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This study aimed to investigate the impact of as-received biomass fly ashes (BFA) and green liquor dregs obtained from a pulp and paper plant in Brazil as substitutes for metakaolin in geopolymeric formulations. The properties of this type of waste material vary widely between different industrial plants. This study refrains from subjecting the waste materials to any form of pretreatment, taking into account their organic matter and particle size heterogeneity, requiring extensive characterization to evaluate their influence on the compressive strength, apparent open porosity, and water absorption of the geopolymeric samples. The objective was to assess their potential for upcycling purposes as an alternative to energy-intensive materials, such as ordinary Portland cement (OPC) and advanced ceramics. This potential arises from the ability of alkali-activated materials (AAM) to undergo curing at ambient temperatures, coupled with the possibility of compositions primarily derived from waste materials. To improve the sustainability of the products, the amorphous content of the raw material, which is more reactive than crystalline phases, was quantified and used as the base for mixture ratios. This approach aimed to reduce the requirement for alkaline activators, which have significant environmental impacts, while also increasing the waste content in the formulation. The incorporation of waste materials into the geopolymer matrix generally led to a reduction in the compressive strength compared to the benchmark metakaolin sample (19.4 MPa) but did not present a trend. The dregs led to values of 4.1 MPa at 25 wt% and 7.1 MPa at 50 wt%, a behavior that is somewhat counterintuitive, and BFA at 10 wt% presented 5.7 MPa. Nevertheless, the apparent open porosity remained at high levels for all the samples, close to 50%, and the compressive strength of most of them was over the values obtained for the metakaolin-only samples with mixture ratios calculated from the total composition instead of the amorphous composition. The decrease in strength and the increase in porosity were attributed to the specific characteristics of the waste materials, such as their high crystallinity, presence of organic matter, heterogeneous particle composition, and size. Overall, this study provides insight into the variations in geopolymerization based on the bulk and amorphous content of the aluminosilicate sources and how the characteristics of the waste materials influence the geopolymer matrix. It also highlights how calculating mixture ratios based on the amorphous composition improves the possibility of waste valorization through alkali activation. Additionally, it suggests that BFA and dregs might be effectively utilized in applications other than OPC substitution, such as adsorption, filtration, and catalysis. [ABSTRACT FROM AUTHOR]

The ionic rare earth (RE) ore body undergoes particle transport and pore structure change during the leaching process, resulting in "uneven percolation, preferential channel, leaching blind area," and other problems, leading to structural changes in the ore body, low leaching efficiency, and waste of resources. The unsaturated infiltration process is also the key stage that causes these problems. The initial pore structure evolution of the ore body plays a decisive role in the permeability coefficient of the ore body, and the direct influencing factor of the permeability coefficient is the distribution of the pore radius. We carried out research through indoor simulated leaching, the filter paper method for determining matrix suction, and nuclear magnetic resonance (NMR) testing. An ionic rare earth ore soil-water characteristic curve within a large matrix suction range was obtained by the filter paper method. With the increase in volumetric water content, the matrix suction presents a sharp downward trend. When the volumetric water content is less than 20%, this rule is particularly obvious. With the increase in matrix suction, the thickness of the adsorbed water film on the particle surface and pore radius show a decreasing power function trend. Under percolation, the porosity of an ionic rare earth ore sample tends to increase linearly with the increase in volumetric water content during the process from non-saturation to saturation; the porosity of a saturated ore sample after seepage expanded by 17.5 times compared to that of an unsaturated ore sample before seepage. The change rule of the internal microstructure of the ore sample is reflected in the gradual disappearance of micro pores and the gradual formation of small, medium, large, and mega pores, which shows a gradual increase trend. In the pore radius distribution, the more large and medium pores, the larger the permeability coefficient; the more micro and small pores, the smaller the permeability coefficient. For some ore bodies with poor permeability, the ore body is infiltrated with clear water under small water pressure before leaching with a leaching solution, which can improve the permeability of the ore body, effectively improve the efficiency of rare earth leaching, and increase the economic benefits. [ABSTRACT FROM AUTHOR]

Current literature dealing with the theory of sampling process flows is limited in scope, a situation addressed by papers presented at conferences by the author. This paper provides a summary of methods to quantify process sampling variance in a sound statistical manner. Two methods of calculation of the process sampling variance are presented here with models for robust estimation of the process covariance/variogram. The strategies for process sampling to acquire the data for process characterisation are described. The method for process characterisation can be based on special sampling campaigns, on the analysis of on-line measurement data, or on the analysis of historical data, which may be based on composite samples, such as shift samples. These scenarios are all dealt with as well as methods based on analysis of process dynamics. The latter analysis demonstrates that use of covariance functions drawn from geostatistical practice can be inappropriate for process analysis. The work is supported with plant data examples and quantitative analyses of process conditions. [ABSTRACT FROM AUTHOR]

The edge detection method based on the magnetic gradient tensor data plays an important role in magnetic exploration because it is free from geomagnetic interference and contains more abundant information. This paper proposes a new anomaly edge detection method using the magnetic gradient tensor components. The model is established to compare with other methods, such as directional total horizontal derivative (THDz), analytical signal (AS), tilt angle, theta map, and so on, under conditions of vertical magnetization, oblique magnetization, and noise interference. Through the study of the anomaly distribution of the rectangular model, it is observed that the edge detection method proposed in this paper is nearly impervious to noise interference, exhibits strong anti-interference capabilities, delivers a high-quality boundary identification effect, and provides greater accuracy in anomaly edges with minimal error. When multiple anomalous bodies are present, the edge detection results are less susceptible to interference from each other, resulting in higher resolution. The efficiency of the algorithm is demonstrated by real magnetic data from some study areas in Jiangxi Province, China. The experimental results show that the proposed method is more precise and accurate than the total horizontal derivative, analytical signal, tilt angle, and theta map methods. [ABSTRACT FROM AUTHOR]

Travertine and calcareous tufa are types of continental carbonates that form in subaerial environments near groundwater seepages, springs, and rivers. These deposits exist on all continents and can provide valuable information about past climates, environmental changes, and geological activity. A recent special issue of the journal Minerals focuses on the geochemistry of travertines and calcareous tufas, with contributions from researchers studying deposits in various locations around the world. The articles cover topics such as the formation processes, depositional environments, and diagenesis of these carbonate deposits, as well as their use as paleoclimate records and indicators of geothermal resources. The studies employ a multidisciplinary approach, combining techniques such as geochemistry, mineralogy, petrography, and isotopic analysis to gain a comprehensive understanding of these complex systems. Overall, the contributions highlight the importance of geochemical tracers in enhancing our knowledge of travertines and calcareous tufas. [Extracted from the article]

