Metal Grades Research Articles

To Study the Requirement of Implementation of Zero Waste Management Plan for Steel Production Plant (A Review)

Unsustained mining practices have resulted in the overuse of shared resources this year, degrading the environment extensively. Additionally, there is an increase in nursery gas emissions from the generation of vital metals due to a continually growing demand for metals, a decline in metal grades, and complex underused stockpiles. As a result, the mineral preparation and metal production industry frequently finds itself under increasing pressure to advance the overall sustainability of its operations, notably through reducing energy consumption, outflows, and waste transfer. Large volumes of wastewater are released by the steel and press industries. Typically, a quantitative approach is used to assess the wastewater's natural effects. In any event, a more notable factor in the harm to the natural environment is the water quality of released effluent. Furthermore, there is still a gap in the thorough assessment of several contaminants in wastewater in terms of both quantity and quality. This work considers the volume of wastewater and the quality of primary forms in order to characterize an add-up to natural affect score that surveys the natural impact of wastewater release. A field check and estimation of wastewater release volume and quality is carried out to secure pH, suspend solids chemical oxygen request add up to nitrogen add up to press, and hexavalent chromium in order to actualize the totally subjective and quantitative appraisal. Coordination steel plants use five basic materials (discus, water, fuel, and control) in the process of producing steel. It is important to note that steel can be generated at a coordinate office using press mineral as well as at an auxiliary office, which mostly uses recycled steel waste to make steel. The development industry and other building applications use a variety of rolled products (sheets, tin- and zinc-plated sheets, cold rolled groups, steel channels, sheet-metal segments, etc.) and made or drawn products (bars, wires) in conjunction with crude steel. Over time, the idea of a life cycle strategy for the supportability of products and services has received more and more attention.

Decoupling the effect of hydraulic oil contamination on the flotation performance of UG2 PGE ore and its interaction with alteration minerals

Oil contamination inadvertently arising from underground mechanised South African platinum mines is known to compromise the subsequent flotation performance. Anecdotal observations suggest that this is further exacerbated in the presence of phyllosilicate alteration minerals. Two ores of varying degrees of alteration from the Bushveld Igneous Complex were utilized in this study to investigate the effects of oil on UG2 platinum group element (PGE) ore flotation and investigate the interaction mechanisms between the oil and phyllosilicate alteration minerals. Mineralogical characterization of the ores indicated a higher percentage of the alteration phyllosilicate minerals in the altered ore (9.2 wt%) in comparison to the normal ore (5.6 wt%); with talc predominating in both ores. Baseline batch flotation test work indicated a reduction of grade with hydraulic oil addition in the normal ore (Pt by 4.5 g/t and Pd by 3.6 g/t), whereas valuable metal grades in the altered ore showed no change. In contrast to the grades, the Pt and Pd recovery dropped by 6 % and 12 %, respectively, in the altered ore floats whereas nearly constant recoveries were obtained for the normal ore as oil concentration increased. The dynamic froth stability and slurry viscosity both increased in the presence of oil and were greater in the altered ore compared to the normal ore. The observed flotation performance of the normal ore was attributed to the increasing froth stability which promoted the recovery of gangue minerals and consequent grade decrease. For the altered ore, the greater increase in the slurry pulp viscosity with oil addition was proposed to lead to poor gas dispersion and reduced interaction between bubbles and particles resulting in the reduction of recovery. The addition of sodium metasilicate successfully mitigated these effects causing a decrease in the viscosity, improvement in particle dispersion and better froth drainage. This study highlighted the potentially harmful effects of oil spillages from mechanised mining and its complex interaction with alteration minerals contained within the ore.

Recovery of Cu, Co, and Fe from Pyrite Cinder Based on Mineral Phase Reconstruction.

