High Pyrite Content Research Articles

Mineralogy and inorganic geochemistry of the Es4 shales of the Damintun Sag, northeast of the Bohai Bay Basin: Implication for depositional environment

Abstract The Es4 shale, namely the fourth member of the Shahejie Formation deposited during the Eocene, is one of the most important hydrocarbon source rocks widely distributed in the Bohai Bay Basin. Twenty-nine samples with TOC ranging from 1.59% to 7.50% were gathered from the Es4 shale at the Damintun Sag. Compositions of mineralogy, major oxides, trace elements and REEs were analyzed to study their provenance, paleo-environment and tectonic setting. The Es4 shales show (La/Yb)N ratios ranging from 10.98 to 14.24 with an average of 12.45, and have similar C1-chondrite normalized REE + Y distribution to intermediate ~ mafic igneous rocks developed at the northeast NCC (North China Craton) during the Mesozoic and the Cenozoic. Weight ratios of Al2O3/TiO2, TiO2/Zr and Cr/Th of the Es4 shales show values of 12.76–18.81, 71.2–147.8 and 12.96–19.91, which reveal a common source of detritus from intermediate igneous rocks. The Es4 shales present values of K2O/Al2O3, ICV (Index of Compositional Variability), PIA (Plagioclase Index of Alteration) and CIA (Chemical Index of Alteration) locating at 0.07–0.21, 0.80–2.04, 39.82–83.85 and 44.76–76.15, respectively. These weathering proxies imply that the Es4 shales underwent moderate to intense weathering. Sensitive redox indicators, pyrite (1.7% ~ 12.6%) and TOC (1.59% ~ 7.50%), indicate a reduced depositional condition. TOC of the Es4 shales is positively correlated with U/Th and negatively correlated with (La/Yb)N, which indicates that organic matters were largely preserved at more reduced conditions and could be diluted by detritus influx. Absolute ratios of U/Th (0.11–0.25), V/Cr (0.80–1.46) and Ni/Co (2.42–4.40) suggested an oxic environment, which is contrary to the conclusion supported by high TOC content and existence of pyrite. These absolute ratios of U/Th, V/Cr and Ni/Co are probably inherited from parental rocks rather than reflecting redox conditions in this study. Shale samples showing higher TOC content are either accompanied with higher U/Th, lower Sr/Ba and lower (La/Yb)N, which demonstrates that organic matters are preserved in a deeper, fresh and reduced water environment. Plots of K2O/Na2O-SiO2, SiO2/Al2O3-K2O/Na2O, La-Th-Sc, Th-Sc-Zr/10 and Th-Co-Zr/10 indicate a tectonic setting of oceanic island arc or continental island arc.

Determination of the influence of pyrite on coal spontaneous combustion by thermodynamics analysis

In order to uncover the effect of pyrite on the tendency of coal to spontaneously combust, thermal analysis was carried out to characterize the reaction process of coal with different pyrite contents at four heating rates of 5, 10, 15, and 20Kmin−1 in air flow from 25 to 900°C. The Flynn-Wall-Ozawa method was applied to calculate the activation energy of coal with different pyrite contents. The results show that the thermogravimetric (TG) curve of coal samples can be divided in four stages, being water evaporation, oxygen absorption, thermal decomposition and burnout. As the mass fraction of pyrite content increased, the ignition point of the coal samples decreased and the weight loss rate during the thermal decomposition phase diminished. Meanwhile, the exothermic peak and mass loss peak moved toward lower temperatures. The peak values in the derivative thermogravimetric (DTG) and differential scanning calorimetry (DSC) curves shifted to higher temperatures with higher ignition and burnout temperatures under faster heating rates, but the whole curve shape was not affected. The apparent activation energies of the coal samples declined with higher pyrite contents, so the spontaneous combustion of coal can be promoted by pyrite.

