Pyrite Minerals Research Articles

Pyritic mineralization halo above the Tara Deep Zn-Pb deposit, Navan, Ireland: Evidence for sub-seafloor exhalative hydrothermal processes?

The Tara Deep Zn-Pb deposit, at Navan, Ireland, includes sub-economic pyrite-rich mineralization extending laterally for about 2 × 2 km within the overlying Lower Viséan calc-turbidites, known as the ‘New-Thin Bedded Unit’. Here, we investigate the genesis of this pyritic mineralization and its links to the limestone-hosted Zn-Pb deposit lying 100 m below it.Four mineral assemblages have been identified: 1) in black shales, laminated pyrite comprises thin framboid-rich layers with minor interstitial sphalerite, both showing variable but low δ34S values ranging from −37.4 to 3.3‰; 2) in calcarenite and calcsiltite layers, pyritized fossils are widely distributed and occur chiefly as biodebris replaced by low δ34S pyrite (mean values of −13.2‰); 3) a replacive assemblage occurs as late remobilizations exhibiting both crosscutting and bedding-parallel styles, overprinting the early laminated pyrite. It comprises mostly of marcasite, with minor pyrite, sphalerite, chalcopyrite, galena, stibnite and Co-pentlandite, with high δ34S values up to 24.5‰; and 4) in black shales, bedded sulfide-rich cherts comprising microcrystalline quartz lenses exhibit δ18O mean values of 25.3‰. Cherts are rimmed by dolomite, associated with marcasite, pyrite, sphalerite, chalcopyrite, galena, siegenite and stibnite also with high δ34S values up to 44.2‰. In general terms, pyrite shows a relatively high Co/Ni ratio > 1 and sphalerite Zn/Cd ratios vary from 268 to 364.Textural analysis indicates overlapping of early-diagenetic and multi-phase hydrothermal sulfide mineralization. Development of laminated pyrite and pyritized calcarenites suggests that this mineralization was generated during early diagenesis, close to the seawater-sediment interface in oxygen-poor conditions under the influence of low-temperature hydrothermal fluid circulation. Later hydrothermal cherts and replacive sulfides suggest discharge of relatively warm hydrothermal fluids during early to mid-diagenesis, presumed to be linked to movements of nearby normal faults. Similarities in mineralogy and S isotope compositions suggest genetic links between the sub-economic pyritic mineralization and the underlying Tara Deep deposit, and consequently, that the former represents a geochemical halo with direct applicability in exploration for Zn-Pb deposits.

Constraints on fluid evolution and growth processes of black smoker chimneys by pyrite geochemistry: A case study of the Tongguan hydrothermal field, South Mid-Atlantic Ridge

Up to now, the Tongguan hydrothermal field is the southernmost-distributed modern submarine massive sulfide discovered on the South Mid-Atlantic Ridge. A well-preserved black smoker chimney which contains three distinct concentric zones was collected from the active vent field. The external outer wall of the chimney contains mainly pyrite with minor sphalerite, chalcopyrite and galena. The sulfides within the internal middle layer consist of predominant pyrite, with lesser amounts of marcasite. The axial conduit is dominated by chalcopyrite, with minor pyrite. To clarify the ore-forming fluid evolution during the black smoker chimney growth, we performed detailed petrographic and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) studies on pyrite grains from the chimney. Seven types of pyrite: framboidal, relict, colloform, dendritic, massive, euhedral and lined pyrites, are identified from exterior to interior of the chimney.As shown by the results of LA-ICPMS, geochemical compositions of pyrite vary across the chimney. Generally, low-temperature elements (Mg, V, Mn, Pb, Zn, Ag and Tl) are enriched in pyrite in the outer wall of the chimney and decrease toward the interior zones. Elements indicative of high temperature conditions, such as Se and Te, show opposite trends and are enriched in pyrite within the inner zones of the chimney. Framboidal, relict, colloform and dendritic pyrites precipitate from low to mid temperature fluids (<250 °C), while massive and euhedral pyrites are products of ore-forming fluids characterized by mid to high temperature (250 to > 335 °C). Relict and lined pyrites have the same chemical signatures, suggesting that they precipitated under similar physicochemical conditions. The observed patterns are resulted from the changes in temperature and fluid chemistry caused by interactions of between seawater and hydrothermal fluids with each other in the chimney.Cobalt concentrations in pyrite from the modern black smoker chimneys located on the mid-ocean ridge apparently vary systematically in response to salinity change of vent fluids. The low Co contents (average 0.32 ppm) in pyrite suggest that the hydrothermal fluids vented from the black smoker chimney are Cl-depleted compared to seawater, most likely caused by phase separation. The systematic variations in geochemistry and morphology of the pyrite across the chimney reflect multiple stages of mineralization. Different degrees of fluid-seawater mixing and phase separation are the main controlling factors during the chimney formation.

