COD removal, but had significant effect on nitrogen removal. R1 (activated carbon matrix) had the lowest nitrogen removal rate, with an average of 66.06 %. The mean removal rate of R2 (iron matrix) and R3 (manganese matrix) were 93.94 % and 95.89 %, respectively. The coupling of iron/manganese ammoxidation and autotrophic denitrification was the main mechanism to achieve efficient nitrogen removal. ICP and FIRT results showed that strong REDOX reactions of Fe, Mn and sulfur occurred at the anode of MFC. Direct precipitation of iron and manganese and electrochemical flocculation (FeOOH) effectively improved phosphorus removal. The phosphorus removal rates of R2 and R3 reached 93.89 % and 95.85 %, respectively. R3 has high electron transfer efficiency with a maximum voltage of 680 mV. Metagenomic analysis showed that 19 important transcripts associated with nitrogen metabolism pathways and 4 nitrogen metabolism pathways were detected. Enzymes encoded by nap A and nar G genes were abundant in R3 system. Reductase encoded by nrfA and nrfH genes was abundant in R2 system. Iron REDOX genes iroE, iroN, oorA, and manganese REDOX genes moxR, moxA were detected. The results of metabolic pathways and related enzymes further revealed the coupling cycle relationship between metal elements and nitrogen, phosphorus and sulfur in electrochemical systems. This study can not only provide a new method for efficient nitrogen and phosphorus removal of sewage, but also provide scientific basis for improving the geochemical cycle of metal elements and nitrogen elements.

MINERALOGICAL AND GEOCHEMICAL PARAMETERS OF SNOW COVER WITHIN THE ANTHROPOGENICALLY DISTURBED SITES OF THE NADYM-PUR INTERFLUVE (NORTHERN PART OF WESTERN SIBERIA)

The article analyzes the content of metals in solid aerosols and snow water sampled in the anthropogeni-cally disturbed and background sites of the Nadym-Pur interfluve. The results of microscopic studies of solid aerosols showed the presence of secondary minerals, technogenic formations, as well as a large amount of pyrite in samples from the eastern part of the study area. The maximum concentrations of metals in solid aero-sols were found in snow of the sanitary protection zones of waste disposal facilities, with the exception of Ca, which prevails in snow cover of Novy Urengoy (up to 10% of dry matter). The urbanized area is characterized by the highest values of dust load (up to 111 mg/m2 a day). The local contamination with Ba within the waste landfills in Novy Urengoy is associated with the sites of barite and drilling waste processing. We applied the factor analysis to identify the main metal associations characteristic of solid aerosols from different functional zones: Ca-Co-V-Mn (city), Ba-Sr-K-Na and Cd-Cu-Pb (waste disposal sites), Cu-Ni-Cd (the entire studied area). Based on the study of the content of dissolved forms in snow water, a high mobility of metals in the northern landscapes and its decrease in urban environment were revealed. The mineralogical and geochemical analysis of snow suggests the influence of the Norilsk industrial region on the eastern part of the Nadym-Pur interfluve, Zn, Cu, Ni, Pb and the mineral pyrite being the indicators. The risks of environmental pollution under the aerotechnogenic transport are associated with high content of Zn, Cu, Ni, Pb and Ba in solid aero-sols. The calculation of the Toxicity Probability Index (MERMQ) showed that some aerosol samples from the landfill sites have a high probability of biological effects. Using data on the chemical composition of soils and soil water, no visible effect of snow pollution on the growth of metal concentrations in soil and soil water was revealed, with the exception of local contamination with Ba, which led to a twofold increase in the content of the metal in the upper soil horizon.