XAS combined with Py-GC study on the effects of temperatures and atmospheres on sulfur release and its transformation behavior during coal pyrolysis

YanZhou (YZ) coal with comparably high organic sulfur and high pyrite content was selected to investigate the effects of temperatures on sulfur release and its transformation during pyrolysis under Ar and CO2 atmospheres. Pyrolysis connected with gas chromatography (Py-GC) was used to analyze the sulfur containing gases of H2S, COS and SO2, and the sulfur transformation during pyrolysis was measured by Sulfur K-edge X-ray absorption spectroscopy (S-XAS). For YZ raw, deashed and depyrited coals, desulfurization ratios gradually increase with the increasing temperatures, while their char yields gradually decrease under both atmospheres. Under Ar atmosphere, minerals in YZ coal have catalytic effect on the decomposition of sulfurs. However, the effect of minerals on sulfur decomposition is different under CO2 atmosphere. Under CO2 atmosphere, the release amounts of H2S, COS and SO2 for each sample are higher than that under the Ar atmosphere and the difference becomes more significant after 600 °C. This suggests that CO2 atmosphere is more helpful for the decomposition of stable sulfur at comparatively higher temperatures. Based on the analysis of Sulfur K-edge XAS, CO2 atmosphere can promote the decomposition of stable FeS and thiophenes during pyrolysis. Thus, based on the analysis of Py-GC and Sulfur K-edge XAS, CO2 atmosphere is more beneficial for the release of sulfur containing gases and for the decomposition of stable sulfur than Ar atmosphere. This provides detailed information about the effects of temperatures on sulfur release and transformation behavior during pyrolysis under CO2 atmosphere.

Using image logs to identify fluid types in tight carbonate reservoirs via apparent formation water resistivity spectrum

Hydrocarbon-bearing zone identification of tight reservoirs plays a crucial role in hydrocarbon exploration and development. However, tight carbonate reservoirs are generally characterized by complex lithology, low porosity, strong heterogeneity, and weak fluid logging responses, which present a major challenge to detect hydrocarbon-bearing zones using conventional methods. To address this challenge, this paper develops a new method defined as Rwa spectrum, taking advantage of the high vertical resolution and borehole coverage of the image logs. The Rwa spectra can be derived from the histogram distribution of the apparent resistivity values of formation water (Rwa) in a sliding window, combining the Simandoux equation and the triple-porosity model. The results show that a very broad Rwa spectrum with long tails corresponds to hydrocarbon-bearing zones, and the peak shape of it is flat. In contrast, the narrow Rwa spectrum corresponds to water-bearing zones, and the peak shape of it is a sharp spike. Furthermore, two Rwa spectrum parameters, namely AVERAGE (reflects the size of main peak values) and VARIANCE (reflects shape changes of the Rwa spectra) are defined to quantificationally detect hydrocarbon-bearing zones. For oil zones in Yingxi field, the AVERAGE had a value higher than 10 and the VARIANCE was higher than 10. And for water zones, the AVERAGE had a value lower than 4.5 and the VARIANCE was lower than 5. The resistivity values decrease linearly with the increase in pyrite content of the reservoirs of high pyrite content, which disturbs the response to resistivity values from different fluid types (oil, gas or water). Hence, this method is suitable for the formation of no or little pyrite contents (lower than 0.2), and the case where the salinity value of drilling mud is similar to that of formation water. Moreover, the method has been validated by production test data, providing unusual perspectives on the identification of fluid types in tight carbonate reservoirs.

Sedimentary and geochemical characteristics of the Triassic Chang 7 Member shale in the Southeastern Ordos Basin, Central China