Pyrite cinder (PyC) containing polymetallics is difficult to use due to the low grade of metals and complex mineral phase composition, the low reutilized rate of which causes the wastage of resources. In this paper, a novel approach based on mineral phase reconstruction was proposed to recover Cu, Co, and Fe from PyC. A feasible reduction roasting process was developed for mineral phase reconstruction, followed by leaching with sulfuric acid to recover Cu and Co; finally, the leaching residue was separated by a magnetic tube to recover Fe. The maximum copper and cobalt extract rates of 86.15 and 79.61% were achieved respectively under the optimized conditions of reduction roasting for 30 min at 550 °C and 30% CO/N2 volume fraction, followed by leaching for 4 h at a liquid-solid ratio of 4:1 (mL/g), a mass concentration of 160 g/L sulfuric acid, and a temperature of 70 °C. The iron concentrate can be obtained with 63.08% Fe grade and 98.91% recovery rate by magnetic separation at a magnetic field strength of 28.26 kA/m. The mechanism analysis results of mineral phase reconstruction revealed that the primary copper sulfide in PyC was transformed into free copper oxide, combined copper oxide, and secondary copper sulfide without changing the valence state of copper by reduction roasting, resulting in a higher extraction rate of copper. Meanwhile, cobaltosic oxide and cobalt ferrite in PyC were transformed into cobalt sulfate and cobalt sulfide with the reduction of Co(III) to Co(II), improving the extraction rate of cobalt.

Comprehensive recycling of slag from the smelting of spent automotive catalysts

Spent automotive catalyst is a valuable source of platinum group metals (PGMs), making them crucial secondary resources. Currently, the main process for recovering PGMs from these catalysts is metal capture method. The smelting process would produce a significant amount of residual slags containing various components like SiO2, Al2O3, CaO, Fe2O3, Na2O, as well as high levels of heavy metals including Cr, Pb, and Ni. These slags are considered either solid waste or hazardous waste and usually disposed of in landfills, which can have detrimental effects on the environment. Furthermore, the smelting slags also contain approximately 2–5 % rare earth elements and trace amounts of precious metal elements. In this study, vacuum carbothermal reduction is employed to pretreat the smelting slags. This method not only successfully removes the heavy metal element lead, but also efficiently achieves the recovery of rare earths, and the enrichment of platinum group metals by mineral phase transformation of cerium-zirconium solid solution and in-situ iron capture. The lead removal rate exceeded 99 %, and the grade of precious metals in the enrichment process was approximately 12 times higher than the original material, with a recovery rate more than 90 %. The leaching rate of rare earths also increased from less than 50 % to more than 95 % after vacuum carbothermal reduction. The effect of vacuum carbothermal reduction pretreatment on the smelting slag phase was systematically studied, and the mechanism behind the increasing rare earth leaching rate due to this pretreatment was further analyzed.

Experimental study on high‐cycle fatigue performance of cold‐rolled steel sheet connections using self‐tapping screws and blind rivets

AbstractTo provide more suggestions for the anti‐fatigue design of cold‐formed steel, a series of high‐cycle fatigue tests are carried out on cold‐rolled steel sheets connected by self‐tapping screws and blind rivets in this paper. Subsequently, fatigue failure mode, fatigue strength, and fatigue damage are analyzed in detail. The test results show that all effective data points are below the S‐N curve of screws in the code. Meanwhile, the fatigue limit values of the fitted curves with 95% survival probability fall within the range of 0.3 to 0.67 times the specified value. Besides, the fatigue damage expansion rate of cold‐rolled steel sheets is less than the standard value. Through further discussion, it is noticed that metal grade has little influence on the fatigue performance, while thickness has a significantly positive influence on the shear resistance and fatigue performance. Moreover, the fatigue performance of the two connection types appears to be similar.

Classifying rock types by geostatistics and random forests in tandem

Rock type classification is crucial for evaluating mineral resources in ore deposits and for rock mechanics. Mineral deposits are formed in a variety of rock bodies and rock types. However, the rock type identification in drill core samples is often complicated by overprinting and weathering processes. An approach to classifying rock types from drill core data relies on whole-rock geochemical assays as features. There are few studies on rock type classification from a limited number of metal grades and dry bulk density as features. The novelty in our approach is the introduction of two sets of feature variables (proxies) at sampled data points, generated by geostatistical leave-one-out cross-validation and by kriging for removing short-scale spatial variation of the measured features. We applied our proposal to a dataset from a porphyry Cu–Au deposit in Mongolia. The model performances on a testing data subset indicate that, when the training dataset is not large, the performance of the classifier (a random forest) substantially improves by incorporating the proxy features as a complement to the original measured features. At each training data point, these proxy features throw light based on the underlying spatial data correlation structure, scales of variations, sampling design, and values of features observed at neighboring points, and show the benefits of combining geostatistics with machine learning.