In recent years, the Mineral Liberation Analyser (MLA) has played a pivotal role in analysing respirable and inhalable ambient air samples collected on filters from both underground coal and metalliferous mines. Leveraging backscattered electron (BSE) image analysis and X-ray mineral identification, the MLA offers automated quantitative mineral characterization. The escalating prevalence and severity of mine dust lung diseases, particularly among young miners, have reignited interest in comprehensively understanding the dust's characterization, encompassing mineralogy, particle size, and shape. Merely measuring total respirable dust exposure and its duration based on gravimetrically determined weight is no longer deemed sufficient in addressing the evolving landscape of occupational health challenges in mining environments. Since the publication of previous studies, efforts have been dedicated to refining the Mineral Liberation Analyser (MLA) methodology for respirable dust sampling. This refinement, discussed in detail in this paper, encompasses various enhancements, such as the implementation of data checks to identify carbon contamination, backscattered electron (BSE) drift, and the misclassification of X-ray spectra. Additionally, an examination of sampling efficiency led to the exploration of using smaller samples as an alternative to the time-intensive analysis of entire filters. Furthermore, this paper presents a reanalysis of paired filter sample sets previously reported using the Sarver Group Methodology. These samples are subjected to analysis using the Mineral Liberation Analyser, providing a more detailed illustration of the outputs derived from the updated methodology and compared to previously published MLA data. [ABSTRACT FROM AUTHOR]

Incinerated ash with a relatively high Ca content, paper sludge ash, was converted to zeolitic materials with high cation-exchange capacities (CECs) by aging at 80 °C in NaOH solution via step-wise acid leaching with HCl to reduce the ash Ca content. The extraction of Ca, Mg, Si, and Al from the ash into the acid solutions during leaching and the products obtained from the leached ash by reaction with an alkali were examined. The contents of Ca and Mg in the ash were more easily extracted from the ash than those of Si and Al in the initial leaching. The leachant pH decreased with increasing numbers of leaching steps, and the amounts of Si, Al, and Ca extracted from the ash increased as a result of the dissolution of gehlenite (Ca2Al2SiO7), one of the main minerals in the ash. Zeolites A and P were synthesized from the leached ashes, and hydroxysodalite was synthesized from the raw ash. With increasing numbers of leaching steps of the ash, the obtained product contained lower released Ca, whereas the product contained higher released Na and has higher CEC, depending on the zeolite phases in the product. The product with the highest CEC was synthesized from third-leached ash, and its CEC was 1.5 mmol/g, which is about four times higher than that of the raw ash (0.4 mmol/g). [ABSTRACT FROM AUTHOR]

Seismic exploration has caught widespread attention in metal ore exploration due to its higher resolution. However, the presence of topography and complex underground structures in metal ore exploration complicates seismic records. Therefore, it is essential to apply a numerical simulation method suitable for metal ore exploration to study the propagation law of seismic waves in shallow and ore-forming zones, providing reliable theoretical support for multi-component seismic techniques. In particular, the presence of topography generates strong-amplitude surface waves, scattered waves, and converted waves, which consistently distort seismic records and affect the imaging accuracy of the metallogenic belts. Additionally, the propagation of seismic waves is also affected by the anisotropy and viscoelasticity of the underground medium. This paper proposes an elastic wave finite-difference numerical simulation method suitable for irregularly topographical and complex medium conditions, named the comprehensive parameter correction method, which implements a free-surface boundary condition based on the concept of medium averaging. It is algorithmically simple and implies no additional computational costs. Meanwhile, the results obtained by this method are highly consistent with those of the spectral element method, demonstrating its accuracy. By presenting several numerical simulation cases and illustrating the impact of topography and medium conditions on seismic records, this paper demonstrates the necessity of considering irregularly topographical and complex medium conditions in metal ore exploration. In conclusion, the numerical simulation method we propose provides a solid theoretical foundation for the application of seismic exploration methods in metal ore exploration. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the implementation of artificial self-awareness mechanisms and self-reflection abilities in deep neural networks. While the current limitations of research prevent achieving cognitive capabilities on par with natural biological entities, the incorporation of basic self-awareness and self-reflection mechanisms in deep learning architectures offers substantial advantages in tackling specific problems across various scientific fields, including geosciences. In the first section, we outline the foundational architecture of our deep learning approach termed Self-Aware Learning (SAL). The subsequent part of the paper highlights the practical benefits of this machine learning methodology through synthetic tests and applications addressed to automatic classification and image analysis of real petrological data sets. We show how Self-Aware Learning allows enhanced accuracy, reduced overfitting problems, and improved performances compared to other existing methods. [ABSTRACT FROM AUTHOR]

Ion-adsorption-type rare earth ores (IRE-ores) are a vital source of rare earth elements globally. The percolation properties of the ore body significantly determine the ease of rare earth extraction using in situ leaching processes. This paper investigates the interactions among clay particles in ion-adsorption-type rare earth ores within aqueous solutions, utilizing methods such as mineral particle aggregation and settling and acid–base adsorption on mineral surfaces. Based on these analyses, this paper elucidates the influence of solution properties on the percolation process of ion-type rare earth ores during leaching. The results indicate that the electrostatic attraction between minerals in aqueous solutions is pronounced, enhancing the interaction and resulting in a notable instability of the aggregates. The aggregation of minerals impacts the viscous effect of water bound to the mineral surface on the solution, thereby affecting the percolation rate. Extremely low concentrations of SO42− and CH3COO− can act as surface modifiers, reducing the electrostatic attraction between particles and consequently increasing the leaching percolation rate. [ABSTRACT FROM AUTHOR]

This document is an editorial for a special issue of the journal Minerals titled "Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives." The editorial highlights the importance of the ecological transition in aligning human activities with the global ecosystem to address challenges such as climate change and social disparities. It discusses the paradoxical nature of the ecological transition, which increases the demand for minerals while aiming to move away from fossil fuels. The special issue includes papers that explore various aspects of sustainable mining, including resource characterization, environmental impact assessment, waste recycling, and the development of new solutions. The editorial also acknowledges the need for diverse expertise and adherence to environmental and social governance standards in sustainable mining practices. [Extracted from the article]

With the massive use of lithium-ion batteries in electric vehicles and energy storage, the environmental and resource problems faced by used lithium-ion batteries are becoming more and more prominent. In order to better resource utilization and environmental protection, this paper employs bibliometric and data analysis methods to explore publications related to waste lithium-ion battery recycling from 1984 to 2021. The Web of Science core set from the SCIE online database was used for this article. These findings demonstrate a considerable increase trend in the number of publications published in the subject of recycling used lithium-ion batteries, with a natural-sciences-centric focus. Argonne National Lab, Chinese Academy of Sciences, and China Academic and Scientific Research Center are the top three institutions in terms of quantity of papers published. The affiliated journals corresponding to these three institutions also have high impact factors, which are 106.47, 44.85, and 58.69, respectively. In comparison to comparable institutes in other nations, the American Argonne National Laboratory supports 223 research articles in this area. China and the US make up the majority of the research's funding. The two key aspects of current lithium-ion battery recycling research are material structure research and environmentally friendly recycling. Nevertheless, high-capacity lithium-ion batteries, waste lithium-ion integrated structures, and gentle recycling of spent lithium-ion batteries will be the major aspects of study in the future. It is hoped that the above analysis can bring new ideas and methods to the field of waste lithium-ion battery recycling and provide a basis for the subsequent research and application of waste lithium-ion battery recycling. [ABSTRACT FROM AUTHOR]