The Ordos Basin is the largest petroliferous basin in China, where the Chang 7 Member shale serves as the major source rock in the basin, with an area of more than 100,000 km2. So far, sedimentary and geochemical characterizations have rarely been conducted on the shale in shallow (< 1000 m) areas in the southeastern part of the basin, but such characterizations can help identify the genesis of organic-rich shale and promote the prediction and recovery of shale oil. In this paper, several outcrop sections of the Chang 7 Member in the Tongchuan area were observed and sampled, and sedimentary and geochemical characterizations were conducted for the well-outcropped YSC section. The study results show that the Chang 7 Member shale is widely distributed laterally with variable thickness. The organic-rich shale is 7–25 m thick in total and exhibits obvious horizontal variation in mineral composition. In the eastern sections, the shale contains organic matter of Type II2–III and is low in thermal maturity, with high clay mineral content, low K-feldspar content, and no pyrite. In the western sections, the shale contains Type II1 organic matter and is low in thermal maturity, with high clay mineral, K-feldspar, and pyrite contents. The YSC section reveals three obvious intervals in vertical mineral composition and organic abundance. The Chang 7 Member organic-rich shale (TOC > 10%) contains mainly sapropelite and liptinite, with Type II kerogen. It is generally characterized by a hydrocarbon potential of more than 70 mg/g, low maturity, and shallow–semideep lacustrine facies. In the western sections, the shale, still in a low maturity stage, has a higher hydrocarbon potential and is optional for shale oil recovery. However, the Chang 7 Member shale in the study area is highly heterogeneous and its shale oil recovery is practical only in the organic-rich intervals.

Genesis of the Bianjiadayuan Pb–Zn polymetallic deposit, Inner Mongolia, China: Constraints from in-situ sulfur isotope and trace element geochemistry of pyrite

The Southern Great Xing'an Range (SGXR) which forms part of the eastern segment of the Central Asian Orogenic Belt (CAOB) is known as one of the most important Cu-Mo-Pb-Zn-Ag-Au metallogenic belts in China, hosting a number of porphyry Mo (Cu), skarn Fe (Sn), epithermal Au-Ag, and hydrothermal vein-type Ag-Pb-Zn ore deposits. Here we investigate the Bianjiadayuan hydrothermal vein-type Ag-Pb-Zn ore deposit in the southern part of the SGXR. Porphyry Sn ± Cu ± Mo mineralization is also developed to the west of the Ag-Pb-Zn veins in the ore field. We identify a five-stage mineralization process based on field and petrologic studies including (i) the early porphyry mineralization stage, (ii) main porphyry mineralization stage, (iii) transition mineralization stage, (iv) vein-type mineralization stage and (v) late mineralization stage. Pyrite is the predominant sulfide mineral in all stages except in the late mineralization stage, and we identify corresponding four types of pyrites: Py1 is medium-grained subhedral to euhedral occurring in the early barren quartz vein; Py2 is medium- to fine-grained euhedral pyrite mainly coexisting with molybdenite, chalcopyrite, minor sphalerite and galena; Py3 is fine-grained, subhedral to irregular pyrite and displays cataclastic textures with micro-fractures; Py4 occurs as euhedral microcrystals and forms irregularly shaped aggregate with sphalerite and galena. LA-ICP-MS trace element analyses of pyrite show that Cu, Pb, Zn, Ag, Sn, Cd and Sb are partitioned into pyrite as structurally bound metals or mineral micro/nano-inclusions, whereas Co, Ni, As and Se enter the lattice via isomorphism in all types of pyrite. The Cu, Zn, Ag, Cd concentrations gradually increase from Py1 to Py4, which we correlate with cooling and mixing of ore-forming fluid with meteoric water. Py2 contains the highest contents of Co, Ni, Se, Te and Bi, suggesting high temperature conditions for the porphyry mineralization stage. Ratios of Co/Ni (0.03–10.79, average 2.13) and sulphur isotope composition of sulfide indicate typical hydrothermal origin for pyrites. The δ34SCDT values of Py1 (0.42‰–1.61‰, average 1.16‰), Py2 (–1.23‰ to 0.82‰, average 0.35‰), Py3 (–0.36‰ to 2.47‰, average 0.97‰), Py4 (2.51‰–3.72‰, average 3.06‰), and other sulfides are consistent with those of typical porphyry deposit (–5‰ to 5‰), indicating that the Pb-Zn polymetallic mineralization in the Bianjiadayuan deposit is genetically linked to the Yanshanian (Jurassic–Cretaceous) magmatic-hydrothermal events. Variations of δ34S values are ascribed to the changes in physical and chemical conditions during the evolution and migration of the ore-forming fluid. We propose that the high Sn content of pyrite in the Bianjiadayuan hydrothermal vein-type Pb–Zn polymetallic deposit can be used as a possible pathfinder to prospect for Sn mineralization in the surrounding area or deeper level of the ore field in this region.