Structural and Mechanical Properties of SiC-Rich By-Products of the Metal Grade Si Process

Mechanical properties of composites produced from the SiC-rich furnace slag using traditional stone and ceramic machining technologies were studied. A non-uniform mixture of coarse monocrystalline SiC grains soaked with Si-metal and glassy oxide phases represented the microstructure of dense monolithic SiC-rich samples. The fracture mechanism of coarse-grained SiC-rich composites was susceptible to the grain size/sample geometry and machining conditions yielding flexural strength in the range of 50-106 MPa and high compression strength of 750 MPa. Despite inhomogeneous macro and microstructure, mechanical and thermal properties are comparable to the traditionally produced siliconized SiSiC ceramics. It opens up the opportunity for the circular economy and value-added recycling of the Si/FeSi industries’ wastes.

Evaluation of lactate esters as novel biobased and environmentally friendly flotation frothers within PGM ore processing

As the mining industry moves towards more sustainable processing practices, the consideration of environmentally friendly reagents becomes important. Lactate esters are produced from renewable feedstock and considered green reagents because of their benign toxicological and environmental impact. Lactate esters may be considered to be suitable as flotation frothers owing to their heteropolar nature and the fact that they contain similar functional groups as commonly used industrial frothers. The most promising lactate ester, PURASOLV® BL, developed a stable froth with a lower level of entrainment than the commonly employed PPG frother, resulting in good metal recoveries and grades thereof. Utilizing lactate esters as novel green flotation frothers will attribute to the desired and mandatory shift towards greener reagents in PGM ore processing.

A Bayesian hierarchical model for the inference between metal grade with reduced variance: Case studies in porphyry Cu deposits

Ore sorting is a preconcentration technology and can dramatically reduce energy and water usage to improve the sustainability and profitability of a mining operation. In porphyry Cu deposits, Cu is the primary target, with ores usually containing secondary ‘pay’ metals such as Au, Mo and gangue elements such as Fe and As. Due to sensing technology limitations, secondary and deleterious materials vary in correlation type and strength with Cu but cannot be detected simultaneously via magnetic resonance (MR) ore sorting. Inferring the relationships between Cu and other elemental abundances is particularly critical for mineral processing.The variations in metal grade relationships occur due to the transition into different geological domains. This raises two questions - how to define these geological domains and how the metal grade relationship is influenced by these geological domains. In this paper, linear relationship is assumed between Cu grade and other metal grades. We applies a Bayesian hierarchical (partial-pooling) model to quantify the linear relationships between Cu, Au, and Fe grades from geochemical bore core data. The hierarchical model was compared with two other models - ‘complete-pooling’ model and ‘no-pooling’ model. Mining blocks were split based on spatial domain to construct hierarchical model. Geochemical bore core data records metal grades measured from laboratory assay with spatial coordinates of sample location. Two case studies from different porphyry Cu deposits were used to evaluate the performance of the hierarchical model. Markov chain Monte Carlo (MCMC) was used to sample the posterior parameters. Our results show that the Bayesian hierarchical model dramatically reduced the posterior predictive variance for metal grades regression compared to the no-pooling model. In addition, the posterior inference in the hierarchical model is insensitive to the choice of prior. The data is well-represented in the posterior which indicates a robust model. The results show that the spatial domain can be successfully utilised for metal grade regression. Uncertainty in estimating the relationship between pay metals and both secondary and gangue elements is quantified and shown to be reduced with partial-pooling. Thus, the proposed Bayesian hierarchical model can offer a reliable and stable way to monitor the relationship between metal grades for ore sorting and other mineral processing options.