The Ciclón - Exploradora epithermal polymetallic ore deposit: An Eocene Cordilleran-type of mineralization in the Domeyko Cordillera, Northern Chile

The Ciclón-Exploradora Project is located in the Exploradora Porphyry Copper District, which corresponds to an old artisanal mining and exploration area 65 km northeast from El Salvador Copper Mine, between 3200 and 4000 m.a.s.l. and inserted within the Eocene-Oligocene metallogenic porphyry belt and Domeyko Cordillera. Exploitation has been discontinuous since the late mid-19th century. It first started with production at the Copper Exploradora Mine, and later for Au–Ag at the Ciclón and San Carlos mines. Nevertheless, after decades of work and exploration the district has great potential for new discoveries.Epithermal polymetallic (Cu–Ag–Zn–Pb–Au) mineralization took place related to the evolution of the Exploradora Plutonic and Porphyry Complex. This Eocene Complex is a composite of dioritic to monzodioritic magmatic intrusions including several intermediate composition Cu–Au and Cu–Mo porphyry centers, mostly emplaced in NNE to NE-oriented corridors. The hosted rocks consists of folded Triassic and Jurassic calcareous sedimentary units partially altered by a kilometric metasomatic envelope that contains skarn mineralization.The complex was mainly emplaced syntectonically along the Sierra Castillo Fault System, which is part of the margin-parallel Domeyko Fault System. These faults together with NE and NW striking transversal faults were active during the Eocene, playing a key role in the emplacement of magmatism and mineralization at the district.The main magmatic phases of the Exploradora Complex record different levels of alteration exposure, mineralization and geochronological ages suggest at least three discrete and continuous episodes of magmatism during ∼4 m.y. (1) An early composite of dioritic to monzodioritic intrusions (38-36 Ma), generally associated with coarse Ca (K) alteration and spatially close to Zn or Fe exoskarn mineralization. (2) An early to inter mineral hypabyssal rocks (36-35 Ma) composed of dacitic to rhyolitic porphyries and aplitic rocks, mostly affected by k-feldspar, propylitic, quartz and argillic alteration, locally with secondary biotite and Cu anomalies. Include quartz monzodiorite porphyries exposing Cu–Au mineralization associated with potassic alteration (biotite-magnetite plus albite) and related quartz-veinlets. (3) CODELCO's Exploradora Cu–Mo mineralization (35-34 Ma) associated with late dacitic and dioritic porphyries, HS-Au mineralization veinlets and a post-mineral diatreme.Polymetallic mineralization occurs at the western part of the district, hosted mainly in sedimentary and intrusive rocks and partially at major intrusion contacts. The Ciclón-Exploradora polymetallic deposit is a 5 km-long NS- and NNW-striking vein-breccia-fault, with mainly sinistral movements, it includes carbonate replacement deposits and dissolution breccia bodies nearby.The tectonic stress field orientation related to the vein-breccia-fault mineralization records subhorizontal NW-trending σ1, SW-trending σ3, and subvertical σ2. Polymetallic hypogene mineralization shows a consistent evolution from low sulfidation conditions to intermediate sulfidation assemblages, spatially related to an early skarn stage characterized by the presence of magnetite, pyrrhotite, Fe-rich sphalerite, developed in calcareous sedimentary rocks. Skarn zonation includes garnet-pyroxene-wollastonite-scapolite minerals. Epithermal polymetallic mineralization shows four main stages. The first and second stages consist of pervasive chlorite followed by chlorite-pyrite veinlets that may or may not contain quartz, and massive pyrite mineralization bodies generally forming euhedral crystals. The second phase ends with a Cu-dominant stage given by chalcopyrite-quartz (±chlorite - sericite – pyrite) and lower contents of Ag-bearing sulfosalts. The third stage is recognized as a polymetallic event characterized by multiple veinlets emplaced both in intrusive and sedimentary rocks where it also forms replacement ore bodies along lithological contacts. It consists of Cd-rich sphalerite, galena, Fe–Mn–Zn carbonates, and minor amounts of chalcopyrite, tennantite-tetrahedrite, and other Ag sulfosalt minerals. Gold is present as native and spectrum minerals with quartz. Main alteration minerals are quartz-kaolinite and minor amounts of sericite. The last stage consists of calcite ± arsenopyrite veinlets crosscutting the previous mineralization. This paragenetic evolution is similar to the one observed in several epithermal porphyry-related polymetallic “Cordilleran” deposits (e.g., Cerro de Pasco, Perú).Crosscutting relationship and exposure of epithermal mineralization, porphyry alteration and magmatism suggests that, in a short period (38–34 Ma), the whole district was exhumed probably several kilometers (3–6 km), related to a compressional to transpressional deformation regime.

