Mode Of Occurrence Research Articles

Uranium-Bearing Layers of Sandstone Type Uranium Deposits Identification and Three-Dimensional Reconstruction in the Northern Ordos Basin, North-Central China

Sandstone type uranium is the most valuable and has the most potential for mining among the known uranium deposits. In the process of forming, the hydrolytic migration and enrichment of uranium require special basin sedimentary environment and tectonic background. Therefore, the mineralization process of sandstone type uranium deposits has certain layering characteristics and distribution rules in the underground vertical depth space. It is important to mine the spatial distribution characteristics of vertical uranium-bearing layers, and thus, reconstruct the three-dimensions of uranium orebodies. In this paper, according to the metallogenic law and distribution characteristics of sandstone type uranium in the underground vertical space, a nonlinear uranium-bearing layers identification (NULI) method of sandstone type uranium is proposed by using different types, resolutions and scales of borehole data. Then, the depth of uranium mineralization for the Daying uranium deposit within northern Ordos Basin is identified accurately and the spatial distribution characteristics of the uranium-bearing layer on the exploration line are obtained. Finally, the occurrence mode of the underground uranium orebodies are presented by using three-dimensional reconstruction analysis. It provides a basis for the prediction, exploration and mining of sandstone type uranium deposits within the Ordos Basin.

Single phase to ground arcing fault identification based on wavelet packet energy

With the increasing proportion of cable lines in the distribution network, the capacitance current in the system increases, which leads to the single phase to ground arcing fault in the distribution network. However, at present, there is less research on single phase to ground arcing fault, and the type of grounding fault is always assumed to be metallic or resistive grounding, and the arcing ground fault is not identified in time, which leads to further expansion of the fault. In this paper, the transient simulation analysis of a single phase to the ground is carried out, and a new method to distinguish arcing ground fault from metal grounding fault using wavelet packet energy is proposed, which solves the problem of fault type identification. Through a large number of simulation data analyses and practical verification, it is shown that the method is not affected by the time of fault occurrence and neutral grounding mode, and has a strong anti-interference ability and high reliability.

Rare-Earth Minerals in Kaolin Ore, Mine Tailings, and Sands – Central Georgia, Upper Coastal Plain

AbstractThe total concentrations of rare-earth elements (REE) in the mined kaolin (0.02–0.06 wt.%), kaolin mine tailings (0.03–1.9 wt.%), and the kaolin-associated Marion Member sand lithology (0.03–4.6 wt.%) opened questions regarding the modes of occurrence of the REE and the role(s) of chemical weathering and secondary processes to explain the presence of REE in these materials. The REE were hosted primarily by phosphate minerals (monazite, xenotime) based on mineralogic analyses (scanning electron microscopy, X-ray diffraction). Enrichments in the light rare-earth elements (LREE: La–Gd) and the high correlation coefficient values were noted between P and the total REE concentrations (r2 = 0.99) for the sands and the mine tailings. Lower correlation coefficient values were noted between total REE concentrations and Zr (r2 = 0.31). The coarse fractions of the mined kaolins were enriched in the heavy rare-earth elements (HREE: Y, Tb–Lu) relative to the kaolin-associated sand lithologies. The REE inventory cannot be explained solely by mineral inheritance within the mined kaolins. Lower correlation coefficient values between P and total REE, positive Eu/Eu* anomalies, and the presence of xenotime overgrowths on zircon showed the importance of the role of chemical weathering of the detrital minerals during post-depositional processes (such as diagenesis) leading to redistributed and fractionated REE within the mined kaolin. The possibility of adsorption of the REE to kaolin mineral surfaces in the fine fraction of the mined kaolins remains open and permits further study to characterize fully the multi-modal fractionation of REE possible in the Georgia kaolin deposits.