Using Bayesian Neural Networks for Uncertainty Assessment of Ore Type Boundaries in Complex Geological Models

AbstractBuilding an orebody model is a key step in the design and operation of a mine because it provides the basis for follow-up mine decisions. Recently, it was shown that convolutional neural networks can successfully reproduce the manual geological interpretation of a complex ore deposit. The deep learning approach mitigates the shortcomings of a labor-intensive process that greatly limits the speed at which geological resources can be updated. However, convolutional neural network architectures lack the ability to measure the confidence of their predictions. In this study, we tried to assess the uncertainty of the boundaries of these domains so that the characterization of metal grades within them can account for this uncertainty. We explored and compared Monte Carlo Dropout and Bayesian neural networks to assess the uncertainty of deep convolutional neural network models trained to predict geological domains conditioned to drill-hole data. Monte Carlo Dropout uncertainty maps reflect the uncertainty in geological interpretations. The uncertainty is highest in areas where the interpreter/geologist had more difficulty delineating the boundaries of geological bodies. This is known as geological interpretation uncertainty. In contrast, Bayesian neural network uncertainty is visible depending on ore type frequency, complexity, and heterogeneity. Bayesian neural networks are able to better represent the uncertainty regarding the unknown. The application example here is a real case study of several ore types from a polymetallic sulfide orebody located in the south of Portugal.

The Artulândia prospect area: A newly discovered Paleoproterozoic Zn–Pb–Cu-(±Ag–Bi) VHMS mineralization in Campinorte Magmatic Arc, Central Brazil

The Artulândia prospect area is a recently-mapped, non-auriferous VHMS mineralization within Paleoproterozoic rocks in Central Brazil. The mineralization is hosted in a felsic-dominated bimodal volcano-sedimentary sequence that formed during the onset of Campinorte Magmatic Arc. The Zn–Pb–Cu-(±Ag–Bi) VHMS mineralization occurs as massive sulfide lenses and sulfide disseminations. Surrounding the sulfide lenses, two proximal hydrothermal assemblages are identified: (i) Tremolite-spessartine (±clinochlore-epidote) assemblage, associated with the sphalerite-pyrite aggregates and (ii) Clinochlore-carbonate (±tremolite-talc-serpentine) assemblage encompassing chalcopyrite, galena, and sphalerite. Besides these two assemblages, three others are considered distal to the mineralization, and interpreted to represent the stringer zone: (i) Biotite-spessartine (±chamosite-tourmaline) assemblage, with disseminated sphalerite + pyrite + galena, (ii) Biotite-sericite-carbonate (±chamosite) assemblage, with disseminated pyrite + sphalerite and (iii) Biotite-carbonate assemblage, with pyrite and traces of sphalerite intergrown with biotite lamellae. The mineralogy of the assemblages results from the Paleoproterozoic, syn-volcanic metamorphism (Neoproterozoic, Brasiliano Orogeny) of hydrothermal alteration minerals. The mineralogy and mineral chemistry data of the assemblages show that proximal assemblages formed under great influence of Fe–Mg–Ca-rich fluids. The highest grades of base metals are restricted to the sulfide lenses: Zn (1.4% wt.), Pb (1.0% wt.%), and Cu (1.8% wt.). Anomalous contents of Mo (>180 ppm), Bi (>700 ppm) and Ag (>60 g/t) occur in the proximal hydrothermal assemblages. Gold grades as high as 270 ppb are directly related to chalcopyrite-enriched zones. The δ34S measurements in pyrite vary from +8.77‰ to +10.99‰. These values are compatible with Paleoproterozoic deposits in which the isotope composition reflects a mix of seawater and leached sulfur from host rocks.