Mineralization styles, alteration mineralogy, and sulfur isotope geochemistry of volcanogenic massive sulfide deposits in the Shadli Metavolcanics Belt, South Eastern Desert, Egypt: Metallogenic implications

Three distinct occurrences of Zn–Cu–Pb mineralization (Um Samiuki, Hilgit, and Maaqal) in Neoproterozoic island arcs of the Shadli Metavolcanics Belt, South Eastern Desert, Egypt, have been investigated in this study. The Shadli Metavolcanics Belt erupted in two magmatic cycles, with the Older Um Samiuki Metavolcanics group getting overlain by the Younger Hamamid Metavolcanics (YHM) group. The YHM group is characterized by two distinct cycles of volcanism. The studied deposits are mainly hosted by volcanic and volcaniclastic rocks that belong to the first cycle of the YHM group. The host-rock succession was interpreted to have been formed by back-arc extensional volcanism and was then deformed and metamorphosed to the lower greenschist facies. The relationship between the mineral occurrences and host rocks remains poorly constrained and controversial. We report new field observations, paragenetic data, mineral chemistry analyses, and in situ sulfur isotopes to characterize the sulfide mineralization and to gain insights into its genesis. Two mineralization styles have been identified in these deposits. The first style in the Um Samiuki deposit is expressed by two massive mineralized bodies that are mostly stratiform. It is distinguished by sphalerite, chalcopyrite, pyrite, galena, and Ag-bearing minerals; followed by bornite and covellite in decreasing abundance. Less abundant supergene phases include secondary copper minerals and iron oxyhydroxides. The hydrothermal alteration is characterized by sericitization, chloritization, epidotization, and silicification. The second style represents disseminated and vein-type sulfides mainly encountered in Hilgit and Maaqal occurrences. It is characterized by pyrite with minor sphalerite and chalcopyrite. The δ34SV-CDT values range from + 5.44‰ to + 9.08‰ with an average of + 8.11‰ ±1.1‰ (n = 18) for massive mineralized zones and from − 2.25‰ to + 3.78‰ with an average of + 1.06‰ ±2.3‰ (n = 8) for disseminated and vein sulfides. Such a variation in the sulfur isotope signatures may imply that both mineralization styles were derived from the thermochemical sulfate reduction (TSR) of seawater and leaching of basement lithologies in varying quantities, consistent with Volcanogenic Massive Sulfide (VMS) deposits of back-arc basins. The negative δ34SV-CDT values of some sulfides from the disseminated and vein mineralization may be seen as evidence for magmatic SO2 disproportionation. The studied VMS deposits display a close spatial and genetic association with submarine felsic volcanism of the YHM group, and their temporal distribution corresponds closely with the Mozambique Ocean closure stage of the Pan-African Orogeny.

Geochemistry and oxidative potential of the respirable fraction of powdered mined Chinese coals

This study evaluates geochemical and oxidative potential (OP) properties of the respirable (finer than 4 μm) fractions of 22 powdered coal samples from channel profiles (CP4) in Chinese mined coals. The CP4 fractions extracted from milled samples of 22 different coals were mineralogically and geochemically analysed and the relationships with the OP evaluated. The evaluation between CP4/CP demonstrated that CP4 increased concentrations of anatase, Cs, W, Zn and Zr, whereas sulphates, Fe, S, Mo, Mn, Hf and Ge decreased their CP4 concentrations. OP results from ascorbic acid (AA), glutathione (GSH) and dithiothreitol (DTT) tests evidenced a clear link between specific inorganic components of CP4 with OPAA and the organic fraction of OPGSH and OPDTT. Correlation analyses were performed for OP indicators and the geochemical patterns of CP4. These were compared with respirable dust samples from prior studies. They indicate that Fe (r = 0.83), pyrite (r = 0.66) and sulphate minerals (r = 0.42) (tracing acidic species from pyrite oxidation), followed by S (r = 0.50) and ash yield (r = 0.46), and, to a much lesser extent, Ti, anatase, U, Mo, V and Pb, are clearly linked with OPAA. Moreover, OPGSH correlation was identified by organic matter, as moisture (r = 0.73), Na (r = 0.56) and B (r = 0.51), and to a lesser extent by the coarse particle size, Ca and carbonate minerals. In addition, Mg (r = 0.70), B (r = 0.47), Na (r = 0.59), Mn, Ba, quartz, particle size and Sr regulate OPDTT correlations. These became more noticeable when the analysis was done for samples of the same type of coal rank, in this case, bituminous.