Yttrium and REE Mineralization in Manganese Pods Occurring in Bentonite Deposits of the Eocene Texas Coastal Plain

AbstractEocene-aged bentonite deposits in Gonzalez (Texas, USA) carrfy scattered manganese oxide-rich pods where rare earth element (REE) concentrations as high as 7800 ppm have been detected — 10 times greater than in the already enriched bentonite. This study investigated the nature of the association between REEs and Mn oxides as well as REE modes of occurrence in these pods, in order to understand the processes that mobilize and accumulate REEs in the low-temperature depositional environment of the Texas coastal plain. Embedded, polished blocks of Mn pods were analyzed by Scanning Electron Microscopy (SEM); sections were then extracted by the FIB liftout technique from regions bearing REEs for further analysis by Transmission Electron Microscopy (TEM). The SEM and TEM results revealed the presence of abundant yttrium phosphate nanoparticles identified as xenotime, forming large globular aggregates that reach a few microns in diameter; these xenotime aggregates also host trace concentrations of Zr, Dy, Er, Yb, and Ce. Further, rhabdophane nanoparticles were detected that host predominantly light REEs and Y. The relative proportions of REEs in rhabdophane vary between particles and show decoupling of Ce from other light REEs, suggesting oxidation from Ce3+ to Ce4+. The REE enrichment of these Mn pods is due to extensive weathering along fractures cutting through the bentonite deposit that drove their remobilization and transport downward. At the base of the bentonite, where fractures terminate against the boundary with a cemented sandstone, changes in flow regime combined with gradual downward changes in fluid composition, prompted co-precipitation of Mn oxides and REE phosphates (xenotime and rhabdophane).

Strain and Stress Accumulation in Viscoelastic Splay Fault and Subducting Oceanic Crust

AbstractThis study constructs a model to represent the strain–stress field surrounding a splay fault and demonstrates the accumulation processes of both strain and stress around the splay fault. We consider the case of multiple fault dislocations, construct the model as a function of the effective viscosity in the media, and investigate the influence of the effective viscosity on the strain and stress accumulation patterns. The results show that the strain and stress tend to accumulate in the splay fault and the subducting oceanic crust, and the rate of accumulation varies with the effective viscosity. The accumulation and relaxation of strain and stress are simultaneous, and the slower the effective viscosity, the slower the accumulation rate. We discuss the relationship between the splay faults, fluid, and intraslab earthquakes. Finally, the possibility that effective viscosity may contribute to the mode of occurrence of intraslab earthquakes at the Hikurangi subduction margin is discussed.

Spatial analysis of moving-vehicle crashes and fixed-object crashes based on multi-scale geographically weighted regression

Previous researches have demonstrated that traffic crashes in urban areas are geographical events and strongly linked to local characteristics such as road network and land attributes. However, with a significant emphasis on moving-vehicle crashes, the spatial pattern of fixed-object crashes is unclear so far. The difference between these two types of crashes, and whether existing spatial tools such as geographically weighted regression can interpretate the occurrence mode have not been investigated before. To fill this gap, this paper focuses on understanding the spatial features and occurrence of these two types of crash, i.e., moving-vehicle and fixed-object on the city level. Crash data from Dalian, China were aggregated into subdistricts and calibrated with multi-scale geographically weighted regression (MGWR) models. A noticeable but similar clustering pattern was revealed in both types, with spatial overlap of their accident-prone regions. The spatial influence of explanatory variables (road network, geographic, demographic, socio-economic, and land-use variables) was also found mostly similar in both types of crashes. However, fixed-object crash in downtown is more affected by node count, while POI entrance/exit count, especially those in areas with more industrial zones tend to significantly reduce crash risk. In both types of crashes, terrain slope rather than elevation is found to mitigate the crash risk, especially in the downtown area. Compared to traditional Geographically Weighted Regression (GWR) with a fixed bandwidth, the improvement in modeling performance using MGWR highlights the reasonability and benefits to consider the influence scale of each contributing factor in urban spatial analysis of traffic collisions. This study could help transportation authorities identify high-risk regions, understand their contributing factors and take precautions for improving the local traffic safety.

Redistribution of uranium through lamprophyre intrusions in the Permo-Carboniferous coal of the northern Datong Coalfield, China