Технологические основы переработки скарновых медно-золотосодержащих руд Кыргызской Республики

Introduction. The paper studies the matters of processing of skarn copper-gold ores from a deposit in the Kyrgyz Republic. Materials and methods. As a study task, the authors performed an analysis of the material composition, including micro- and macroscopic types of analyses are presented. Results. Textural-structural analysis and mineralogical characteristics of the main ore minerals is detailed. The characteristic features of the material composition of the studied types of ores are highlighted and described. The reagent suite for processing of skarn ores has been established by means of additional feed of weakly selective depressants (Na2SiO3) and effective flotation reagents to the process, the introduction of which can significantly improve the concentrate quality. The study direction is also supplemented by the consideration and introduction of the process of mechanical activation into the process flow diagram as a reserve in increasing the grade of metals in the concentrate through the mechanical liberation of minerals by ultrafine grinding. The forms of metal loss with concentrating tailings, which are represented by wollastonite, garnet (andradite) and pyroxenes, clay-micaceous minerals, feldspars, and talc are determined. Discussion. The main losses of sulphide copper are associated with the presence of intergrowths of copper minerals with barren minerals in the samples. When evaluating copper minerals in tailings, copper is present in sulphide minerals – 79.2% and 20.8% rel. belongs to the oxide minerals. Conclusion. The paper summarizes the results of the study with the developed closed flotation flowsheet for the processing of copper-gold skarn ores, which makes it possible to obtain the flotation concentrate with grade of Cu – 25.01%, Au – 55.02g/t, Ag – 401g/t, with recovery into concentrate of Cu – 84.65%, Au – 87.94%, Ag – 89.44%. Concentrate output 2.33%. The implementation of the proposed flowsheet will ensure the achievement of planned production performance in the processing of skarn ores. Resume. At the end of the study work, the authors issued recommendations on adjusting the reagent suite with the inclusion of the weakly selective depressant – liquid glass (Na2SiO3), introducing the process of attritioning the feed of the cleaning operation (ultrafine regrinding) and considering the regularity of the phase composition of the copper minerals of skarn ore from the copper grade, providing the initial grade of copper at 0.9-1.0% in the processed ore by blending the ore feed ore to the concentrator. Suggestions for practical application and direction for future research. The materials of the paper can be useful for mining and processing enterprises when processing skarn copper-gold ores.

Atomistic structural transformation of Fe-Cr-Ni single crystal alloy under uniaxial deformation using molecular dynamics simulation

The evaluation of mechanical properties, microstructure, and phase transformation of Fe-Cr-Ni alloy under different strain rates, at temperature 300 K has been done in this investigation, using molecular dynamics simulation. These properties are of utmost importance, for the design and development of different grades of metals and alloys. In this study, a nano-size face center cubic (FCC) single crystal of Fe-Cr-Ni alloy has been selected to examine stress–strain response under various strain rates at room temperature through molecular dynamic simulation. In this simulation study, It was found that, the evolution of an alternate multilayer stack of a rectangular block of face center cubic (FCC) atoms, hexagonal close pack (HCP) rectangular block atoms and strain induced martensitic phase transformation occurred during uniaxial loading at a strain rate of 1011 s−1 at ambient temperature. It was also observed that the intersection of stacking faults is a source of dislocation. This study based on MD simulation provides an in-depth concept of the mechanical properties during mechanical and thermal processing. It also helps improve the mechanical properties of various grades of steel and other engineering materials.

Overview of the process technology for the preparation of ultrahigh purity indium required for the fabrication of indium phosphide related epitaxial structures based devices needed for advanced electronic applications