Microwave-assisted rock breaking is a new and promising technology for the tunneling and drilling industry. Minerals in rocks have an important influence on the effect of microwave-assisted rock breaking. In this paper, common minerals in rocks such as potash feldspar (hereafter referred to as K-feldspar), calcite and pyroxene were selected as samples, and a lot of microwave irradiation tests were carried out by using a hamilab-v1500 microwave oven. The mass, strength and microstructure of the rock samples were tested before and after microwave irradiation. The change law of the mineral mass, strength and microstructure with regard to temperature was analyzed, and the influence mechanism was discussed. The results show that the strength of K-feldspar increases from 20 °C to 400 °C but decreases significantly when it is higher than 400 °C; the strength of pyroxene increases from 20 °C to 600 °C but decreases when it is higher than 600 °C; the strength of calcite decreases with the increase in temperature. As for the weakening pattern, pyroxene shows drawstring, step and flow with the increase in temperature, but K-feldspar and calcite show that failure occurs along the cleavage plane of the crystal structure. The higher the temperature of microwave irradiation, the finer the pattern at the fractured zone is, and the more fragmented it becomes; the loss of mineral mass increases with the increase in the temperature of microwave irradiation. [ABSTRACT FROM AUTHOR]

This paper presents simulations of different concentration plants that use Inert Construction and Demolition Waste as feed to generate coarse aggregates from old concretes. Different feed materials were studied: CDW generated in Spain; low-strength concretes, C16/20, which are ordinary concrete used in civil construction; and high-strength concretes, C50/60, from specific demolitions, such as old viaducts and bridges. Granulometric and densimetric analyses were performed, and the composition of the granulometric fractions of the proposed concretes were analyzed based on previous studies carried out, to understand the materials that can be recovered and considered for reinvestment in the market. Investment analysis considering the CAPEX, OPEX, revenue, IRR, MIRR, NPV, and DPP of the different concentrating plants with varying streams of concentration to recover the materials of interest (coarse aggregates) are presented and discussed. The results of the analyses indicate greater viability in plants that use mobile plants and the use of water jigs. [ABSTRACT FROM AUTHOR]

The awareness of tailings dam safety monitoring has widened due to the recent disasters caused by failures of such structures. The failure rate of tailings dams worldwide (i.e., the percentage of failed dams out of total) is estimated at 1.2%, compared to the 0.01% rate for traditional water dams. Most of the tailings dam monitoring guidelines suggest that the owner develops a robust surveillance program to detect possible indicators of potential failures. This paper presents a thorough review of major guidelines on tailings storage facility (TSF) monitoring and surveillance, the visual parameters to be monitored, as well as good practice in the development of monitoring systems. This paper reviews the recent literature with an emphasis on the development of monitoring systems utilizing sensors, unmanned aerial vehicles (UAVs), and satellite images that may be considered as supplementary guarantees against failure events. [ABSTRACT FROM AUTHOR]

This paper explores the efficiency and potential of indirect freeze crystallization (IFC) as a valuable resource-recovery technology in wastewater treatment, particularly focusing on acid mine water and hazardous material wastewater-treatment plants. Wastewater treatment poses challenges to recovering valuable resources effectively, enforcing the need for sustainable and resource-efficient technologies like freeze crystallization. Through a thorough examination of IFC principles and mechanisms, this paper aims to highlight its applications, advantages, and limitations. The investigation includes a comprehensive literature review and detailed methodology from one of the IFC pilot plants, as well as a critical analysis of the environmental and economic implications of IFC. By addressing scaling challenges in reverse osmosis and proposing an environmentally friendly brine disposal method through IFC, this paper contributes to reducing the environmental footprint associated with wastewater treatment. Additionally, this paper highlights the importance of extracting valuable resources from highly saline water and emphasises the potential economic and environmental benefits of resource recovery, particularly focusing on the promising technology of IFC. [ABSTRACT FROM AUTHOR]

The study of process mineralogy plays a very important role in the field of mineral processing and metallurgy, in which the measurement of mineral-embedded particle size is one of the main research areas. The manual measurement method using a microscope has many problems, such as heavy workload and low measurement accuracy. In order to solve this problem, this paper proposes a Gaussian mixture model based on an expectation maximization (EM) algorithm to measure the embedded particle sizes of minerals of polished metal sections. Experiments are here performed on the polished section images of ilmenite and pyrite, and we compared the results with a microscope. The experimental results show that the proposed method has higher precision and accuracy in measuring the embedded particle sizes of metal minerals. [ABSTRACT FROM AUTHOR]

Kaolin-group minerals occur in nature as the result of high-sulfidation acid sulfate, sulfur-poor HCl-, HF- and H2CO3-rich acidic fluid-related hydrothermal alterations and in situ geochemical weathering. These minerals possess different crystallographic and chemical properties that determine their application areas, mainly in the ceramic and paper industries, and as nanocomposite materials. The physicochemical properties of hydrothermal kaolin deposits are the result of the type of parent rock, the effect of the regional tectonism-associated magmatism, and the chemical features of hydrothermal fluids that interact with the deep basement rocks. However, understanding these geothermal systems is one of the most challenging issues due to the rich mineralogical assemblages, complex geochemistry and isotopic data of hydrothermal alteration zones. This study evaluates the formation of hydrothermal-origin kaolin-group minerals by considering their characteristics of hydrothermal alteration, isotopic compositions and differences in characteristic properties of low- and high-sulfidation occurrences; this paper also addresses mineralogical and structural differences between hypogene and supergene kaolin formations, and kaolin–alunite–pyrophyllite association, and it provides examples of worldwide occurrences. The study of the mineralogical assemblages, geochemistry and isotopic data of the hydrothermal alteration zones is one of the most challenging subjects in terms of gaining a detailed understanding of the geothermal systems. Silicification processes are subsequent to late-stage alteration after the completion of kaolinization processes, erasing existing hydrothermal mineralogical and geochemical traces and making interpretation difficult. In the early stages involving magmatic–hydrothermal-origin acidic geothermal fluids, the latter comes from the disproportionation of SO2 (+H2O) and H2S oxidation to H2SO4 in hydrothermal environments. In the later stages, due to spatial and temporal changes over time in the chemistry of geothermal fluids, the system comes to have a more alkali–chloride composition, with neutral pH waters frequently saturated with amorphous silica which characteristically precipitate as siliceous sinter deposits containing large amounts of opal-A. [ABSTRACT FROM AUTHOR]

The pre-Jurassic in the north depression of the Tuha depression is the most favorable replacement strata to obtain new reserves in the Turpan–Hami Basin. (Pre-Jurassic, in this paper, refers to the Permian and Triassic.) The main source rocks are the Taodonggou Group, of which the burial history and hydrocarbon generation potential remain unconfirmed. The investigation of the burial and thermal history is vital for the basin analysis and hydrocarbon exploration. Therefore, in this paper, by using the acoustic time difference method, vitrinite reflectance method, stratigraphic trend method and PetroMod-1D software, the differential characteristics of denudation thickness, burial history and thermal evolution history of different tectonic units in different periods of Taibei Sag in the Turpan–Hami basin are studied, and their influence on the petroleum system is analyzed, and then the zones with exploration potential are optimized. The results show that the Taibei Sag has experienced multiple tectonic uplift events. The Late Indosinian movement has profound effects on the Taodonggou Group source rocks. The rather large uplift amplitude postpones the maturation of source rocks. In addition, the Turpan–Hami Basin is a typical cold basin. Therefore, the thermal maturity of the source rocks is relatively low, with respect to the relatively deep burial. The thermal histories of the different sub-sags in the study area are slightly differentiated from each other. The Taodonggou Group source rocks in the Taibei Sag generally became mature during the Mid–Late Jurassic epoch, except for those in the Central–Southern Shanbei sub-sag, represented by Well LT-1, which reached the mature stage during the Late Triassic epoch. The study area has well-developed reservoir rocks, and effective reservoir bodies are formed in the slope zone and near the Tainan Sag, due to the higher porosity and permeability of reservoir rocks. The statistics related to the faults and an analysis of the structural styles of oil reservoirs indicate that the structural slope and anticline of the Huobei, Lianbei and Shanbei sub-sags are favorable for increasing reserves and production of hydrocarbons. [ABSTRACT FROM AUTHOR]