Magmatic intrusion is a key factor affecting the uranium concentration in coal. It has long been reasoned that magmatic intrusions generally enrich uranium in low-uranium coal. However, less attention has been paid to the redistribution of uranium in uranium-rich coal caused by magmatic intrusions. Thus, a total of 558 uranium data points obtained by spectrophotometric determination were collected from 57 boreholes in the northern Datong Coalfield, rich in lamprophyre intrusions, to determine their effect on the concentration and mode of occurrence of uranium in this Permo-Carboniferous coal. Coal in this area can be classified as either intrusion-affected or unaffected. The uranium concentration was relatively high in both unaffected coal and highly thermally affected coal, while relatively low in slightly thermally affected coal, indicating that lamprophyre intrusions redistributed the uranium in coal. The carbonate content within coal increased markedly with increasing degree of coalification caused by the intrusion. Uranium in unaffected coal was mainly associated with organic compounds, whereas that in intrusion-affected coal occurred mainly in secondary minerals (e.g., carbonates). The uranium concentrations in fresh lamprophyre and carbonatite veins, interspersed therein, were 0.23–0.86 μg/g and 0.97–2.34 μg/g, respectively, suggesting that higher concentrations of uranium in intrusion-affected coal may not have been directly derived from intrusions, but rather from hydrothermal processes at intrusion-coal contacts. The lamprophyre intrusions can reactivate, relocate, or enrich uranium initially complexed with organic matter. With an increase in the degree of coalification, active functional groups responsible for complexation are progressively broken down, resulting in decreased uranium concentrations. However, the uranium concentration was positively correlated with MgO and CaO contents in intrusion-affected coal, indicating that uranyl ions shedding from organic matter may be complexed and subsequently coprecipitated with secondary carbonate minerals.

Multiscale in-situ elemental characterization of critical elements in low rank coal, implications for modes of occurrence

This study investigated the distribution characteristics and modes of occurrence of rare elements (Li, V, Co, Mo, Ni, Sb, W, Nb), dispersed elements (Ga, Ge), and rare earth elements (REEs) in two selected coal samples: the Al-Li-Ga-rich coal from the Jungar Coalfield in the Ordos Basin, China, and the Ge-rich coal from the Shengli Coalfield in the Erlian Basin, China. Multiscale in-situ elemental characterization techniques, including BSE-EDS, EMPA mapping, and LA-ICP-MS mapping, were used for this purpose. The results showed that in the Al-Li-Ga-rich Jungar coal, Li was mainly associated with kaolinite with various origins, dominated by epigenetic kaolinite, followed by syngenetic kaolinite. Gallium was highly concentrated in organic matter, led by collodetrinite, followed by collotelinite. The majority of Nb was associated with organic matter, while a minority was distributed in Al-bearing minerals, including boehmite and epigenetic and syngenetic kaolinite. In the Ge-rich Shengli coal, Ge, W, and Sb were consistently distributed in coal and concentrated in organic matter, mainly semifusinite. V was widespread in organic matter, including textinite, fusinite, and semifusinite. Cobalt, Mo, and Ni occurred in a similar distribution and were associated with organic matter, led by collodetrinite in the Al-Ga-rich coal and cutinite in the Ge-rich coal. REEs, except for La and Ce, were associated with organic matter, led by vitrinite in Al-Ga-rich coal and huminite in Ge-rich coal. Lanthanum and Ce were highly concentrated in La, Ce-rich minerals, even if they were widespread in organic matter as well. The visualized results of this study confirm most of the previous findings obtained from indirect analyses but also reveal some differences. Gallium was rarely detected in Al-rich minerals such as boehmite and kaolinite, but highly concentrated in organic matter. Lithium was detected in both epigenetic and syngenetic kaolinite. Ge, W, and Sb were organically associated and concentrated in semifusinite in Shengli Ge-rich coal. Overall, this study provides a way to determine the modes of occurrence of trace elements in organic matter in coal, and these findings could be applied to coal from other geological backgrounds.

Bacterial and Antimicrobial Susceptibility in Bloodstream Infections

Bloodstream infections (BSI) have a fatality rate of up to 70%, are among the top ten causes of death worldwide and are an important cause for concern. Along with fungal infection, they can come from bacteria, viruses, and protozoa. Bacteria are responsible for the majority of BSI. The study was aimed to identify bacterial profile, antimicrobial susceptibility patterns as well as factors associated with BSI suspected patients which include incidence and mode of occurrence, detection methods, disease mechanism, common diseases, and treatment options. BSI can be further classified into sepsis and septic shock Based on the degree of organ failure and the overall onset of drug-resistant bacteria-related mortality and morbidity. The prevalence of bloodstream infections (BSI) is attributed to several variables such as patient age at admission, an increase in patients with broader immunity, and the introduction of virulence factors by bloodstream pathogens and factors related to infection prevention and control strategies and their implementation. The distinction between BSI is made based on their mode of occurrence which often involves chills, low blood pressure, changes in mental state, fever, hypothermia, excessive sweating, and the possibility of organ malfunction. Falciparum, UTIs (Urinary Tract Infections), MRSA Bacteremia, and Methicillin-resistant Staphylococcus aureus are common illnesses caused by BSI. Treatments include routine vaccinations, oral therapies, bacteremia management for MRSA bacteremia as well as anti-staphylococcal treatment. Treatment for bacteraemia remains challenging despite advances due to the pathogenicity of the organism, weak response to antibiotics, and rising multidrug resistance. As a result, combinational therapy is receiving more attention as a means of treating these infections.