Indium, a rare metal, is created incidentally during the zinc refining process. When a zinc metal is produced, valuable elements, such as indium, are recovered and reused. The sulfide minerals, sphalerite, galena, and chalcopyrite, are all common hosts for indium metals. Indium metals of varying purities (from 99% to 99.9%) are used in many different commercial, other exclusive, specialty, dentistry, and research and development settings. In the production of indium phosphide and related select bulk single crystals, such as InP, InAs, InSb, etc., and select multilayered epitaxial material-systems based device structures, such as InGaAs/InP, InGaAsP/InP, etc., an ultrahigh purity (99.99999%) indium metal is used as one of the initial and primary input materials. light-emitting diodes, infrared detectors, lasers, and other components cannot be made without these device topologies. Triple junction solar cells made of GaInP, GaAs, and Ge with 40% conversion efficiency are being developed for use in space. Metal-organic and molecular beam epitaxial methods utilize trimethyl/triethyl-indium-epi-precursors, the high purity indium derivatives, as starting materials to develop and manufacture multilayered structures of InGaAs/InP, InGaAsP/InP, InGaN/InP AlInN, etc. The purpose of this review is to quickly touch on indium mineral sources, important uses for different indium metal grades, and the processes needed to refine, purify, and ultrahigh purify indium to higher purity levels using a zone refining–melting–leveling process, as well as impurity segregation considerations. The use of vacuum, inert gas environments, and an external electromagnetic field to efficiently segregate, levitate, stir, homogenize, and mix the molten zone/melt interface area (region) as well as purity analyses at ppb levels, class clean room, and packaging concepts were also discussed. This review also touched briefly on the use of ultrahigh purity indium in the preparation of TMIn, TEIn, and InCl precursors necessary for the growth of device structures by molecular beam, metal-organic vapor phase, atomic layer epitaxial, and chemical vapor deposition processes. Purifying and preparing polycrystalline indium to a type 7 N purity level as well as standardization and criticality testing for fine-tuning system parameters are essential parts of developing the purification process technology. It also highlights various compound semiconductors and epitaxial systems, such as high purity indium compounds, such as indium phosphide, for cutting-edge electronic applications. Material yield enhancement, impurity management (including C, O, N, and others), consistent results, impurity reduction (down to the ppb level), and class clean packaging are all active topics of research and development. There has been a rise in demand for ultrapure metals (7–10 N) with stringent purity criteria in the aerospace and defense sectors, where they are used in cutting-edge nanoelectronic applications. This literature review delves into these and related topics regarding the production of ultrahigh purity indium. The major objective of this review is to provide a concise summary of the research and development progress made toward the ultrahigh purity (7N-99.99999%) indium preparation and its epitaxial electronics application considerations as of the time of this writing.

Key factors determining the bulk ore sorting potential in a caving mine

Bulk ore sorting may add significant value to block and panel cave mines where processing feed grades are constrained by limited grade selectivity. The Cadia East gold-copper mine is a panel caving operation utilizing two different on-belt bulk ore sensors to evaluate the potential benefits of the technology. To date, there is limited reported work addressing the applicability of bulk ore sorting systems at a caving mine, where two commodities drive the economics. This indicative study is aimed at investigating the importance of various key factors on the bulk ore sorting potentials of the active and future panel caves of the Cadia East mine. Results show that for only one active cave of the mine, bulk ore sorting may be applied in the ideal scenario where grades are not affected negatively by mixing and the sorting takes place at maximum efficiency. As a general trend for all the caves, when the sorting cut-off grade is increased beyond a certain threshold, a sharp decline is observed in the sorting potentials due to the significant amounts of gold and copper deporting to the sorter rejects. In the case of a significant drop in metal prices, bulk ore sorting may only provide an opportunity to improve cave economics marginally. Results obtained by investigating the spatial change in sorting potential show that the portions of the caves with low metal grades are favourable for bulk ore sorting. In the scenario where bulk ore sorting is focused on low-grade portions, it is demonstrated that improvements in the economics of the future caves may additionally be achieved. However, as the low-grade portions represent a very small volume in the orebody, applying ore sorting on the plant conveyor may not be viable.

Recovery of base and precious metals from scrap TV boards using zig-zag air separator

Waste of Electrical and Electronic Equipments (WEEE) is one of the fastest growing waste streams in the world. The treatment of WEEE with high content of precious metals (Au in particular) has received the most attention due to their high economic potential. The development of simple, environmentally friendly and cost-effective methods for the recovery of metals from “low-value” WEEE (e.g., <100 g/t Au) is important from the circular economy perspective. In this study, the separation of base (Cu) and precious (Ag) metals from scrap TV boards (STVBs) by using a zig-zag air separator was investigated. Size-reduced scrap STVBs (-1 mm) were subjected to separation tests after the removal of the fine fraction (-0.1 mm). The sized scrap material (-1 +0.1 mm) was determined to have a metal content of 15.4% Cu, 47 g/t Ag and 0.05% Fe, with no gold. In the air separation tests, the effect of air flow rate (4-16 m/s) on the recovery of metals was studied. Increasing the air flow rate resulted in low metal recoveries with concurrent high metal grades in the concentrate. Separation efficiency (%) calculations showed that the most efficient separation is obtained at the highest air flow rate of 16 m/s. At this flow rate, 15.4% of the material was recovered in the concentrate which contains 62.3% Cu and 198 g/t Ag with recoveries of 63.3% Cu and 73.9% Ag. The findings indicated that zig-zag air separators can be used to obtain a metal-rich fraction under suitable conditions of the flow regime.