With the rapid development of modern geochemical analysis techniques, massive volumes of data are being generated from various sources and forms, and geochemical data acquisition and analysis have become important tools for studying geochemical processes and environmental changes. However, geochemical data have high-dimensional, nonlinear characteristics, and traditional geochemical data analysis methods have struggled to meet the demands of modern science. Nowadays, the development of big data and artificial intelligence technologies has provided new ideas and methods for geochemical data analysis. However, geochemical research involves numerous fields such as petrology, ore deposit, mineralogy, and others, each with its specific research methods and objectives, making it difficult to strike a balance between depth and breadth of investigation. Additionally, due to limitations in data sources and collection methods, existing studies often focus on a specific discipline or issue, lacking a comprehensive understanding of the bigger picture and foresight for the future. To assist geochemists in identifying research hotspots in the field and exploring solutions to the aforementioned issues, this article comprehensively reviews related studies in recent years, elaborates on the necessity and challenges of combining geochemistry and artificial intelligence, and analyzes the characteristics and research hotspots of the global collaboration network in this field. The study reveals that the investigation into artificial intelligence techniques to address geochemical issues is progressing swiftly. Joint research papers serve as the primary means of contact within a worldwide collaborative network. The primary areas of focus in the ongoing research on the integration of geochemistry and artificial intelligence include methodologies for analyzing geochemical data, environmental modifications, and mineral prospectivity mapping. Geochemical data analysis is currently a significant focus of research, encompassing a range of methods including machine learning and deep learning. Predicting mineral resources for deep space, deep Earth, and deep sea is also a pressing topic in contemporary research. This paper explores the factors driving research interest and future trends, identifies current research challenges, and considers opportunities for future research. [ABSTRACT FROM AUTHOR]

Using alternative materials such as residual products from other industries to mitigate the negative effects of acid rock drainage would simultaneously solve two environmental problems. The main residual product still landfilled by sulphate paper mills is the alkaline material green liquor dregs (GLD). A physical, mineralogical and chemical characterization of four batches of GLD was carried out to evaluate the potential to use it as a sealing layer in the construction of dry covers on sulphide-bearing mine waste. GLD has relatively low hydraulic conductivity (10-8 to 10-9 m/s), a high water retention capacity (WRC) and small particle size. Whilst the chemical and mineralogical composition varied between the different batches, these variations were not reflected in properties such as hydraulic conductivity and WRC. Due to relatively low trace element concentrations, leaching of contaminants from the GLD is not a concern for the environment. However, GLD is a sticky material, difficult to apply on mine waste deposits and the shear strength is insufficient for engineering applications. Therefore, improving the mechanical properties is necessary. In addition, GLD has a high buffering capacity indicating that it could act as an alkaline barrier. Once engineering technicalities have been overcome, the long-term effectiveness of GLD should be studied, especially the effect of aging and how the sealing layer would be engineered in respect to topography and climatic conditions. [ABSTRACT FROM AUTHOR]

In this paper, we have synthesized the information derived from more than 20 papers and PhD theses on the anisotropy of the magnetic susceptibility (AMS) of 19 Variscan granite plutons, spanning the period between 320 Ma and 296 Ma. The AMS data are obtained from 876 sampling sites with more than 7080 AMS measurements and a re-interpretation is proposed. The studied granites exhibit a magnetic susceptibility (Km) ranging from 30 to 10,436 × 10−6 SI units. Most granites typically exhibit Km values below 1000 × 10−6 SI, indicative of paramagnetic behavior. Biotite serves as the main carrier of iron (Fe), emphasizing the reduced conditions prevalent during the formation of granite melts in the Variscan orogeny. The AMS fabrics of the studied granite plutons record the magma strain, expressing the chronologic evolution of the stress field during the orogeny. This chronologic approach highlights the magmatic events between around 330 and 315 Ma, occurring in an extensional regime, in which the Borralha pluton is an example of a suite that recorded this extensional AMS fabric. Plutons with ages between 315 and 305 Ma show AMS fabrics, pointing out their emplacement in a compressional tectonic regime related to the Variscan collision. The plutons, younger than 305 Ma, record AMS fabrics indicating that the tectonic setting for emplacement changes from a wrench regime to an extensional one at the end of the collision stage. This is evident as there is a chronological overlap between the granites that exhibit AMS fabrics indicating extension and the ones that have AMS fabrics indicating a wrench regime. [ABSTRACT FROM AUTHOR]

In recent years, mine site closure and rehabilitation have emerged as significant global challenges. The escalating number of abandoned mines, exemplified by over 60,000 in Australia in 2017, underscores the urgency. Growing public concerns and governmental focus on environmental issues are now jeopardising sustainable mining practices. This paper assesses the role of unmanned aerial vehicles (UAVs) in mine closure, exploring sensor technology, artificial intelligence (AI), and mixed reality (MR) applications. Prior research validates UAV efficacy in mining, introducing various deployable sensors. Some studies delve into AI's use for UAV data analysis, but a comprehensive review integrating AI algorithms with MR methods for mine rehabilitation is lacking. The paper discusses data acquisition methods, repeatability, and barriers toward fully autonomous monitoring systems for mine closure projects. While UAVs prove adaptable with various sensors, constraints such as battery life and payload capacity impact effectiveness. Although UAVs hold potential for AI testing in mine closure studies, these applications have been overlooked. AI algorithms are pivotal for creating autonomous systems, reducing operator intervention. Moreover, MR's significance in mine closure is evident, emphasising its application in the mining industry. Ultimately, a hybrid UAV–AI–MR technology is not only viable but essential for achieving successful mine closure and sustainable mining practices in the future. [ABSTRACT FROM AUTHOR]

The accumulation of carbon dioxide in the atmosphere due to fossil fuel burning and deforestation has caused global warming and an increase in extreme weather events. To complement the shift towards clean energy, it is crucial to adopt methods for carbon dioxide removal, known as negative emission technologies. Enhanced weathering is one such approach that involves accelerating the natural process of rock weathering by spreading finely ground rocks over large areas, such as agricultural land or coastal areas. This exploratory review paper provides an overview of the fundamental mechanisms behind enhanced weathering, and outlines the techniques for its implementation. The environmental benefits of enhanced weathering are highlighted, including carbon dioxide removal, and improvement of soil fertility. Furthermore, potential impacts on ecosystems and biodiversity are examined, along with the effects on water, soil and air quality. The paper also considers the risks and challenges associated with large-scale implementation and long-term stability of enhanced weathering. Additionally, the integration of enhanced weathering with Sustainable Development Goals is explored, along with the potential co-benefits and trade-offs with other sustainability objectives. To conclude, this exploratory review paper summarizes the key findings and proposes avenues for further research in this field of enhanced weathering. [ABSTRACT FROM AUTHOR]