Occurrence Modes of Critical Metals (Li+ and Ge4+) in the Organic Molecular Structures of Coal: A Density Functional Theory Study.

To explore the mechanism of critical metal (Li+ and Ge4+) occurrence in the organic molecular structures of different rank coals, simulations were investigated using quantum chemical density functional theory. In this paper, Wender lignite, bituminous, and anthracite molecular models were used as organic molecular structures in coal. The electrostatic potential (ESP), frontier molecular orbitals, and Mulliken charges were used to identify adsorption sites in organic molecular structures. Mulliken charge, bond length, Mayer bond order (MBO), and adsorption energy values were used to estimate the binding conformation and strength between organic molecular structures and critical metals (Li+ and Ge4+). The results showed that the negative ESP, the highest occupied molecular orbitals, and negative Mulliken charges in the organic molecular structures were located at the O atom of oxygen functional groups and the aromatic structures, respectively, which were the active sites for critical metal adsorption. Mulliken charge transfer, bond length, MBO, and adsorption energy data suggested that the binding of Li+ with organic molecular structures was controlled by the carbonyl group (C=O), while the aromatic structures had less effect on the occurrence of Li+ in the organic molecular structures. The maximum adsorption energy value for binding Li+ with organic molecular structures was -742.16 kJ/mol. The Ge4+ ions not only showed strong binding ability with oxygen functional groups, but also Ge4+ formed thermodynamically stable half-sandwich complexes with aromatic structures. Therefore, the coal rank had little effect on the binding of Ge4+ with organic molecular structures. Moreover, the binding of Ge4+ with organic molecule structures was enhanced by the synergistic interactions of oxygen functional groups and aromatic structures. The adsorption energy values were up to -8511.43 kJ/mol. The adsorption of organic matter in coal to critical metals (Li+ and Ge4+) generated changes in the spatial configuration of the organic molecular structure, including local twisting of the organic molecular structure in lignite and bending of the aromatic structure in anthracite.

Mineralogy and enrichment of critical elements (Li and Nb-Ta-Zr-Hf-Ga) in the Pennsylvanian coals from the Antaibao Surface Mine, Shanxi Province, China: derivation of pyroclastics and sediment-source regions

As a critical element, lithium plays an important role in a wide range of modern industries and in particular, battery storage and new energy technologies. Lithium in coal has attracted much attention in recent years because some coals are highly enriched in this element and consequently their corresponding coal combustion products may provide anm alternative source for this element. Previous studies showed that highly enriched Li in coals is generally associated with chlorite group minerals and in most cases attributed to the action of hydrothermal solutions. This paper provides mineralogical and geochemical data on the No. 9 Coal, the major minable coal from the Antaibao Surface Mine, Ningwu Coalfield, Shanxi Province, northern China, and focuses on the modes of occurrence and source of Li in this coal. The No. 9 Coal is a medium ash, medium sulfur, high volatile bituminous coal. The mineralogy of the No. 9 Coal is dominated by kaolinite, calcite, and pyrite, with minor amounts of anatase, rutile, goyazite, quartz, illite, boehmite, and bassanite, and traces of orthoclase, zircon and galena. The studied coal samples are characterized by high contents of Al2O3 (39.80% on average) in comparison with average Chinese coals, and high concentrations of Li, Ga, Se, Zr, Nb, Ta and Th compared with world hard coals. In addition to Li and Al, the critical elements Nb, Ta, Zr, Hf, and Ga in this coal also have a potential economic significance. The geochemical indicators (high Al2O3/TiO2, low Nb/Yb ratios and the specific rare earth element distribution patterns) and the mineral compositions (e.g., very low content of boehmite) indicate that the mineral matter in most coal benches and host rocks is dominantly derived from the Precambrian calc-alkaline granites of the Yinshan and northern Trans North China Orogens, and possibly from the bauxite of the Benxi Formation. Additionally, the geochemical and mineralogical characteristics of the intra-seam partings and some coal benches (quartz-free, kaolinite-dominated mineralogy, high Al2O3/TiO2 and Nb/Yb values) indicate that they were derived from an alkaline intermediate-felsic volcanic source. The highly enriched Li in the studied samples mainly occurs in kaolinite and is attributed to the input of material from sediment-source regions, rather than hydrothermal fluids. In addition, interaction of terrestrial and marine waters may have promoted the Li enrichment process in the partings.