The Influence of Fluid-Exsolving Depth on Mineralization Quality: Evidence from Biotite and Zircon Mineralogy and Fluid Inclusions from the 460 Gaodi Porphyry Mo-Cu Deposit, NE China

The recently discovered 460 Gaodi porphyry Mo-Cu deposit is a sub-economic deposit characterized by low Mo-Cu grades, dispersed mineralization, and separated Mo- and Cu-ore bodies. This study aims to elucidate the factors underlying this type of sub-economic mineralization. Electron-microprobe analyses of biotite from ore-related granite porphyry yielded Ti-in-biotite crystallization temperatures of 677–734 °C (an average of 719 °C) and biotite phenocryst crystallization depths of 6.0 to 12.9 km. LA-ICP-MS analyses of zircons from the same sample revealed average zircon Ce4+/Ce3+ ratios of 299.7 and elevated zircon lg(ƒO2) ratios, with an average ΔFMQ of +6.6 ± 1.9. These discoveries suggest that the magma responsible for ore formation boasts a high degree of oxidation, yet also possesses a magma chamber located at a significant depth within the upper crust. This implies an extensive exsolving depth for fluids. Furthermore, our microthermometry analysis of fluid inclusions reveals that a portion of the fluid experiences considerable conductive cooling as it ascends along the conduit, owing to the depth of fluid exsolution. This process results in the ore fluids remaining in the liquid-only region without undergoing boiling, which is conducive to the enrichment of metals. We emphasize the fact that fluid-exsolving depth plays a critical role in determining the metal grades and economic value of a porphyry deposit by regulating the P-T evolution path of the ore fluids

In-situ texture and geochemistry of apatite from the Jinling and Zhangjiawa iron skarn deposits, eastern North China Craton: Implications for ore-forming processes and formation of high-grade ores

Apatite commonly contains abundant halogens and trace elements, which can occur in both the magmatic and hydrothermal stages, becoming favorable for recording the magmatic-hydrothermal properties and processes. Skarn-type iron deposits associated with high-Mg diorites are widespread in the Luxi Block, eastern North China Craton. Their ore-forming processes, especially how the different wallrocks (limestones and dolomites) controlled the formation of high-grade iron ores, have been poorly constrained. To unravel the mechanisms, in this contribution, in-situ textural, geochronological (U-Pb dating) and geochemical (halogens and trace elements) analyses by SEM, EPMA and LA-ICP-MS were conducted on apatite from the representative Fe skarn deposits (Jinling and Zhangjiawa deposits) in the Luxi Block. Three generations of apatite were identified in the Jinling deposit, which occur in the feldspathization (Ap1), garnet–pyroxene skarns (Ap2) and massive magnetite ores (Ap3), respectively. One generation of apatite occurring in the massive magnetite ores (Ap-3) was identified in the Zhangjiawa deposit. The Ap2 and Ap-3 apatite grains show patchy textures composed by residual bright zones (Ap2a and Ap-3a) and newly-formed grey to dark zones (Ap2b and Ap-3b), which indicate fluid metasomatism. LA-ICP-MS U-Pb dating shows that the Ap1, Ap2a and Ap3 apatite in the Jinling deposit formed at 130.4 ± 0.9 Ma (2σ), 128.5 ± 2.4 Ma and 128.3 ± 9.2 Ma, respectively, whereas the Ap-3a in the Zhangjiawa deposit formed at 128.1 ± 4.2 Ma. These ages are well consistent with the intrusive ages of the spatially associated high-Mg diorites within errors, corroborating the ore-forming fluids originating from the high-Mg rocks. All the studied apatite grains show F/Cl ratios higher than 1, especially in the early-stage apatite (e.g., 5–19 in Ap1), indicating that the originally exsolved fluids were enriched in F. The high F contents probably played a significant role in leaching Fe from the high-Mg rocks by enhancing rock porosities. The Eu/Eu* ratios of apatite increase from Ap2a to Ap3 while the Ce/Ce* ratios decrease. This suggests an increase of oxygen fugacity. The Sr concentrations in Ap3 are much higher than those in Ap-3a, correlating well with the wallrocks that limestones are developed in the former while dolomites in the latter. The above features indicate that fluid-rock interaction likely led to the increase of oxygen fugacity, which controlled the massive Fe deposition. In the Jinling deposit, the altered apatite grains (Ap2b) show much lower REE + Y but higher F contents than those of the unaltered (Ap2a), not only indicating the REEs being easily mobilized during metasomatism, but also suggesting that the high F contents likely contributed to the formation of high-grade ores by leaching additional Fe from the previously formed Fe-rich skarns. In the Zhangjiawa deposit, the altered apatite grains (Ap-3b) shows lower Cl contents than those of the unaltered (Ap-3a). This probably indicates the mixing of low-salinity fluids (e.g., recycling meteoric water), leading to the loss of Fe and thus lowering the Fe grade. The above results indicate that metasomatism is common in the skarn deposits, which can either elevate or lower the metal grade. The processes can be well recorded by apatite.