ПИРИТИЗАЦИЯ ПОРОД ЗОН ПЕРЕХОДА БАЖЕНОВСКОЙ СВИТЫ ВО ВМЕЩАЮЩИЕ ОТЛОЖЕНИЯ В ВЕРХНЕЮРСКО-НИЖНЕМЕЛОВОМ ЗАПАДНО-СИБИРСКОМ БАССЕЙНЕ

In the transitional zones from the Bazhenov Formation and to the enclosing deposits the complex of litological-geochemical researches, including the analysis of sections structure, distributions of C/S ratio and redox indicators (degree pyritization, authigenous uranium, Mn/Al) were made. It is defined that rocks on the borders with the Bazhenov Formation at the enclosing deposits are low carbonaceous with rather high content of pyrite; in the Bazhenov Formation near its roof in many cases rocks are characterized by approximately equal high contents of pyrite and kerogen. It is established that the pyritization of rocks on these intervals resulted by thermochemical sedimentation of iron from solutions on redox geochemical barriers without participation of bacterial activity.

Interplay of S and As in Mekong Delta sediments during redox oscillations

The cumulative effects of periodic redox cycling on the mobility of As, Fe, and S from alluvial sediment to groundwater were investigated in bioreactor experiments. Two particular sediments from the alluvial floodplain of the Mekong Delta River were investigated: Matrix A (14 m deep) had a higher pyrite concentration than matrix B (7 m deep) sediments. Gypsum was present in matrix B but absent in matrix A. In the reactors, the sediment suspensions were supplemented with As(III) and SO42−, and were subjected to three full-redox cycles entailing phases of nitrogen/CO2, compressed air sparging, and cellobiose addition. Major differences in As concentration and speciation were observed upon redox cycling. Evidences support the fact that initial sediment composition is the main factor controlling arsenic release and its speciation during the redox cycles. Indeed, a high pyrite content associated with a low SO42− content resulted in an increase in dissolved As concentrations, mainly in the form of As(III), after anoxic half-cycles; whereas a decrease in As concentrations mainly in the form of As(V), was instead observed after oxic half-cycles. In addition, oxic conditions were found to be responsible for pyrite and arsenian pyrite oxidation, increasing the As pool available for mobilization. The same processes seem to occur in sediment with the presence of gypsum, but, in this case, dissolved As were sequestered by biotic or abiotic redox reactions occurring in the Fe–S system, and by specific physico-chemical condition (e.g. pH). The contrasting results obtained for two sediments sampled from the same core show that many complexes and entangled factors are at work, and further refinement is needed to explain the spatial and temporal variability of As release to groundwater of the Mekong River Delta (Vietnam).

BIOENSAIOS COM OLIGOQUETAS EDÁFICOS PARA AVALIAÇÃO DA EFICÁCIA DO TRATAMENTO DE RESÍDUOS DE MINERAÇÃO DE CARVÃO EM CENÁRIO DE DISPOSIÇÃO TERRESTRE