Super-reduced phases (SRPs), such as silicon carbide (SiC) and metal silicides, have increasingly been reported in various geological environments. However, their origin remains controversial. SRP inclusions (e.g., metal silicides and metallic silicon (Si0)) within SiC are commonly believed to indicate a natural origin. Here, we identified an unusual SRP assemblage (SiC, (Fe,Ni)Si2, and Si0) in situ in an H5-type Jingshan ordinary chondrite. Simultaneously, our analysis showed that the SiC abrasives contain (Fe,Ni)Si2 and Si0 inclusions. Other inclusions in the artificial SiC were similar to those in natural SiC (moissanite) reported in reference data, including diverse metal silicides (e.g., FeSi, FeSi2, Fe3Si7, and Fe5Si3), as well as a light rare earth element-enriched SiO phase and Fe-Mn-Cr alloys. These inclusions were produced by the in situ reduction of silica and the interaction between Si-containing coke and hot metals during the synthesis of the SiC abrasives. The results demonstrate that the SRP assemblage in the Jingshan chondrite originates from abrasive contamination and that the SRP inclusions (with a low content of Ca, Al, Ti, and Zr) cannot be used as a conclusive indicator for natural SiC. Additionally, the morphologies, biaxiality, and polytypes (determined by Raman spectroscopy) of SiC abrasives bear resemblance to those reported for natural SiC, and caution must be exercised when identifying the origin of SRP in samples processed by conventional methods using SiC abrasives. At the end of this paper, we propose more direct and reliable methods for distinguishing between natural and synthetic SiC. [ABSTRACT FROM AUTHOR]

Oxide copper minerals are commonly extracted via acidic leaching, using acids such as H2SO4, HCl, or HNO3. These strong acids are the most widely used because of their high dissolution kinetics. However, their main concern is the high acid consumption because copper oxide deposits contain large amounts of acid-consuming gangue. This paper proposes using an alternative aqueous alkaline monosodium glutamate (MSG) system to leach copper oxide minerals. Tenorite (CuO) was used as the copper oxide mineral under study. The influence of process variables (such as temperature and glutamate concentration) and kinetics of this system on copper leaching from tenorite were studied. The results showed that temperature has a significant effect on copper dissolution rates. Increased temperature from 15 °C to 60 °C enhanced the copper extraction from 9.1% to 97.7% after 2 h. Leaching kinetics were analyzed using the shrinking core model (SCM) under various conditions, indicating that the leaching rate presented a mixed control. This method, however, fails to describe leaching for broad particle sizes due to its requirement for single-sized solid grains. This study demonstrated that a large particle size distribution in tenorite supported a successful extension of the SCM for leaching it from mixed glutamate solutions. The activation energy for the 15–60 °C temperature range was calculated to be 102.6 kJ/mol for the chemical control. [ABSTRACT FROM AUTHOR]

The dynamics of milling circuits, particularly those involving Semi-Autogenous Grinding (SAG) mills, are not adequately studied, despite their critical importance in mineral processing. This paper aims to investigate the dynamic behavior of an SAG mill pebble recycling circuit under varying feed ore conditions, focusing on both uncontrollable parameters (such as ore hardness) and controllable parameters (including circuit layout and pebble crusher configurations). The study is carried out with Simulink dynamic simulations. Our findings reveal several key insights. Firstly, plant designs based solely on static simulations may not be adequate for large or complex circuits, as they fail to account for the dynamic nature of milling processes. Second, incorporating stockpiles after pebble crushing can effectively mitigate the impact of dynamic fluctuations, leading to more stable circuit performance. Third, different circuit layouts can facilitate easier maintenance and operational flexibility. Notably, finer pebble crushing can enhance circuit throughput by 5% to 10%. [ABSTRACT FROM AUTHOR]

The airborne electromagnetic system MobileMT exploits natural fields in a broadband frequency range with offset measurements of magnetic and electric field variations. It was introduced in 2018 and has since been developed in various configurations, each tailored to meet the demands of different exploration tasks, varied terrains, and geoelectrical conditions and support time-domain data with controlled primary field sources. There are four distinct airborne systems: the original MobileMT; the lighter configuration, MobileMTm; the configuration for a drone carrier, MobileMTd; and the innovative time-domain AFMAG hybrid, TargetEM. The paper describes the technical features of each system, their differences and inherent strengths, the optimal usage conditions, and insights into their applications under different conditions across various exploration tasks. Several field case studies are provided to support the natural field electromagnetics capabilities of recovering geological structures in a wide depth range, beginning from the near surface, and address the impact of parasitic IP effects on time-domain data. [ABSTRACT FROM AUTHOR]

The X-type strike-slip fault system and weathering crust karst fracture-cave and channel reservoirs were developed in the Halahatang area of the northern Tarim Basin. However, the relationship between the reservoir and the strike-slip fault remains controversial. Based on the core data, and taking an NE-striking strike-slip fault as an example, this paper dissects the karst reservoir from wells along the strike-slip fault damage zone and analyzes the control of scales, properties, and segmentation styles of strike-slip faults on karst reservoirs. The results show that (1) the scale of the strike-slip fault controls the distribution of the reservoir—the wider the fault damage zone, the wider the fracture-cave reservoirs; (2) the transtensional segments of the strike-slip fault are more likely to produce karstification, and the buried-hill area and the interbedded area are controlled by different hydrodynamic conditions to form different types of karst reservoirs; (3) six different parts of the strike-slip fault are conducive to the formation scale of fault fracture zones. This research provides new insight into recognizing karst reservoirs within strike-slip fault damage zones, which can be further applied to predict karst reservoirs controlled by strike-slip faults. [ABSTRACT FROM AUTHOR]

The Xujiashan Sb deposit located at the Mufushan fold thrust belt of the Yangtze block is one of the most important Sb deposits in this district. Stibnite in this deposit contains high and various contents of Se, but research on the distribution and enrichment of Se in stibnite remains limited. This paper conducts geochemical composition, C-H-O isotopic composition, and scanning electron microscopy morphology of the Xujiashan deposit to discuss the sources of ore-forming materials and fluid, as well as the distribution and enrichment mechanisms of selenium in stibnite. The results showed that the ores have trace element compositions comparable with the wall rocks, and Sb and Se contents are significantly higher than the average carbonate rocks. The δ13CPDB values of calcite and quartz range from −12.8‰ to 5.5‰, the δ18OSMOW values range from 20.4‰ to 24‰, and the δDV-SMOW values range from −57.8‰ to −86.9‰. Trace element and isotope compositions indicate that the ore-forming materials were mainly derived from the wall rocks (sedimentary–metamorphic rocks) that S, Se, and Sb dissolved during fluid–rock interactions. The ore-forming fluids were metamorphic water produced by metamorphism, which had experienced multistage mixing with meteoric water and organic-rich fluids. Selenium substitutes for sulfur in the stibnite crystal lattice, causing rhythmically distributed Se contents in stibnite, which resulted from multistage physicochemical changes in ore-forming fluids during crystallization. The varied patterns of Se contents are the result of different cross-sections of the stibnite. [ABSTRACT FROM AUTHOR]