Constraints of Fe-S-C stable isotopes on hydrothermal and microbial activities during formation of sediment-hosted stratiform sulfide deposits

Microbial and hydrothermal venting activities on the seafloor are important for the formation of sediment-hosted stratiform sulfide (SHSS) deposits. Fe isotopic compositions are sensitive to both microbial and hydrothermal activities and may be used to investigate the formation of these deposits. However, to the best of our knowledge, no Fe isotopic studies have been conducted on SHSS deposits. In the Devonian Dajiangping SHSS-type pyrite deposit (389 Ma), South China, laminated pyrite ores were precipitated from exhalative hydrothermal fluids, whereas black shales were deposited during intervals with no exhalation. Pyrite grains from black shales mostly display positive δ56Fe-py (0.01–0.73‰), higher than marine sediments (ca. 0‰), due to pyrite deriving Fe from basinal shuttled Fe(III) (hydr-)oxides and slowly crystallizing in pores of sediments with equilibrium fractionation, except for negative δ56Fe-py (−0.17‰ to −0.24‰) of two samples caused by mixing of Fe from underlain laminated ores. The positive δ34S-py (3.50–24.5‰) of black shales reflect that sulfur of pyrite originated from quantitative reduction of sulfate in closed pores of sediments. In contrast, pyrite grains of laminated ores have negative δ56Fe-py (−0.60‰ to −0.21‰), which were not only inherited from the negative δ56Fe of hydrothermal fluids but also caused by kinetic fractionation during rapid precipitation of a pyrite precursor (FeS) in hydrothermal plumes. These ores have negative δ34S-py (−28.7‰ to −1.82‰), because H2S for pyrite mineralization was produced by bacterial sulfate reduction (BSR) in a sulfate-rich seawater column or shallow sediments.The δ56Fe-py values of laminated ores co-vary positively with δ34S-py and δ13C-carbonate along the ore stratigraphy, with δ13C-carbonate values ranging from −12.0‰ to −2.50‰. However, they correlate negatively with aluminum-normalized total organic carbon (TOC/Al2O3). Organic carbon is thus considered to enhance the production of H2S by BSR activities, increase pyrite precipitation rates and promote the expression of kinetic fractionation of Fe isotopes. Intriguingly, in the ore units with vigorous hydrothermal venting activities, δ56Fe-py, δ34S-py and δ13C-carbonate values display a consistently increasing trend. Such results suggest that venting hydrothermal fluids significantly inhibited the H2S production of BSR, which then reduced the pyrite crystallization rate and decreased the kinetic fractionation of Fe isotopes. Our study reveals that the formation of SHSS deposits relies on H2S from microbial activities and metals from hydrothermal exhalation on the seafloor, but that vigorous exhalation can inhibit microbial activities and thus sulfide precipitation rates. The integrated use of Fe, S, and C isotopes can effectively elucidate these dynamic interactions between hydrothermal venting and microbial activities during the formation of SHSS deposits.

Characteristics, kinetics, thermodynamics and long-term effects of zerovalent iron/pyrite in remediation of Cr(VI)-contaminated soil

Development of efficient, green and low-cost natural mineral-based reductive materials is promising to remediation of hexavalent chromium(Cr(VI))-contaminated soil. Considering the synergetic effect between pyrite and zerovalent iron (ZVI), an activated pyrite supported ZVI(ZVI/FeS2) with high reducing activity was developed by ball milling activation of natural pyrite and sulfidation of ZVI. The remediation property of ZVI/FeS2 for Cr(VI)-contaminated soil was evaluated with different ZVI/FeS2 dosage, soil-water ratio, initial pH, time and temperature, as well as the stability of Cr. The results showed that ZVI/FeS2 possessed high reduction activity with soil Cr(VI) removal rate up to 99 % even under alkaline condition, and soil with different pH values eventually converged to neutral after 90 days, indicating that ZVI/FeS2 has a good self-regulating alkaline ability. The reduction process conformed to Langmuir-Hinshelwood first-order kinetics and was a spontaneous and endothermic process. The lower activation energy of 17.97 kJ mol−1 (usually 60–250 kJ mol−1) indicated that the reduction reaction of Cr(VI) was particularly easy to occur. The speciation change of Cr in soil within 30 days demonstrated that the Cr in the soil was converted from a readily migratable state to a more stable state, where the Fe–Mn oxide bound fraction reached 85.03 % due to the generation of Cr(III)/Fe(III) co-precipitation. The results of long-term stability experiments showed that the leaching concentrations of Cr(VI) and total Cr decreased significantly after the ZVI/FeS2 treatment and remained stable at very low levels for 180 days. This study provided a sustainable way to fully utilize natural pyrite minerals to obtain iron-bearing reductive materials for feasible, effective and long-term stable immobilization of Cr(VI) in soil.

Mineralogy and Fluid Inclusions of the Cunas Emerald Mine, Maripí, Boyacá, Colombia