A oxidação da pirita presente nos rejeitos e estéreis da mineração de carvão pode desencadear uma drenagem ácida, induzindo uma redução drástica do pH dos solos e sistemas aquáticos vizinhos. O presente trabalho trata da avaliação da eficácia do processo de tratamento de um resíduo de mineração de carvão coletado na região carbonífera sul catarinense. O tratamento aplicado consistiu na separação das partículas conforme sua densidade, gerando três frações: pesada, mista e leve; com alto, intermediário e baixo teor de pirita, respectivamente. A eficácia do tratamento foi avaliada com base na quantificação de metais pesados e execução de bioensaios agudos e crônicos com oligoquetas edáficos (Eisenia andrei), conforme protocolos padrão (ISO). Os bioensaios foram somente aplicados à fração mista do resíduo, devido ao volume de material gerado com necessidade eventual de disposição terrestre. Misturas desta fração mista com um solo artificial foram preparadas nas seguintes proporções: 0, 6, 12, 24 e 50%. Os resultados revelaram, de forma geral, uma redução das concentrações de metais pesados e atenuação do pH para as frações mista e leve, em comparação ao resíduo in natura, sugerindo que, do ponto de vista químico, o tratamento foi eficiente. As concentrações de metais nas misturas de solo com a fração mista do resíduo estavam em concordância com os valores do CONAMA para qualidade de solos. Os bioensaios agudos com oligoquetas revelaram ausência de mortalidade e de perda de biomassa dos animais, indicando baixa ecotoxicidade aguda. Contudo, os animais sobreviventes foram capazes de bioacumular elevadas quantidades de níquel na maior testada (50%), um metal reconhecidamente tóxico aos oligoquetas. O bioensaio crônico indicou perda significativa de biomassa para a dose de 50%, bem como redução significativa da reprodução para as doses de 24 e 50%. Tendo em vista a ocorrência de toxicidade somente para altas dosagens de resíduo no solo, o tratamento aplicado parece ser eficiente.

Different partitioning behaviors of molybdenum and tungsten in a sediment–water system under various redox conditions

Molybdenum (Mo) and tungsten (W) are redox-sensitive elements that exhibit contrasting geochemical behaviors under different redox and/or sulfidic conditions despite belonging to the same group in the periodic table. In this study, the geochemistry of Mo and W in a sediment–porewater system was investigated using a core sample collected from sediment containing hydrothermal minerals (Izena Hole, Okinawa, Japan). The Mo contents in the sediment and the porewater were quantified to calculate the partition coefficient Kd (concentration ratio of the solid phase to the aqueous phase) for Mo. However, the W concentration in the porewater was exceedingly low to be detected. Thus, we also conducted laboratory experiments simulating the sediment–porewater system to clarify the partitioning behaviors of Mo and W under redox conditions. X-ray absorption near-edge structure (XANES) spectra were obtained to determine the chemical species of Mo and W in sediment at different depths to understand the chemical processes of Mo and W. In particular, high-sensitivity XANES spectroscopy using wavelength-dispersive fluorescence mode was applied to W L3 edge XANES spectra to reduce the interference signals from coexistent elements (Zn and Ni). This step thereby facilitating the identification of oxygen- and sulfur-coordinated species for W in the sediments.The collected core sample covered a broad range of redox conditions under various hydrogen sulfide (H2S) concentrations depending on the depth. The presence of iron oxides in the upper layer suggested an oxic condition above within 4cm depth below the seafloor (cmbsf). Iron and Zn sulfide minerals were found in deeper layers (16–24 cmbsf) and indicated the reductive conditions formed in such layer. Hydrogen sulfide was also observed in the porewater of the deeper layer. Analyses for Mo in the natural sediments, as well as XANES analyses, revealed that the Kd was higher in the deeper layer, with high pyrite and H2S contents, than in the upper layer. These results implied that Mo was removed from the porewater under reductive and/or sulfidic conditions. The chemical species of Mo was also an oxygen-coordinated species in the upper layer (0–8 cmbsf). Meanwhile, the detection of sulfide in the deeper layer suggests that Mo sulfidation is an important reaction in Mo enrichment in sediments.On the other hand, at all the depths, W formed oxygen-coordinated species in the sediment. The subtle change of Kd for W with depth suggested that H2S did not affect the W adsorption in our samples. Hence, the Mo/W ratio in the sediments increased with the development of reducing conditions and vice versa in the coexistent porewater. Speciation analysis revealed that the high stability of oxygen-coordinated species of W was responsible for the variations of the Mo/W ratio under various redox conditions.