The effective separation of ore is based on two fundamental processes: liberation and separability. Liberation involves the reduction of size, yielding smaller particles with enhanced compositional homogeneity. Understanding liberation requires an understanding of rock breakage, as it impacts mineral liberation and helps identify ores suitable for pre-concentration. Non-random breakage, influenced by textural and mineral properties, introduces heterogeneity in mineral distribution across size fractions. Physical attributes, including ore and gangue mineralogy and texture, influence fractionation tendencies during breakage. Notably, the presence of mineralization in veins substantially assists early-stage liberation in mineral processing. The aim of this study is to develop a methodology that allows the prediction of natural fractionation tendencies based on geological, mineralogical, and textural data using Discrete Element Method (DEM) modeling. DEM simulations provide insights into granular material behavior, capturing phenomena such as crack initiation and propagation. The use of DEM, particularly with models such as the Flat Joint Model (FJM), enhances our understanding of rock damage mechanisms. In this paper, DEM is used to predict preferential grade by size deportment, and a numerical model is developed to reflect grade distributions across size fractions. A fragmentation analysis is conducted after rock breakage simulations using DEM to analyze the fragment sizes and grades and calculate the Response Rankings of synthetic specimens. [ABSTRACT FROM AUTHOR]

Rock fragmentation is an important evaluation indicator for field blasting operations. This paper applies a deep learning-based method, the Segment Anything Model (SAM), to automatically segment rock fragments. To review the SAM's segmentation performance, 83 images of rock fragment collected from the mine site were used as the test dataset. Pixel-level accuracy (PA), intersection over union (IOU), and dice coefficient (Dice) were employed to evaluate the model pixel-level segmentation performance. The results showed that the SAM exhibited excellent segmentation performance on the test data (PA = 94.5%, IOU = 94.4%, Dice = 95.4%). The coefficient of determination (R2) values for the 50% and 80% passing sizes (X50 and X80) were 0.970 and 0.991, respectively, which demonstrated that the SAM could achieve high precision measurement of rock fragmentation. Additionally, the effectiveness of the SAM was further evaluated by comparing it to commercial software, and the generalizability of the SAM was verified on two other datasets. The findings revealed that the SAM not only outperformed the Split-Desktop V 4.0 on the test dataset but also achieved comparable accuracy to previous studies on the two other datasets. The SAM could be regarded as a useful tool to provide fast and accurate feedback for field blasting. [ABSTRACT FROM AUTHOR]

This document is an editorial for a special issue on "Valuable Metals Recovery by Mineral Processing and Hydrometallurgy." It emphasizes the importance of metals for society and the need for efficient techniques to process ores and extract metals. The recovery of metals from secondary sources, such as mining waste, is also highlighted. The editorial discusses various aspects and challenges of metal recovery, including the use of flotation in mineral beneficiation and the application of hydrometallurgical methods. It presents studies on grinding media, pulp oxidation-reduction potential, and the use of new reagents for metal recovery. The editorial also explores the extraction of metals from refractory ores and mining waste. Overall, the papers in this special issue demonstrate the potential for recovering valuable metals from various sources using modern techniques and theoretical frameworks. [Extracted from the article]

The uplift–depression framework controls the source–reservoir assemblage. However, the exploration breakthrough is restricted by an insufficient understanding of the uplift–depression differentiation framework in the Early Cambrian Keping–Wensu area. In this paper, based on field outcrops evaluations, thin section analysis, logging data, drilling data, and 3D seismic data, Wensu low paleo-uplift was discovered in the northern Tarim Basin, and the planar distribution was demonstrated in detail, generally shown as a SW–NE trending nose structure, extending roughly 114 km in length to the southwest, about 35 km in width to the northeast, and with the overall characteristic of being high in the west and low in the east. During the Early Cambrian, the Tabei paleo-uplift evolved into the Wensu low paleo-uplift and largely died out by the Middle Cambrian, with the development of ramps and rimmed carbonate platforms. The tectonic-sedimentary evolution of the uplift–depression framework controlled the development of a set of main source rocks and two sets of large-scale effective reservoir rocks in the Lower Cambrian, constituting two sets of effective hydrocarbon accumulation in the upper and lower stratigraphic parts of the basin. Among them, the upper assemblage holds more potential for hydrocarbon exploration, and is expected to be a next strategic target area for hydrocarbon exploration of Cambrian subsalt in the Keping–Wensu area. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study including LA-ICP-MS zircon U-Pb dating, geochemical, zircon Hf isotope, and whole rock Sr-Nd isotope analysis of magmatic rocks from the Yitong County, Jilin Province, NE China. These data are used to better constrain the Middle Silurian–Middle Devonian tectonic evolution in the eastern segment of the northern margin of the North China Craton (NCC). Zircon U-Pb dating results show that the Ximangzhang tonalite formed in the Late Silurian (425 ± 6 Ma); the basalt, andesite, and metamorphic olivine-bearing basalt in the Fangniugou volcanic rocks formed in the Middle Silurian (428 ± 6.6 Ma) and Middle Devonian (388.4 ± 3.9 Ma, and 384.1 ± 4.9 Ma). The Late Silurian tonalites are characterized by high SiO2 and Na2O and low K2O, MgO, FeOT, and TiO2, with an A/CNK ratio of 0.91–1.00, characteristic of calc-alkaline I-type granite. They are enriched in Rb, Ba, Th, U, and K, and depleted in Nb, Sr, P, and Ti, with positive εNd(t) (+0.35) and εHf(t) (+0.44 to +6.31) values, suggesting that they mainly originated from the partial melting of Meso–Neoproterozoic accretionary lower crustal material (basalt). The Middle Silurian basalts are characterized by low SiO2, P2O5, TiO2, and Na2O and high Al2O3, FeOT, and K2O, enriched in Rb, Ba, Th, U, and K and depleted in Nb, Ta, Sr, P, and Ti, indicative of shoshonitic basalt. The Late Silurian tonalites have positive εNd(t) (+4.91 to +6.18) values and primarily originated from depleted mantle magmas metasomatized by subduction fluids, supplemented by a small amount of subducted sediments and crustal materials. The Middle Devonian volcanic rocks exhibit low SiO2, TiO2, and Na2O and high K2O, and MgO, enriched in Rb, K, and LREEs and depleted in Nb, Ta, Sr, and HREEs, characteristic of shoshonitic volcanic rocks. Their εNd(t) (+2.11 to +3.77) and εHf(t) (+5.90 to +11.73) values are positive. These characteristics indicate that the Middle Devonian volcanic rocks primarily originated from depleted mantle magmas metasomatized by subduction fluids, with the addition of crustal materials or subducted sediments during their formation. Based on regional geological data, it is believed that the study area underwent the following evolutionary stages during the Silurian–Devonian period: (1) active continental margin stage of southward subduction of the Paleo–Asian Ocean (PAO) (443–419 Ma); (2) arc-continent collision stage (419–405 Ma); (3) post-collision extension stage (404–375 Ma); (4) active continental margin stage, with the PAO plate subducting southward once again (375–360 Ma). [ABSTRACT FROM AUTHOR]