The Cunas mine is currently one of the major producers of fine emeralds in Colombia; its emeralds typically display a magnificent green hue, which is highly appreciated in the world market. The mineralization is found in vanadium-rich black shales of the Muzo formation; emeralds occur in pockets within hydrothermal veins and breccias, consisting mostly of calcite, dolomite, albite, quartz, and minor pyrite, parisite-(Ce), and fluorite; hydrothermal alteration is pervasive and dominated by albitization and carbonatization. Emerald-hosted fluid inclusions are highly abundant and remarkably large and complex. Poly-phase inclusions are ubiquitous, occur both in emeralds and gangue minerals, and consist of two daughter crystals (typically halite and calcite or siderite; exceptionally parisite-(Ce)), a liquid brine, a CO2-N2-CH4-rich gas bubble, and occasionally minor liquid CO2. Vapor-rich inclusions were observed in quartz, and two-phase inclusions were identified in calcite and dolomite, thus suggesting a complex fluid evolution. Microthermometry analysis indicates the emerald-forming fluids were trapped at relatively low temperature ≈ 260-340°C and pressure ≈ 875-2400 kbar, with relatively high density —1.03 g/cm³—, and elevated salinity 39% NaCl eq. Wt.; other aqueous components detected include CaCl2, KCl, and FeCl2. Based on these data, we propose the emerald mineralization at the Cunas mine was originated by the mixing of two hydrothermal fluids of different sources; one fluid with high salinity derived from evaporite dissolution, responsible for the albitization of the host rocks; the second is a calcium-rich fluid evolved from connate waters, which was equilibrated by the interaction with calcareous and organic-rich wall rocks. As a result, emerald mineralization took place at structurally favorable sites where fluid mixing was promoted. The described geological and physicochemical features for the Cunas mine, are in agreement with an epigenetic sediment-hosted mineralization —Colombian-type— formed by the circulation and mixing of relatively low-temperature non-magmatic fluids.

The La Pointe gold deposit, a disseminated orogenic gold deposit at the boundary between the La Grande and Opinaca subprovinces, Eeyou Istchee Baie-James, Québec, Canada

The La Pointe gold deposit is hosted by Neoarchean rocks metamorphosed to the amphibolite facies, straddling the boundary between the La Grande and Opinaca subprovinces, in Eeyou Istchee Baie-James (Québec, Canada). The deposit consists of two zones, Zone 25 and Zone 26, which are oriented WNW-ESE (S1) and have been deformed and folded by the main regional deformation (S2). Zone 25 is hosted by biotite-rich paragneiss of the Laguiche Complex (2710–2671 Ma) and the mineralization consists of disseminated native gold along with arsenopyrite, pyrrhotite, chalcopyrite and minor pyrite. The mineralization is associated with recrystallized alteration consisting of quartz, phlogopite, dravite ± titanite, microcline, muscovite and calc-silicate veins. Native gold occurs as inclusions in the metamorphically annealed alteration assemblages and at the margin of arsenopyrite. The low content of gold in arsenopyrite suggests re-equilibration at peak conditions during arsenopyrite recrystallization (325–531 °C) which expelled and crystallized native gold. Zone 26 is hosted in a grunerite-altered BIF of the Yasinski Group (2751–2725 Ma) and is characterized by disseminated pyrrhotite-arsenopyrite-löllingite-chalcopyrite in calcic amphibole-biotite-garnet-tourmaline ± chlorite host rocks. Native gold occurs as inclusions in peak metamorphic minerals (hedenbergite, garnet), or at the contacts between löllingite cores and arsenopyrite rims. The La Pointe deposit is interpreted as pre-peak metamorphic, disseminated orogenic gold deposit, subsequently overprinted by higher, amphibolite-grade, and late retrograde metamorphism.

ФЛОТАЦИОННЫЕ РЕАГЕНТЫ ДЛЯ ИЗВЛЕЧЕНИЯ ТОНКОВКРАПЛЕННОГО ЗОЛОТА ИЗ ТРУДНООБОГАТИМЫХ РУД И ТЕХНОГЕННЫХ ПРОДУКТОВ

At the present stage of development of the mineral resource base of precious metals, the wider involvement of refractory ores and technogenic products in the mineral processing is playing a very important role. It is due to these types of mineral resources the main Russian and foreign companies plan to get the increase in the production of gold and other precious metals. Refractory ores are characterized by low content and uneven distribution of valuable components, emulsion dissemination of gold, complex material composition, flotation active silicate and carbonaceous rock components. The main technologies for their processing include combined schemes that provide intensive preliminary preparation of ore, fine and ultrafine grinding. Creation of effective reagents for flotation of fine classes of noble metals, selective depression of gold-free sulfides, like pyrite, pyrrhotite, arsenopyrite, and rock minerals is one of the recognized innovative solutions for intensifying the enrichment process of this type of raw material. The studies performed at IPKON RAS in the framework of the scientific school of Academician V.A. Chanturiya helped to develop and substantiate the novel selective reagents-collectors of dithiocarbamate type (DEDTCm, OPDTC, DBDTC, MDTC) and herbal modifiers that possess complexing properties in relation to noble metals and provide an increase in the recovery of valuable components of gold by 5-7%. A set of analytical methods - scanning electron (LEO 1420VP, Carl Zeiss) and laser microscopy (KEYNCE VK-9700, Shimadzu), X-ray fluorescence spectroscopy (ARL ADVANT’X), ICP –MS (Agilent 725 ICP-OES, Agilent Technologies), X-ray diffractometry (DRON-2.0, XRD 7000, Shimadzu), potentiometry, titrimetric analysis, methods of mathematical statistics helped to study the adsorption layer of the reagents on natural minerals and model sulfides with micro- and nanosized gold. Using an original technique for quantitative assessment of the reagent coating by image analysis (SLM), the surface area of the mineral occupied by the reagent was calculated. A method for selective flotation of gold-containing sulfides using OPDTC and oak bark extract has been developed and tested in the separation of the collective gold-arsenic concentrate of the Olympiada deposit. It showed the possibility of obtaining a gold-pyrite concentrate with an arsenic content of less than 2%. The prospect of using plant modifiers for gold recovery during flotation of complex ores has been substantiated.