Geotechnical properties of polymer-amended tailings solvent recovery unit (TSRU) oil sands tailings

Fine tailings from the tailings solvent recovery unit (TSRU) in the Athabasca oil sands are known to contain a relatively high pyrite content and a high residual hydrocarbon content, which may alter their geotechnical properties. Little is known about TSRU tailings properties and therefore the potential for subaerial deposition. The goal of this study was to investigate the geotechnical properties of untreated, polymer-amended, and sand-mixed TSRU tailings to provide information for the consideration of subaerial deposition and increase the general knowledge about these unique tailings. The polymer-amended tailings had more desirable properties for subaerial deposition, including a lower final void ratio, less energy required to desaturate, and higher compressibility, when compared with the untreated tailings. The sand-mixed samples enhanced these properties, but may pose issues for transportation. The mineralogy indicated that the polymer-amended TSRU tailings have a high-enough pyrite content for acid generation, which may pose environmental issues for subaerial deposition. Overall, TSRU tailings exhibited different geotechnical properties when compared with the well-studied mature fine tailings, highlighting the need for further studies to provide information for the management of TSRU tailings.

Recovery of Copper from Pyritic Copper Ores Using a Biosurfactant-Producing Mixotrophic Bacterium as Bioflotation Reagent

In an attempt to investigate the use of bacteria and their metabolites as bioflotation reagents for environmentally friendly mineral processing, laboratory cell flotation tests were carried out using copper sulfide ores bearing a high content of pyrite, which were mixed with a biosurfactant-producing mixotrophic bacterium as bioflotation reagents. The interaction of bacterial cells and their metabolic products with the sulfide ores resulted in the alteration of the surface chemistry of both ores and bacterial cells as evidenced by FTIR and SEM-EDS observations as well as surface tension and contact angle measurements. The change in the surface properties of the sulfide ores in turn enabled the bacterium to function as flotation bioregeants in the flotation of copper sulfide ores as a function of bacterial cell concentration, conditioning time, flotation time and pH. Overall, the bacterium and its metabolites as bioreagents yielded flotation recoveries which might be attributed to the multi-function of the bacterium as depressant, collector and frother. Thus, the bacteria tested in this study could potentially be used as flotation bioreagents, providing an alternative to conventional flotation reagents.

Anaerobic Carbon Mineralisation Through Sulphate Reduction in the Inner Shelf Sediments of Eastern Arabian Sea

Monsoon-induced coastal upwelling, land run-off, benthic and atmospheric inputs make the western Indian shelf waters biologically productive that is expected to lead to high rates of mineralisation of organic matter (OM) in the sediments. Dissimilatory sulphate reduction (SR) is a major pathway of OM mineralisation in near-shore marine sediments owing to depletion of other energetically more profitable electron acceptors (O2, NO3−, Mn and Fe oxides) within few millimetres of the sediment-water interface. We carried out first ever study to quantify SR rates in the inner shelf sediments off Goa (central west coast of India) using the 35S radiotracer technique. The highest rates were recorded in the upper 10 cm of the sediment cores and decreased gradually thereafter below detection. Despite significant SR activity in the upper ∼12 to 21 cm at most of the sites, pore water sulphate concentrations generally did not show much variation with depth. The depth integrated SR rate (0.066–0.46 mol m−2 year−1) decreased with increasing water depth. Free sulphide was present in low concentrations (0–3 μM) in pore waters at shallow stations (depth <30 m). However, high build-up of sulphide (100–600 μM) in pore waters was observed at two deeper stations (depths 39 and 48 m), 7–11 cm below the sediment-water interface. The total iron content of the sediment decreased from ∼7 to 5 % from the shallowest to the deepest station. The high pyrite content indicates that the shelf sediments act as a sink for sulphide accounting for the low free sulphide levels in pore water. In the moderately organic rich (2–3.5 %) sediments off Goa, the measured SR rates are much lower than those reported from other upwelling areas, especially off Namibia and Peru. The amount of organic carbon remineralised via sulphate reduction was ∼0.52 mol m−2 year−1. With an estimated average organic carbon accumulation rate of ∼5.6 (±0.5) mol m−2 year−1, it appears that the bulk of organic matter gets preserved in sediments in the study region.