Simulating Bulk Ore Sorting Performance of a Panel Cave Mine: A Comparison between Two Approaches

Conceptual bulk ore sorting studies are essential for determining a potential improvement in mine economics before undertaking on-site sensor trials. Two approaches, block modelling and drill core compositing, are applied to simulate the bulk ore sorting performance of mining operations. While one employs the grade data of a block model, the other approach utilizes composited drill core grades. This study aimed at comparing these two approaches by estimating in-situ grade heterogeneities and simulating the bulk ore sorting performances of the currently active caves of the Cadia East panel cave mine. The results show that block modelling tends to smooth the grade variability that initially exists in the drill core grade data. Particularly in the portions of the deposit where drilling is sparse or widely spaced compared to the selected block size, block modelling leads to lower grade heterogeneity and bulk ore sorting performance estimates. However, when the drill hole data is nonrepresentative of the area of interest, block modelling can predict more realistic bulk ore sorting performances compared to drill core grades. The assessments performed with the blocks and drill core composites of various sizes showed that grade heterogeneity was adversely affected by an increased sorting scale due to averaged metal grades.

Boron nitride nanolayers in optical spectroscopic materials

Subject of study. This paper discusses nanostructures such as protective windows, plane-parallel sheets, and model plane-parallel sheets used in the development of modern fixed and mobile optical emission spectrometers and composition analyzers for rapid elemental analysis and determination of metal grades. These instruments are capable of determining the elemental compositions of pure metals and multi-component alloys within a few seconds. This paper also discusses a model depositional nanostructure: boron nitride nanotubes deposited in a single layer on an MgF2 optical-crystal substrate being used as a prototype spark-protective window in an optical emission spectrometer. Aim of study. We aim to determine whether a boron nitride nanotube nanostructure deposited on the high-wear parts of protective windows in an optical emission spectrometer can be used to stabilize instrument operations in the ultraviolet spectral region. Methods. This paper uses a density functional theory with atomic basis sets (Hartree-Fock HF/STO-3G SP). Main results. In this paper, we discuss the use of boron nitride nanotubes deposited in a single layer as a special protective coating for spectrometers. Note that deposition of boron nitride nanolayers on spectrometer components such as protective windows has practical benefits in spectroscopy because the boron nitride material used in the fabrication of washers to hold wires and rods in analyzer instruments is resistant to high temperatures. Practical significance. The solutions proposed herein are specifically relevant to optical emission spectrometers used in metal analysis and can be used to generate requirements for upgrades to improve the service life and measurement stability and provide wear-resistant protective windows for such instruments.