Corrosion Level of Rock Bolts Exposed to Aggressive Environments in Nordic Road Tunnels

For road tunnels in most Nordic countries, temporary rock support installed during tunnel excavation usually becomes a part of the permanent rock support. Rock bolts are the most common rock support measure in road tunnels excavated in hard rock, and their conditions over the period of tunnel operation play a significant role in the safety of these tunnels. The rock bolt types and aggressive environmental conditions considered in this research are focused on those used and observed in Norwegian and Swedish road tunnels. Findings elsewhere in similar environments are included to highlight the different kinetics of degradation. Based on the collected data, the corrosion levels in these road tunnels are comparable to those in the most polluted industrial areas. Aggressive groundwater conditions for rock bolts include a groundwater pH below four (which can be caused by sulfuric acid formation due to the oxidation of the mineral pyrite in the rock), marine groundwater, and flowing groundwater with a high concentration of dissolved oxygen. Furthermore, chloride-bearing deicing salts commonly used on roads located in cold climate regions during winter can promote corrosion in rock bolts from the tunnel room. For these environments, this research proposes a lognormal probability function to quantify the expected steel corrosion level for 25, 50, and 100 years of exposure time. The corrosion protection given by cement grouting, hot-dip galvanizing and epoxy coating are also addressed to explore their contributions to the lifespan extension of rock bolts in acidic and chloride-rich environments.

Faults caused by the fault: Microstructural and mineral characterization of deformation in Chungliao Tunnel, Taiwan, caused by Chishan Fault

This study employs microstructural and mineralogical characterization to analyze deformation within the Chungliao Tunnel (Formosan Freeway, Taiwan) caused by the movement along the Chishan Fault, as well as its effect on accelerated creep along the fault. The results reveal pyrite-filled fissures and a large amount of wavy extinction quartz and bent muscovite. The mineral particles are fragmented and finely granulated. Additionally, slippage between grains and dislocation creep are observed within Chishan Fault. Therefore, the primary deformation mechanisms of this fault are cracking/frictional sliding, dislocation creep, and grain-boundary sliding. The presence of calcite, clay minerals, physically absorbed water, and crystalline water in the rock enhances fault movement and significantly weakens the strength of rock layers. As a result, the Chungliao Tunnel over the past 18 years has risen at an average annual rate of 8 cm, and is now 130 cm higher than at the time of construction. This study is expected to contribute to future infrastructure planning along the fault. For example, mineral grains in the rock layer tend to align themselves along the fracture orientation, implying the possible stress direction. Moreover, the content of index minerals (e.g. calcite, pyrite, and clay minerals) in the rock layer can be utilized to predict the scale of rock-layer sliding and the severity of potential fault-related disasters.

Methanogenesis Potentials: Insights from Mineralogical Diagenesis, SEM and FTIR Features of the Permian Mikambeni Shale of the Tuli Basin, Limpopo Province of South Africa

Carbonaceous shale is more topical than ever before due to the associated unconventional resources of methane. The use of FTIR, SEM-EDX, and mineralogical analyses has demonstrated a promising approach to assess methanogenesis potentials in a more rapid and reliable manner for preliminary prospecting. Representative core samples from the borehole that penetrated the carbonaceous Mikambeni shale Formations were investigated for methanogenesis potentials. The absorption band stretches from 1650 cm−1 to 1220 cm−1 in wavenumber, corresponding to C-O stretching and OH deformation of acetic and phenolic groups in all studied samples, thereby suggesting biogenic methanogenesis. The CO2 was produced by decarboxylation of organic matter around 2000 cm−1 and 2300 cm−1 and served as a source of the carboxylic acid that dissolved the feldspar. This dissolution process tended to release K+ ions, which facilitated the illitization of the smectite minerals. The SEM-EDX spectroscopy depicted a polyframboidal pyrite structure, which indicated a sulfate reduction of pyrite minerals resulting from microbial activities in an anoxic milieu and causes an increase in alkalinity medium that favors precipitation of dolomite in the presence of Ca and Mg as burial depth increases. The contact diagenesis from the proximity of Sagole geothermal spring via Tshipise fault is suggested to have enhanced the transformation of smectite to chlorite via a mixed layer corrensite in a solid-state gradual replacement reaction pathway. The presence of diagenetic chlorite mineral is characteristic of low-grade metamorphism or high diagenetic zone at a temperature around 200 °C to 230 °C and corresponds to thermal breakdown of kerogen to methane at strong absorption band around 2850 cm−1 and 3000 cm−1, indicating thermal methanogenesis.