Composition and pore characteristics of black shales from the Ediacaran Lantian Formation in the Yangtze Block, South China

The Ediacaran period was critical in the evolution of the biosphere and ocean in the history of the Earth. Shales rich in organic matter (OM) are well developed for this period in the Yangtze Block, China, and have recently been related to shale gas exploration in South China. To date, detailed characterisation of the Ediacaran shales is not available. The present work sets out a detailed investigation of the composition and pore characteristics of samples from a shallow drill core in the Ediacaran Lantian Formation in the Lower Yangtze area, and the effects of shale composition on the pore growth are discussed. The 90-m-thick Lantian black shales are highly over-mature (equivalent vitrinite reflectance (EVRo) value approximately 4.0%) with a total organic carbon (TOC) content up to 12%. They are dominated by quartz (33–72%), generally with low clay or feldspar content (<20%) and highly varied carbonate content (up to 60%). The Lantian shales are also notable for their high pyrite content (up to 19%), suggesting a depositional environment of an anoxic water body rich in sulphates; greatly enriched OM is facilitated in deep-water environments. Bulk porosities of the shales range from 1.0% to 7.9%, and are positively correlated with TOC content. High-magnification scanning electron microscopy (SEM) images support the crucial importance of OM content on pore development. Generally, pore volume shows excellent, positive correlation with TOC content for micropores, good correlation for mesopores, and relatively poor correlation for macropores. Two samples with mostly high TOC content showed very low macropore volume and medium mesopore volume. These results suggest a close relationship between OM with relatively small pores, and enhanced compaction effect on large pores in highly OM-enriched shales.

Assessing metal transfer to vegetation and grazers on reclaimed pyritic Zn and Pb tailings.

A study of the concentrations of zinc and lead in an engineered soil capping system overlying sulphide mine tailings was undertaken. Tailings geochemistry, soil cover and vegetation were monitored over a 4-year period, and a cattle grazing demonstration exercise was conducted over a 1-year period. Whilst the tailings had a relatively high pyrite content and demonstrated oxidation, a circum neutral pH was observed for the duration of the study period due to the high dolomitic content. No evidence of metal mobility into the soil cover and vegetation was observed over the monitoring period. Relatively high Zn herbage content is attributed to the glacial till component of the soil cover. Similarly, no evidence of metal transfer to grazing cattle was observed through blood and tissue analysis with Zn content not significantly different from control animals. Pb tissue content was below limit of detection.

A fault controlled, newly discovered Eskişehir Alpu coal basin in Turkey, its petrographical properties and depositional environment

Recent findings suggest that Turkey contains about 15 billion tons of coal within its borders. A small proportion of it (NW part) is bituminous, but the rest is sub-bituminous and lignite coal. About 80% of the coals are utilized in power generation. The newly found coal field, Alpu Basin, contains about 1.3 billion tons of coal. The coal basin is a fault controlled and deeply buried basin which is close to the industrial areas in Turkey.In the studied area, there are two coal horizons in the Middle Miocene aged m2 unit. The average mineable coal seam thickness is approximately 13–14m. In order to determine the coalification degree, petrographic composition and depositional environment of the coals, petrographic and XRD analyses were conducted on coal samples taken from three boreholes which were drilled by MTA in the Eskişehir–Alpu Basin. According to the ASTM classification, the rank of the coals is sub-bituminous. Alpu coals contain two prominent types of maceral assemblages: either containing high amounts of funginites, macrinites, ulminite and gelinites, or high amounts of liptinites associated with detrital huminites (attrinite and densinites). The first type exhibits rather more homogeneous features, but the second has a more complex, mixed appearance with detrital macerals, intensive lineation, laminations and considerably higher pyrite contents. The Alpu coals contain montmorillonite, heulandite, α-quartz, pyrite, gypsum, kaolinite, illite, illite–montmorillonite, orthoclase and clay minerals which indicate variation in the pH conditions. The tissue preservation index (TPI) and gelification index (GI) indicate a limnic environment. The sample points are located between open marsh and clastic marsh areas on the TPI–GI diagram. This case indicates that the water table was variable during the coal formation.