The Shimensi super-large tungsten polymetallic deposit is located in the Late Jurassic–Early Cretaceous Porphyry–Skarn tungsten ore belt in the south Yangtze metallogenic belt. There are three types of mineralization: veinlet-disseminated type, thick quartz vein type and hydrothermal cryptoexplosive breccia type. Based on geological studies, this paper presents new petrographic, microthermometric, laser Raman spectroscopic and hydrogen and oxygen isotope research on the fluid inclusions from the deposit. The results show that there are five different types of fluid inclusions: liquid-rich inclusions, vapor-rich inclusions, pure liquid inclusions, pure vapor inclusions, and fluid inclusions containing a solid crystal. The homogenization temperatures of the fluid inclusion range from 140 °C to 270 °C, the salinities are 3 wt.%–5 wt.% NaCleq and the densities of ore-forming fluid range from 0.64 g/cm3 to 0.99 g/cm3. For the analyses of laser Raman spectroscopy, the ore-forming fluids can be approximated by a Ca2+-Na+-SO42−-Cl− fluid system with small amounts of CO2, CH4 and N2. Otherwise, the data of the pressure, pH and Eh show a fluid metallogenic environment of low pressure, weak acid and weak reduction. The values of the homogenization temperature in the three types of orebodies suggest that the mineralization is characterized by a decrease in temperature under the conditions of fluid immiscibility. The H-O isotope values are interpreted to indicate that the ore-forming fluids are mainly composed of magmatic water, and meteoric water is added with the process of magma rising. [ABSTRACT FROM AUTHOR]

Archaeometry can help archaeologists in many ways, and one of the most common archaeometric objectives is provenance analysis. Volcanic rocks are often found in archaeological sites as materials used to make grinding tools such as millstones and mortars or as building materials. Petrographic characterization is commonly applied to identify their main mineralogical components. However, the provenance study of volcanic stones is usually undertaken by comparing geochemical data from reference outcrops using common descriptive statistical tools such as biplots of chemical elements, and occasionally, unsupervised multivariate data analysis like principal component analysis (PCA) is also used. Recently, the use of supervised classification methods has shown a superior performance in assigning provenance to archaeological samples. However, these methods require the use of reference databases for all the possible provenance classes in order to train the classification models. The existence of comprehensive collections of published geochemical analyses of igneous rocks enables the use of the supervised approach for the provenance determination of volcanic stones. In this paper, the provenance of volcanic grinding tools from two archaeological sites (Iulia Libica, Spain, and Sidi Zahruni, Tunisia) is attempted using data from the GEOROC database through unsupervised and supervised approaches. The materials from Sidi Zahruni have been identified as basalts from Pantelleria (Italy), and the agreement between the different supervised classification models tested is particularly conclusive. In contrast, the provenance of the materials from Iulia Libica remained undetermined. The results illustrate the advantages and limitations of all the examined methods. [ABSTRACT FROM AUTHOR]

This paper follows up on a series of reference papers that inspired MDPI's Topic "Stochastic Geomechanics: From Experimentation to Forward Modeling", where global and local deformation effects on sand specimens are fully described from high-resolution boundary displacement fields, as supported by a comprehensive experimental database (which includes varying degrees of specimen's heterogeneity) that is available to the scientific community for further study. This paper presents an elasto-plastic comparative analysis of different finite element models reproducing different sand specimen heterogeneity configurations as follows: loose, dense, and half-dense half-loose specimens. The experimental conditions for these specimens' heterogeneity configurations were simulated with an axisymmetric finite element model. To characterize the stress-strain response obtained from the experiments, an elasto-plastic constitutive model with strain-hardening and softening laws was adopted to reproduce the sand specimens' mechanistic response. An expert-based calibration of the numerical models accounted for both global and local effects by making use of global observations captured by the triaxial point sensors (i.e., axial force and displacement) and by local observations captured by 3D digital image correlation analysis (i.e., 3D boundary displacement fields). Results show that predictions of the proposed numerical models are in good agreement with the experimental observations, both global and local responses. The combined use of global and local observations to calibrate sand triaxial specimens sets the basis for a more comprehensive parameterization process. For the first model set, three experiments were assumed with homogeneous materials. While both dense and loose models showed good agreement with the experiments, the displacement field prediction of the half-dense half-loose layered model identified limitations in reproducing heterogeneous configurations. Afterward, the second set compared and analyzed the half-dense half-loose layered models by implementing a heterogeneous model, showing significantly better model predictions (i.e., after the implementation of the heterogeneous model, which accounts for a transition zone between the upper and lower segments). [ABSTRACT FROM AUTHOR]

The safety and robustness of Deep Geological Repositories (DGRs) are of paramount importance for the long-term management of spent nuclear fuel from electricity generation. The introduction of a multi-barrier system, which includes the host rock formation and an engineered barrier system (including the bentonite buffer), has been a widely used approach to ensure the safety of DGRs. The assessment of the long-term safety of DGRs involves the mathematical modeling of the coupled thermal–hydraulic–mechanical–chemical (THMC) processes that occur in the near-field of the DGRs and their impact on the behaviour and engineering properties of the bentonite buffer. This paper presents a review of the THMC-coupled processes that arise in the bentonite buffer as well as a mathematical model governing such coupled processes. The model is verified against existing analytical solutions and validated against measured data of a thermal diffusion experiment in a sand bentonite column. Also, scoping analyses were performed to assess the influence of coupled THM processes on solute transport in clayrocks. The results of the numerical model closely matched those of the analytical solutions and experimental data demonstrating the capability of the provided mathematical model as well as the numerical approach in enhancing our comprehension of DGR behaviour. This enhanced comprehension will be valuable for safety prediction and assessment in the context of DGRs. The work presented in this paper is part of the Canadian Nuclear Safety Commission's (CNSC) regulatory research to gain independent knowledge on the safety of the geological disposal of radioactive waste. [ABSTRACT FROM AUTHOR]

The surface deformation caused by underground mining seriously affects the normal life and personal safety of local residents and also causes unfavorable factors for the safe and efficient exploitation of underground resources. While the study of surface deformation caused by underground mining of metal mines requires a large amount of measured data as support, the measured data is particularly scarce, which severely hinders the study of surface deformation caused by underground mining. In this paper, in order to study the impact of underground mining on surface structures in metal mines, we take the Fu Lao Zhuang Iron Mine in Anhui Province, China, as the research object and put forward a comprehensive measurement method based on the flat plate beam theory. Using empirical formulas combined with the methods of thickness-to-span ratio and the relaxation coefficient, etc., we carry out numerical simulation calculations for the displacement of the surface triggered by the mining of the ore body by using FLAC3D software. We calculate the maximum inclination deformation, curvature, and horizontal deformation values of the ground surface by referring to the displacement and deformation with reference to the displacement and deformation formula; the maximum tilt deformation, curvature, and horizontal deformation values of the ground surface are calculated, and finally, the permissible values of the design specifications are combined to make a judgment. The research results of this paper put forward the prerequisite for improving the surface deformation induced by underground mining. [ABSTRACT FROM AUTHOR]