Gold mineralization in the diaphthorites of the Verkhne-Timptonskiy ore district (Aldan-Stanovoy shield)

In the Verkhne-Timptonskiy gold ore district, located where the Stanovoy and Aldan blocks intersect (Aldan-Stanovoy shield), substantial placer gold deposits have been found in the Gonam, Timpton, and Iengra rivers. The exploration of certain deposits in this area began at the end of the 19th century. Despite exploration efforts conducted in the second half of the 20th century, only minor gold ore findings were made, with uncertain links to greenstones and igneous formations from various periods. After conducting a thorough analysis of both existing and new data on the geology and metallogeny of the Verkhne-Timptonskiy gold ore district, we have concluded that gold occurrences in diaphthorites of the Kholodnikan belt display characteristic features of orogenic-type gold deposits. These features include disseminated pyrite and veinlet mineralization containing iron (Fe), lead (Pb), zinc (Zn), copper (Cu) sulfides, and sulfosalts. The near-ore alterations are represented by silicification, sericitization, carbonatization, and beresitization, characteristic of mesothermal fluid systems. Moreover, we identified common features of the geological structure and metallogeny of the Verkhne-Timptonskiy gold ore district and the Jiaodong province of the North China Craton. Thus, gold mineralization in the Verkhne-Timptonskiy gold ore district and the Jiaodong province is spatially associated with suture zones. In the Verkhne-Timptonskiy gold ore district, the Amga zone of tectonic melange in the Paleoproterozoic era was one of the regions where cratonization of blocks of the Earth’s crust occurred. Later, it became a zone of permeability and concentration of tectonothermal and metallogenic events of various ages. The results obtained will help assess the metallogenic potential of the Verkhne-Timptonskiy district and the Aldan-Stanovoy shield as a whole. They make it possible to increase the efficiency of search operations and focus on localizing research objects.

Uranium enrichment driven by paleomarine condition and event deposition: Insights from the lower Cambrian Niutitang Formation organic-rich shales in northeastern Guizhou, South China

Organic-rich shale related uranium (U) mineralization has attracted widespread attention as a strategic and clean alternative to fossil energy and a paleoceanic redox proxy. A comprehensive study of mineralogy, organic geochemistry and elemental geochemistry of the lower Cambrian Niutitang Formation organic-rich shales in northeastern Guizhou, South China was conducted to address this issue. SEM-EDS results showed that the U occurrence state in the Niutitang Formation shales is dominated by nanoscale U minerals, mainly including coffinite, brannerite, U-bearing apatite and U-bearing xenotime. Various states of U are closely associated with organic matter, apatite, pyrite and clay minerals. Based on geochemical indexes, paleomarine condition and event deposition jointly drove the U enrichment in the Niutitang shales, in which hydrothermal activities and/or volcanic eruptions increased U fluxes in seawater and euxinic environment with high primary productivity provided a favorable condition for U reduction. The adsorption, complexation and reduction of UO22+ by organic matter and the formation of uranyl phosphate complexes by the combination of phosphate and UO22+ accelerated U immobilization and enrichment from bottom water to sediments. The microbial activities (e.g., BSR) in this process created favorable euxinic conditions and released inorganic-phase P to provide available ligands for UO22+. The U enrichment models of the lower Cambrian Niutitang shales in northeastern Guizhou were established. This paper provides a new insight into the U enrichment mechanism in organic-rich shales, and may also have implications for the applicability of U as redox proxy and the exploration of organic-rich shale related U deposits.