Transformations of pyrite in different associations during pyrolysis of coal

The samples of pure pyrite, the mixtures of FeS2 or FeS loaded on a low-ash coal char, and an acid-washed coal with high content of pyrite were used to investigate the transformations of pyrite with different physical associations during pyrolysis. The presence of low-ash coal char, although affected the evolution of sulfur-containing gases in vapor phase, had little influence on thermal decomposition of pyrite at 450–650°C. Pyrite conversion above 920°C, especially transformation of the formed FeS into elemental iron, was facilitated primarily by the char matrix entity. During pyrolysis of coal, isolated agglomerates of single pyrite crystals were transformed into individual aggregates in the gaps of coke grains, while most of pyrite embedded in the coal particles or located at the edge of coal particles decomposed to the Fe–S phases which remain inside or closely in contact with the carbon matrix. Meanwhile low-sulfur Fe–S phases in the pyrolysis products of coal were mainly represented as FeSy (0<y<1).

Proposal for Reducing Emissions of SOx in Cement Plants

In the cement industry, emissions of sulfur oxides, nitrogen, carbon dioxide and water are inherent in the manufacturing process. However, there are limits to the amount of SO<SUB><i>x</i></SUB> and NO<SUB><i>x</i></SUB> emissions; the inhalation of such substances entails risks to human health, and their interaction with the atmosphere results in the formation of sulfuric acid and nitric acid, causing acid rain. These emission limits are even more severe when there is co-processing in the production process. SO<SUB><i>x</i></SUB> emissions can be formed by burning fuel, but they can also be present in the raw materials used. The presence of sulfur-based compounds in the raw materials has a great impact on the cement industry, owing to the large amount of limestone used in the process, especially when the deposits have a high content of pyrite (FeS<SUB>2</SUB>). One of the barriers encountered in the process of environmental licensing for co-processing is the high level of SO<SUB><i>x</i></SUB> emissions. To decrease these emissions and to enable co-processing in a cement industry, tests were performed, using abatement with lime (CaO). By varying the conditions of the manufacturing process, it was possible to obtain a reduction of up to 90% of the SO<SUB><i>x</i></SUB> emissions. With the implementation of this technique, SO<SUB><i>x</i></SUB> emissions reached values that met the legal limits, which could enable the start of co-processing in the industry.

Importance of oxidation during regrinding of rougher flotation concentrates with a high content of sulfides

The objective of this study is to understand the flotation behavior of copper and gold minerals after regrinding the rougher flotation concentrate with a high pyrite content. It was found that low Eh and dissolved oxygen (DO) were produced after regrinding due to the quick consumption of oxygen by the large amount of fresh pyrite surfaces created, resulting in poor flotation of copper and gold and their selectivity against pyrite. A number of methods were used to provide an oxidizing condition, including pre-aeration before flotation, regrinding in an oxidizing condition, and addition of different oxidizing agents during regrinding. It was found that all the oxidizing methods improved the flotation of copper and gold, however, the effectiveness of these methods varied from case to case. This study demonstrates the importance of oxidation during or after regrinding for the flotation of rougher flotation concentrates with high sulfide contents.

Composition and mode of occurrence of minerals in Late Permian coals from Zhenxiong County, northeastern Yunnan, China

AbstractMinerals in the Late Permian coals from the Niuchang-Yigu mining area, Zhenxiong County, northeastern Yunnan, China, were investigated using optical microscopy and low temperature ashing plus X-ray diffraction (LTA + XRD). The results showed that minerals in the coal LTAs are mainly quartz, kaolinite, chamosite, mixed-layer illite/smectite (I/S), pyrite, and calcite, with trace amounts of marcasite, dolomite, and bassanite. The authigenic quartz generally occurs in collodetrinite or as a filling in cleats or cell cavities. This silica was mainly derived from aqueous solutions produced by the weathering of basaltic rocks in the Kangdian Upland and from hydrothermal fluids. The presence of β-quartz paramorph grains in collodetrinite probably indicates that these grains were detrital and came from a volcanic ash. Clay minerals are generally embedded in collodetrinite and occur as cell-fillings. Pyrite occurs as framboidal, anhedral, and euhedral grains and a cell-filling. The coals are high in pyrite and the high pyrite content probably results from seawater invading during the stage of peat accumulation. Calcite generally occurs as vein-fillings, indicating an epigenetic origin.