Silurian black shales from Sousel-Barrancos Metallogenic Belt (Ossa-Morena Zone, Portugal): Characterization and interplay to Cu deposits

Black shales are commonly spatially associated with metal-rich deposits, wherein organic matter in these rocks may condition or influence the processes related with the concentration of metals and formation of ore deposits. In the Ossa-Morena Zone (South of Portugal), namely in the Sousel-Barrancos metallogenic belt, several Cu mineralized veins occurs, being generally hosted in Silurian metasedimentary units mainly composed of black and grey shales, with interbedded lyddites and black quartzites. This research aims to contribute to the study of the association between those Silurian black shales and the Cu ore deposition in the Sousel-Barrancos metallogenic belt. The petrographic, geochemical and mineralogical analysis of black shales was performed to characterize the organic and inorganic fractions, to investigate elements concentration and its mode of occurrence. The data allow to identify the spatial pattern of thermal maturation of these black shales related to the variability of metamorphic processes, and the studied samples collected in drill cores from Miguel Vacas deposit also allow to identify an irregular pattern of maturation associated to the pathway of hydrothermal fluids. A significant Cu enrichment in black shales in the supergene enrichment domains were identified and data seems to indicate that Cu concentration is not directly related with organic carbon content, probably indicating a distinct source for Cu content. The mobilization of hydrothermal fluids, possibly of magmatic source, contributed to the discrepant maturation of organic matter in black shales.

Provenance of multi-stage volcanic ash recorded in the Late Carboniferous coal in the Jungar Coalfield, North China, and their contribution to the enrichment of critical metals in the coal

The origins of partings within the Late Carboniferous No. 6 coal in the Jungar Coalfield, North China, and their relationship to the enrichment of critical metals in the coal, is poorly understood. This study combines UPb ages and LuHf isotope data of zircon, whole-rock geochemistry, LA–ICP–MS elemental mapping, and selective chemical extraction experiments to investigate the provenance of the partings and the occurrence mode of critical metals in the partings collected from the exploration area in the northwest of the Jungar Coalfield. It was found that the zircons in the kaolinite-dominant partings yielded a single age group of ca. 300 Ma at the latest Carboniferous (Gzhelian), indicating that the partings are alteration products of air-fall volcanic ash (tonsteins). The zircons are characterized by negative εHf(t) values and a continental arc tectonic setting, suggesting a genetic connection between the volcanic ash and the Late Paleozoic continental arc that existed in the Inner Mongolia Paleo-Uplift, related to the southward subduction of the Paleo-Asian oceanic plate beneath the northern margin of the North China Block. During the devitrification of volcanic glasses to kaolinite in the mires, the incompatible elements, such as Nb, Ta, Zr, Hf, and rare earth elements (REEs and Y, REY), preserved in the volcanic glasses were leached out as they are incompatible with the crystal lattice of kaolinite. Niobium and Ta, similar to Ti in ionic radii, were preferentially incorporated into fine-grained Ti oxides as reprecipitated products in the alteration process of volcanic ash. The enrichment of Nb, Ta, and Ti in organic matter in the tonsteins suggests that they have some mobility during alteration of volcanic ash and could be, to some extent, transported into the enclosing peats. Zirconium, Hf, and REY were fixed by organic matter admixed with the volcanic ash after their deposition in the mires. Meanwhile, they could also be transported into the enclosing peats, as no secondary minerals formed could substantially retain them. Although Li and Ga were able to be incorporated into the crystal lattice of kaolinite during their crystallization, they could also be transported into the enclosing peats due to their fluid-mobile nature. Both the leaching of a voluminous amount of volcanic ash contacting with the peats and the input of the volcanic ash as an admixture into the peats contributed to the enrichment of critical metals in the Late Carboniferous coal in the Jungar Coalfield.