Superimposing mineralization in the Zhengguang Au-Zn deposit, NE China: Evidence from pyrite Re-Os geochronology, fluid inclusion, and H-O-S-Pb isotopes

The Duobaoshan orefield is located in the eastern part of the Central Asian Orogenic Belt (CAOB) and underwent multiphase magmatism and mineralization. The Zhengguang deposit in the orefield is characterized by porphyry copper mineralization and intermediate-sulfidation (IS) epithermal gold mineralization. The porphyry-type veinlet-disseminated sulfide mineralization (~480 Ma) is hosted in granodiorite/tonalite porphyries and hydrothermal breccias, and is associated with widespread potassic (K-feldspar and biotite) alteration. Three porphyry-type mineralization stages have been identified: (I-1) quartz + medium-fine grained pyrite, (I-2) quartz + pyrite + chalcopyrite, and (I-3) quartz + calcite + minor pyrite. The IS epithermal vein/veinlet-disseminated mineralization occurs in andesite porphyry and fractures of the Duobaoshan Formation volcanic rocks, and is associated with extensive silicic, sericitic, and pyrite-sericitic-silicic alterations and minor propylitic alteration. Three IS epithermal-type mineralization stages are identified: (II-1) quartz + coarse-grained pyrite, (II-2) quartz + polymetallic sulfides, and (II-3) quartz + calcite + barren sulfides. Five stage II-2 pyrite samples yielded a Re-Os isochron age of 246.0 ± 6.4 Ma (MSWD = 0.85), suggesting a Triassic Au mineralization event after the Ordovician Cu mineralization. Stage I-1 fluid inclusions (FIs) are predominantly of VL- and LV-type and minor SL-type, with homogenization temperatures (Th) of 283–359 ℃ and salinities of 0.3–35.1 wt%. Stage I-2 is characteristically composed of VL- and LV-type inclusions with Th of 193–296 ℃ and salinities of 0.8–14.2 wt%. Only VL-type inclusions occur in stage I-3, II-1, II-2, and II-3 with Th of 149–216 ℃, 213–285 ℃, 169–236 ℃, and 125–176 ℃, and salinities of 2.4–7.9 wt%, 6.5–12.2 wt%, 3.4–8.8 wt%, and 2.1–6.3 wt%, respectively. H-O isotopic compositions for the mineralization (Ordovician: δ18OH2O = -9.9 to −0.5‰, δD = -86 to −75.6‰; Triassic: δ18OH2O = -8.4 to −2‰, δD = −134.1 to −88.5‰) indicate two different evolving fluid systems, both with an initial magmatic source and a later meteoric water incursion. Sulfur and lead isotope (Ordovician: δ34S (−3.1 to −0.7‰), 206Pb/204Pb (17.570–17.613), 207Pb/204Pb (15.427–15.441), 208Pb/204Pb (37.258–37.294); Triassic: δ34S (-5.4 to −2.5‰), 206Pb/204Pb (17.627–17.965), 207Pb/204Pb (15.466–15.534), 208Pb/204Pb (37.468–37.703)) values suggest a dominantly magmatic and a mixed magmatic-sedimentary source for the Ordovician and Triassic mineralization, respectively.

Trapping of uranium by organic matter within sandstones during mineralization process: A case study from the Shuanglong uranium deposit, China

Carbonaceous debris (i.e., CD), dispersed organic matter (i.e., DOM) within sandstones, has been studied in the Shuanglong uranium deposit of the southern Ordos Basin, northern China. Relations of uranium enrichment and organic matter (i.e., OM) were investigated through maceral analyses, proximate analysis, vitrinite reflectance measurements, and morphology analyses of uranium minerals. The results show that CD widely distributed in sandstones, is associated with pyrite and uranium minerals. Macerals are mostly composed of telinite, collotelinite, collodetrinite, semifusinite, and inertodetrinite, including that collotelinite is dominant (contents more than 60%). The CD is at the stage of medium coalification, and is of low moisture, high ash, high volatile matter, medium fixed carbon, and high sulfur. Uranium occurs in uranium minerals (i.e., pitchblende and coffinite) and amorphous uranium. Moreover, uranium minerals partly or completely replace macerals. Statistical analyses show that porous inertinite and higher organic matter maturity is more advantageous to uranium enrichment. Additionally, uranium is unevenly distributed in macerals along certain directions, which is related to the physicochemical properties of macerals. Porous inertinite could provide channel for uranium-bearing fluid migration and space for uranium preconcentration. The CD at the stage of gas coal is of reducibility to be favorable for the forming of uranium minerals. Moreover, the relative atomic content of uranium (IV) increases with the increasing organic matter maturity. Uranium-bearing fluid could permeate into macerals under certain physical and chemical conditions, and react, i.e., adsorption followed by reduction. It is beneficial to comprehend the mechanism of uranium mineralization, providing certain guides for prospection.