Sphalerite as a non-traditional critical metal source: Correlative microscopy (EPMA, EBSD, and APT) of cobalt-enriched sulfides from the sediment-hosted copper-cobalt Dolostone Ore Formation deposit, Namibia

Sphalerite from the sediment-hosted Dolostone Ore Formation (DOF) Cu-Co-Zn deposit, in northwestern Namibia, has previously been shown to contain extremely high concentrations of the critical metal Co (up to 1 wt%). These concentrations are the highest reported in sphalerite to date, and the how and why of sphalerite being able to incorporate such high concentrations of Co are poorly understood. We use correlative electron probe microanalysis, electron backscattered diffraction, and atom probe to reconstruct the likely incorporation mechanisms and modes of occurrence of such high Co concentrations in natural sphalerite. While over twenty samples were studied, the comprehensive analytical workflow was executed on one representative sample to gain a detailed understanding of Co enrichment. The sulfides of the studied sample are Co-rich pyrite, chalcopyrite, Co-rich sphalerite, linnaeite, cobaltpentlandite, and cobaltite, mentioned in order of abundance. Detailed petrography of these sulfides indicates that they formed through three stages during the main Cu-Co-Zn ore stage of the DOF. Cobalt was initially contained in pyrite that grew during Ore Stage 1 and was later affected by oxidizing fluids (Ore Stage two). This led to remobilization and growth of linnaeite (Co2+Co3+2S4). A later change in fO2 (Ore Stage three) led to the breakdown of linnaeite and the further growth of accessory cobaltite along with the Co-rich sphalerite and chalcopyrite. The hyper-enriched Co-sphalerite then is the last major sink for Co in the DOF deposit. A low Fe and Co and high Zn sub-grain boundary network within the Co-rich sphalerite was identified by EPMA and EBSD. This sub-grain network is believed to have formed during a later, secondary metamorphic stage (Cu-Zn (-Pb) Ore Stage 4), which developed during ductile deformational mineralization styles such as pressure shadows and veins. Our APT data reconstructions show no evidence for Co-inclusions within the Co-sphalerite, and spatial ion correlation analyses of the data suggest that Co occurs in the sphalerite through simple substitution of Zn. This study demonstrates that sphalerite may contain significant concentrations of the Co through simple substitution, potentially representing an important non-traditional Co source in future critical metal exploration.

Thermal and Chemical Evolution of an Archean Collision Zone: Insights from P–T–t History of Mafic Granulites from the Coorg Block, S. India

Abstract Knowledge of pressure–temperature–time (P–T–t) evolution of Archean high-grade (deep crustal) metamorphic rocks is important for deciphering the nature of Archean tectonic processes. However, exposures of such rocks are limited in the present rock record. Here, we study a suite of high-grade, mafic rocks that are present along a crustal-scale shear zone (called the Mercara Shear Zone) between two Archean terrains of India, the Coorg block and the Dharwar Craton. Given that the Mercara Shear Zone is dated to be Mesoarchean, these shear zone rocks are well suited to elucidate Archean orogenic processes. Petrological investigation shows that these mafic rocks are characterized by a granulitic assemblage of orthopyroxene, clinopyroxene, plagioclase, quartz and amphibole ± garnet, and with accessory phases such as apatite, ilmenite, magnetite and rutile in some cases. We distinguish the investigated rocks into low-Mg and high-Mg varieties based on their whole-rock composition as well as their mode of occurrence in the field and mineral chemistry. This difference in the bulk composition led to different reaction histories—for example, the low-Mg mafic granulites underwent partial melting while high-Mg granulites were less fertile. Combining these observations with the results of geothermobarometry, phase equilibria modeling, geochronology (U–Pb in zircon and Lu–Hf in garnet ) and diffusion modeling, we have reconstructed a multi-stage P–T–t history for these rocks. The first phase (Stage 1) is represented by granulite-grade metamorphism at ~750–900°C and 8–13 kbar during ~3100 Ma (with uncertainties permitting a timing as recent as ~2700 Ma), after which they resided at T <500°C, likely at lower crustal levels (Stage 2). Subsequently, these rocks were reheated to a T of 700–750°C at 7–10 kbar at ~2400 Ma (Stage 3) and then again cooled down to ~500–600°C at 6–8 kbar (Stage 4). Application of diffusion chronometry shows that (1) the cooling rates of these granulites at high temperatures (>600°C) varied in the range of 25–50°C/Ma, and (2) the rocks resided for a long duration (~500 million years) at the Stage 2 metamorphic conditions, i.e. at T <500°C. We infer that such a protracted, high-T metamorphic history involving at least two heating pulses, and the relatively slow cooling rates on the order of 10’s °C/Ma are consistent with the operation of peel-back styled orogenesis (an embryonic form of plate tectonics) on an early hotter Earth (Mesoarchean to Paleoproterozoic). Moreover, the controls of bulk rock compositions on reaction histories provide a mechanism for intracrustal differentiation and generating Mg-rich, refractory material that may have eventually formed the lower continental crust over a protracted and pulsed thermal evolution spanning several hundred million years.

Failure analysis of fiberglass cover used for photovoltaic plants

AbstractCover boxes with inspection glass are generally used outdoors for photovoltaic systems. Sometimes these boxes break, during normal use. High temperature, thermal stress, cyclic stress, and cracking contribute to weakening the polymeric inspection “glass”. The study presents an interdisciplinary analysis to discover the mode of occurrence and causes of the failure. First, the material is accurately characterized. Then its mechanical behavior is characterized in a virtual scenario that reconstructs the real external environment. The goal is to build a new cover with inspection boxes that exhibits superior life cycle behavior when exposed to harsh weather conditions and atmospheric agents. The breaking phenomena of solar panels covering boxes in PMMA (Poly Methyl Methacrylate) are examined. Environmental stress is the main responsible for cracking. Styrene is employed in the polymerization process of Sheet Molding Compound (SMC); the diffusion of this material is the main responsible for cracking. Comprehensive engineering analysis shows how the thermoplastic component fails after being exposed to atmospheric agents. The PMMA “glass” is one of the polymers most sensible to the crazing phenomena.

Polymetallic Uranium Mineralisation in Rohil, Rajasthan, Western India: Insights from Mode of Occurrences, Structural Controls, Alteration Geochemistry and Exploration

Geological and radiometric studies of outcrops aided by extensive subsurface exploration through drill holes in an otherwise soil-covered terrain revealed the existence of low grades, medium tonnage, and metasomatite types of polymetallic uranium deposits at Rohil in India. Microscopic studies, electronprobe micro analyses, and geochemical analyses of samples from lodes indicate the polymetallic nature of mineralisation involving copper and molybdenum, in addition to uranium. Wide variations in the composition of fluid (S-, F-, P-, and O-rich) led to the formation of sulphides, fluorite, U-phosphosilicate, quartz, and magnetite, respectively, and are associated with uraninite. Litho-geochemical analyses from the Rohil deposit indicate multifarious metasomatic alterations associated with polymetallic mineralisation occurring in veins. The major mineralogical and metasomatic controls on rock compositions and the extent of material transfer processes that influenced the host rocks and mineralisati on are quantified by molar element ratio studies and alteration plots. General element ratio (GER) diagrams on chemical analyses of rock samples reveal albitisation and chloritisation as major and microclinisation, sericitisation, carbonatisation, and silicification as minor wall rock alterations associated with ore mineralisation. The alteration box plot between the chlorite–carbonate–pyrite index (CCPI) and the Ishikawa alteration index (AI) indicates the influence of hydrothermal activity and dominance of both albitisation and chloritisation. The ore zone is controlled by meso- and microstructures and the geometry of the soda- and potash-metasomatised zone around hydrothermal veins. This zone contains several anastomosing mineralised veins defined by a prominent joint that is set in quartzite that strikes subparallel to the axial surface of the F2 isoclinal folds and the pervasive schistosity S1 in the quartz–feldspar–biotite schist. Aventurisation of albite and microcline, established through electron probe micro analyses, can be considered as a pathfinder for uranium mineralisation. The close association of uranium and metallic sulphide mineralisation with microstructural, mineralogical (albitisation, chloritisation, and microclinisation), and geochemical variations can be applied as suitable exploration guides in a similar geological set-up worldwide.