Synthesis and characterization of pyrite mineral from rock deposits in Bantimurung Maros Regency of South Sulawesi

The study has successfully obtained the mineral pyrite (iron pyrite persulfide) and Hematite (Fe2O3) of the natural resources in the Bantimurung District, Maros, South Sulawesi. The method used in this purification is the hydrothermal method. Based on the characterization results, it was obtained pyrite mineral with high purity (more than 90%). Based on the analysis, this material has a cubic structure P a -3 with lattice parameters a = 5.4167 Å and a space structure for the hematite group -R 32 c with lattice parameters a = 5.048 Å, b = 5.048 Å, and c = 13,762 Å. These results are consistent with the surface morphology characterized using SEM with various magnifications showing uneven particle distribution with a particle size of 5 µm-100 nm. The results of characterization and analysis of XRF and XRD show that the degree of crystallization and homogeneity of natural material deposits in Bantimurung are rich in iron, magnesium (Mg), sulfur (S), which appear with a high percentage, and high value minerals such as molybdenum (Mo) and neodymium with a low percentage. With this composition, the materials in Bantimurung have the potential to be used as photovoltaic coatings in solar cell applications, production of sulfur dioxide, paper industry, manufacture of sulfuric acid, semiconductor materials, and applications in sodium and lithium batteries.

Mineralogical characterization and speciation of sulfur, zinc and lead in pyrite cinder from Bergvik, Sweden

Roasting of sulfide ores to produce sulfuric acid began on an industrial scale in the middle 1800′s and is still used extensively worldwide. The residual, pyrite cinders, have commonly been disposed in the environment where they pose a potential and serious threat to aquatic life. In this project, two profiles in a pyrite cinder deposit in Bergvik, Sweden, have been sampled and a comprehensive mineralogical characterization have been carried out. The objectives were to investigate the composition and morphology of pyrite cinder grains and the speciation of sulfur, Pb and Zn in the solid phase. Scanning electron microscopy showed pyrite cinder grains with a core of the ore minerals pyrite and sphalerite enclosed in layers of iron oxides/hydroxides (mainly hematite). XANES analysis, supported by X-ray diffraction analysis, SEM-EDS and bulk element analysis, showed that content of the residual sulfur in the cinder is mainly sulfides, 55–80%, predominately sphalerite. The remaining mass of sulfur is assumed to be adsorbed or precipitated as secondary sulfate minerals, predominantly associated with the grain surfaces. Calculated saturation indexes indicated barite, anglesite and perhaps aluminite. EXAFS spectroscopy indicated that about half of the Zn was bound to O and half was bound to S. LCF analysis of EXAFS spectra indicated that the main Zn species were sphalerite (40–50%) and franklinite (10–20%). The remaining Zn was associated with iron oxides/hydroxides and Zn minerals like hydrozincite or possibly zinc oxides. SEM-EDS analysis showed Pb precipitate located on both the surface of the grains and in the interior as inclusions. The analytical interpretation indicated anglesite.

The Effect of Aerophine 3418A Collector Dosage on Niğde (Ulukışla-Madenköy) Complex Pb-Zn Sulphide Ore Flotation

In this study, grinding + flotation experiments were performed on the sample of complex Pb-Zn sulphide ore taken from Niğde (Ulukışla-Madenköy) region in Turkey. According to the mineralogical analysis of the ore sample used in experimental studies, it was determined that the ore composition contains calcite, quartz, pyrite, chalcopyrite, hematite, goethite, limonite, gypsum, galena, sphalerite, jarosite, arsenopyrite and marcasite minerals. In addition, Au and Ag grains were found to be inclusions in hematite, goethite and jarosite minerals. The experiments were carried out at a solid ratio of 30%, a flow rate of 10 L/min, a stirring rate of 1250 rpm and pH = 9. In flotation tests, lime is used as the pH regulator, zinc sulphate, sodium silicate as the depressant, sodium isobutyl dithiophosphine as the collector and methyl isobutyl carbinol as the frother. In the flotation studies, the effect of Aerophine 3418A collector dosage on flotation was investigated. As a result, a lead concentrate of 55.13% Pb was obtained and it was found that this concentrate contained 2489 ppm of Ag. The amount of Aerophine 3418A collector was determined as 10 g/t.

Fluid source, element mobility and physicochemical conditions of porphyry-style hydrothermal alteration-mineralization at Mirkhani, Southern Chitral, Pakistan