The mechanism study on the integrated process of NaOH treatment and citric acid leaching for rare earth elements recovery from coal fly ash

Rare earth elements and yttrium (REY) have vital functions in the global economy because of their numerous applications. Coal fly ash (CFA) is considered a potential alternative resource for REY. In this paper, sequential chemical extraction procedure, NaOH treatment, and citric acid leaching were used to study modes of occurrence, enrichment, and recovery of REY in CFA after physical separation. The proportion of REY (84%) bond to aluminosilicate phase in the separated sample is higher than that in the raw CFA. Monazite, apatite, scheelite, and aluminosilicate phase were proved to be REY carriers via SEM-EDS observation. REY in CFA was enrichment by NaOH treatment, and the glassy phase dissolution conformed to shrinking core model. The dissolution was first controlled by a chemical reaction and then inner diffusion, with activation energies of 70.89 and 3.21 kJ/mol and reaction orders of 1.02 and 0.73, respectively. The gel conjunction and zeolite generation limited CFA dissolution, concluded from the chemical reaction verification, SEM observation, and XRD analysis. The REY content after multi-step NaOH treatment increased to 2135 μg/g with an enriched factor of 2.08. Citric acid (0.05 mol/L) leaching was investigated and REY recovery is 55%. A conceptual integrated process of NaOH treatment and citric acid leaching for the CFA utilization was designed. This paper will provide a theoretical fundamental and technological support for REY recovery.

Anomalous Enrichment of As and Hg in Underground Coal Dust: A Case from Xishan Coalfield, Shanxi Province, North China.

Coal dust is an important source of coal workers' pneumoconiosis, which is harmful to the health of underground workers. The coal dust samples were directly collected using a coal dust sampler from four major production positions in the underground coal mine. The particle size distribution, mineralogy, and occurrence of As and Hg in the coal dust samples were investigated. The results indicated that the contents of As and Hg were depleted or normal in the parent coal samples compared with the average values of C-P coal in North China and Chinese coal, but they were anomalously enriched in coal dusts. The concentrations of As and Hg in the coal dust samples studied are greater than the values of the elements in the parent coal. The As content in the coal dust samples studied is about one to three orders of magnitude above the parent coal value and the Hg content in the studied coal is 1.28 to 20.28 times higher than the parent coal value. The modes of occurrences of As and Hg were studied by sequential chemical extraction in combination with field emission scanning electron microscopy-energy dispersive spectroscopy (FESEM-EDS) and high-resolution transmission electron microscopy-EDS (HRTEM-EDS). The occurrence of As is dominated mainly by pyrite and secondarily by carbonate and silicate in the coal dust samples. Pyritic Hg and organic Hg may be the dominant forms in mining face and heading face samples, and carbonate and pyritic Hg are the main forms in rocks roadway and return airway samples. It is considered that the mechanochemical effect resulted in the formation of surface active sites and modification of the morphology. Harmful trace elements, such as As, Cd, Hg, Se, Pb, Co, Sb, and Tl, and minor grains associated with nanominerals that bear much hazardous elements, could easily be originally fractionated or adsorbed by airborne particulates. This research aims to provide a theoretical basis for the prevention of occupational disease and underground environmental evaluation.

Enrichment Characteristics of Hazardous Trace Elements in Feed Coal and Coal Ash in Huaibei Area under Leaching.

This research focused on the hazardous elements in the main coal seam of Huaibei coalfield, China. Through collecting 20 feed coal samples from different coal seams of nine coal mines in the region, and combining with XRF, XRD, ICP-MS, and sequential chemical extraction, the mineral composition and the contents of major elements and HEs for feed coal were analyzed. Compared with previous research results, the enrichment characteristics of HEs in feed coal were revealed. The leaching behaviors of Se, Hg, and Pb in feed coal and coal ash under different leaching conditions were analyzed in depth by using a leaching device independently developed. Results showed that, compared with Chinese coals and World coals, the content of other elements, except Se, Sb, Hg, and Pb, in feed coal of Huaibei coalfield were at the "Normal" level, and no "Low" level elements were found; as the acidity of leaching solution decreased, the relative leaching rate of Se (LSe) was gradually increasing, while the LHg and LPb were not obvious; the LSe in feed coal and coal ash had a great relationship with the modes of occurrence of Se. The difference in the Hg content in the ion exchange state in feed coal may be an important reason for the difference in Hg leaching behavior. However, the content of Pb in feed coal had little influence on its leaching behavior. The modes of occurrence of Pb determined that the LPb in feed coal and coal ash was not high. The LSe increased with the increase in acidity of leaching solution and leaching time. The leaching time was the main influencing factor of the LHg and LPb.