The Cretaceous calc-alkaline granodioritic rocks in north-western Kohistan island arc host porphyry-type mineralization at Mirkhani in the Khyber Pakhtunkhwa province of Pakistan. In this paper, we present whole-rock geochemistry, mass-change calculations, and type and degree of element mobility regarding the hydrothermal mineralization-alteration processes. There are two distinct types of pyrite mineralization: (1) euhedral to subhedral pyrite (Py1) and cataclastic pyrite (Py2). To comprehend the source of hydrothermal fluids and their physicochemical conditions, trace element and S (sulfur) isotope compositions of the two types of pyrite were determined. Besides, the pyrite and silicate minerals were investigated through electron probe microanalysis (EPMA).The average low Ni (46), Zn (5), Cd (below detection level), and Bi (1) contents (in ppm), high Co/Ni ratio (>10) of both Py1 and Py2, and the range of sulfur isotope values for Py1 (−0.84‰ to 1.49‰) and Py2 (−0.93‰ to 1.84‰) indicate affiliation of the mineralization with felsic magma-derived hydrothermal fluids. The average low and high contents (ppm) of Se (0.7), As (2.6) and Zn (2), and Co (1089), respectively, in Py1 than Py2 (Se = 1.3, As = 4, Zn = 6 and Co = 747) indicates that former pyrite grains crystallized at a higher temperature than the latter, however, both types of pyrites were formed in medium to high-temperature conditions.The observed strong mobility of REE (rare earth elements) and HFSE (high field strength elements), high La/Yb ratios (avg. 23), and low (<1) Nb/La and Th/La ratios in the altered rocks reflect mobilization by slightly acidic solutions dominated by chloride and fluoride-rich complexes (±SO4 and OH). The gain-loss calculations reveal that SiO2, CaO, and TiO2 were leached out, whereas Al2O3, Fe2O3, MgO, P2O5, K2O, Cu, As, Mo, Ag, Au, Bi, and REE, HFSE, and LILE (large-ion lithophile elements) were variably added to the rocks during the hydrothermal process.Temperature calculation for chlorite formation and the type of gangue and ore mineral assemblage (epidote + sericite + albite + pyrite) implies a mineralization temperature range between ~ 215 °C and ~ 322 °C. The porphyry style of hydrothermal alteration-mineralization, trace element and S isotope composition of pyrite, and elemental gain and loss indicates that the mineralization at Mirkhani could be a part of a major porphyry Cu-Au system.

An experimental investigation into the oxidative dissolution of typical organic-rich shale from China

Oxidizing stimulation of organic-rich shale was proposed to enhance the rate of methane extraction from the matrix. Previous studies lacked attention on the dissolution characteristics of organic matter (OM) during the dissolution process performed using oxidative fluids. In this study, the organic-rich shale samples obtained from the Longmaxi Formation, Niutitang Formation, and Yanchang Formation were used for dissolution experiments. Crushed shale samples were treated with deionized water, hydrogen peroxide (H2O2), or sodium hypochlorite (NaClO) for 240 h, respectively. By using a combination of X-ray Diffraction, rock-eval pyrolysis, total organic carbon analysis, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, the composition and organic geochemical characteristics of the treated shale samples were determined. The results showed that H2O2 induces the dissolution of both the pyrite and carbonate minerals, and NaClO more readily dissolves pyrite and not carbonate minerals. Higher removal efficiency of OM for all four shale samples occurs when treated with NaClO than with H2O2. The oxidative dissolution of OM in these shale samples occurs as two dominant modes: one is the oxidation cracking of C–C, C–H such as in the Niutitang or Yanchange formations; the other is oxidation cracking of C–O, such as in the Longmaxi Formation samples. Both the Longmaxi Formation samples, which showed higher C–O contents compared to samples from the other two formations, exhibited better oxidizability than others when treated with H2O2 or NaClO. Oxidation products such as Fe2+/Fe3+ and H+ enhance the oxidizing ability of H2O2 and NaClO toward cracking of OM. However, the consumption of H+ due to the carbonate minerals may impair the oxidizing ability of H2O2, but not that of NaClO. Furthermore, the presence of an organo-clay complex has an adverse influence on the removal of OM. The results indicated that the type of OM, the content of the pyrite and carbonated minerals, and the physical protection of the organic carbon by clays should be taken into account, when selecting a shale reservoir suitable for oxidizing stimulation and associated optimization of the oxidant during the fracturing operation design.

Laboratory and field study on changes in water quality and increase in dissolved iron during riverbank filtration.

Changes in the water quality by the riverbank filtration (RBF) process were investigated in the field-scale demonstration sites. The overall water quality was improved by RBF, but Fe2+ concentration significantly increased in the riverbank-filtered water more than in the river water. This result would be caused by the interaction between the iron minerals and the river water in the aquifer and the influx of the hinterland groundwater into RBF wells. Dissolution properties of iron from the aquifer soils cored at the sites were evaluated through incubation experiment considering various values of redox potential (Eh), dissolved oxygen (DO), and hydrogen-ion concentration exponent (pH). These results presented that at the incubator with the final Eh of 470 mV, DO of 3.4, and pH of 4.53, the iron from the aquifer soil was most dissolved, and the pyrite and siderite contents in the aquifer soil decreased significantly from 11.5 to 6.22% and from 50.8 to 24.5%, respectively. Based on changes of ion concentrations (such as Fe2+, Fe3+, SO42- and NO3-) and iron species in the incubators, it was believed that pyrite and siderite minerals in the aquifer soils cause an increase in the Fe2+ concentration with the absence of DO and an increase in the Fe2+ and Fe3+ concentrations with the presence of DO. The dissolution rates of iron minerals into Fe2+ and Fe3+ were dependent on Eh, pH, and DO and were more sensitive to Eh and pH than DO. The results of this study can provide information on RBF site selection and its operation.