Mine tailings are typically deposited as slurry and stored in impoundment dams. These structures pose a serious geotechnical risk, and are difficult to successfully reclaim at the end of mining. An increasingly common alternative to traditional tailings disposal is "dry stacking": the placement of tailings dewatered using filtration in a self-supporting stack. It has been demonstrated that the addition of rock (termed "commingling") to a filtered tailings stack has the potential to improve the geotechnical performance of the stack and may make large-scale dry stacking more economically viable. This paper discusses the application of commingling to tailings dry stacking, specifically relating to the design and evaluation of commingled blends of waste rock and tailings. The authors present a review of existing mix design theory, and present an extended theoretical model to predict the structure and behavior of blends of waste rock and tailings, based upon mix ratio and density. This paper is based upon established theory, but is extended to consider the case of loosely placed materials and the effect of volume change on structural configuration. The extended model may be used to describe the geotechnical behavior of commingled filtered tailings and waste rock. It is postulated that the geotechnical behavior of blends, and the primary mechanism of volume change, is governed by particle configuration. A brief discussion of experimental methods to evaluate the structure and configuration of commingled mine wastes is also presented. [ABSTRACT FROM AUTHOR]

Ion-adsorption-type rare-earth ores (IATREOs) that have experienced granite weathering have good permeability, and their leaching process involves the solute transport problem, which is dominated by convection. Because of the oscillation and dispersion errors of existing numerical methods for solving the convective-dominated solute transport equation, the results have low precision in the twin leaching process. In this paper, the convection–dispersion equation is decoupled into the dispersion equation, the convection equation, and the source-sink equation; the Crank–Nicolson and implicit difference methods are used to solve the dispersion equation and the source-sink equation, respectively. The solution of the convection equation is achieved on the basis of its physical interpretation. Therefore, a decoupling method for the convective-dominated solute transport equation is established. In comparison to the two examples with analytical solutions, the calculation errors of the method established in this paper are less than 2.00%, and it can solve the oscillation and dispersion problems. The rationality of the method is further demonstrated through the column leaching experiment of IATREOs. In comparison to the test results, the coefficients of determination of the breakthrough curves of rare-earth ions and ammonium ions calculated by the proposed method are all greater than 0.850, and the peak concentration error of rare-earth ions is less than 7.00%. This indicates that the proposed method can simulate the leaching process well. Furthermore, by combining the multiple/half method and the dichotomy method, an optimization method for determining the leaching agent amount was established to analyze the relationship between the leaching agent and the ratio of dispersion to pillar length. The results can provide a solution that can be used to mine IATREOs from experience to theory. [ABSTRACT FROM AUTHOR]

As an inherent property of the accumulation of elastic energy and the sudden instability failure of coal, coal bursting liability (CBL) is the basis of the research on the early warning and prevention of coal burst. To accurately classify the CBL level, the support-vector-machine (SVM) method was introduced in this paper, and the dynamic failure time (DT), elastic energy index (WET), impact energy index (KE) and uniaxial compressive strength (RC) were selected as the classification indexes. An imbalanced sample set, containing 95 groups of measured data of CBL, was established, and eight SVM classification models were constructed, based on different kernel functions and swarm-intelligence-optimization algorithms. Focusing on the problem of sample imbalance, the classification accuracy, A, F1-score and kappa coefficient were used to comprehensively evaluate the classification performance of SVM models, and the grey-wolf-optimizer SVM (GWO-SVM) model was selected as the best model in this paper, reaching the highest accuracy of 98.9%. The GWO-SVM was applied to identify the CBL level of the 4# coal seam in Xiaozhuang Coal Mine and the 1# coal seam in the Wanfeng Coal Mine. The results of the engineering application are consistent with those from the engineering field, and show that the proposed model is scientific and practical, and can be a new method for CBL classification. [ABSTRACT FROM AUTHOR]

Pyrite is an important proxy used to reflect the redox state of a sedimentary environment. Currently available studies on pyrite focus on the process of sulfur cycles between an ocean and sediment. However, our understanding of the biogeochemical cycle of sulfur in terrestrial lake basins remains unclear, and the growth patterns of different types of pyrite are poorly understood. In this paper, we used samples from the 34 section of the Qianjiang depression in the Jianghan Basin as direct research objects by combining pyrite and sulfur isotope determination. The one-dimensional diffusion–advection–reaction simulation (1D-DAR) model was applied to simulate the changes in the pyrite content and sulfur isotope values in the sediment. The results show that the sediments in the saline lake basin environment contain a high organic matter content, a high sedimentation rate, and a high H2S diffusion oxidation rate, reflecting the strong reducing background and high productivity of this ancient lake. Sensitivity tests revealed that the organic matter content and H2S diffusion oxidation rate at the sediment–water interface are sensitive to the pyrite content. The sedimentation rate, organic matter content, and sulfate concentration are sensitive to the pyrite's sulfur isotope values. However, the variation in the active iron content had little effect on the pyrite content or sulfur isotope value. [ABSTRACT FROM AUTHOR]

Hydrometallurgical gold recovery processes play a pivotal role in the gold mining industry, contributing to more than 90% of global gold production. Among the array of techniques available, the Merrill–Crowe process, adsorption, ion exchange, and solvent extraction are central in extracting gold from leach solutions. While the Merrill–Crowe process and gold complex adsorption onto activated carbon represent historical cornerstones, their inherent limitations have prompted the emergence of more recent innovations in ion exchange and solvent extraction, offering enhanced selectivity, control, and sustainability. The evolution of modern organic chemistry has significantly influenced the progress of ion exchange technology, mainly through the introduction of advanced polymer matrix synthetic resins. At the same time, novel solvents tailored to gold complex interactions have revitalized ion exchange and solvent extraction. Introducing ionic liquids and deep eutectic solvents has also added a new dimension to efforts to improve gold extraction metallurgy. This paper reviews these cutting-edge developments and their potential to revolutionize the hydrometallurgical gold recovery process, addressing the pressing need for improved efficiency and environmental responsibility. [ABSTRACT FROM AUTHOR]

The electron beam cold hearth melting (EBCHM) process is one of the key processes for titanium alloy production. The unique characteristic of this pyrometallurgy process is the application of the cold hearth, which is responsible for controlling the Low-Density Inclusions (LDIs) and High-Density Inclusions (HDIs) in the melt. As a key process of inclusion removal, the information such as melt residence time in the cold hearth is directly related to the control of metallurgical defects in the ingot, and may also affect the composition distribution of the ingot. In this paper, the details for the physical phenomena, namely the evolution of the pool, the evolution of the flow, and the evolution of the component in the cold hearth during EBCHM are investigated using a modified multi-physical numerical model. The effects of melting temperature and melting speed on these phenomena were investigated. The purpose is to provide more fundamental knowledge and to further enhance the applications of EBCHM for more titanium alloys. [ABSTRACT FROM AUTHOR]

The paper considers the possibility of changing the morphology of inclusions in diamonds based on the study of these inclusions and the inclusion–diamond boundary. Raman spectroscopy and transmission electron microscopy methods were used. According to the literature data, it is known that the octahedral form of mineral inclusions in diamond is induced, and does not correspond to the initial conditions of joint growth of diamond and inclusion, but the mechanism of this process is not considered. Solids differ in the value of surface Gibbs energy; the harder the material, the higher its melting point and the greater the value of surface Gibbs energy In the case of the diamond–inclusion pair, the surface energy of diamond far exceeds the surface energy of the inclusion. Diamond crystals have a surface energy value for an octahedron face of 5.3 J/m2, dodecahedron—6.5 J/m2, and cube—9.2 J/m2, i.e. it is anomalously high compared to the surface tension of silicate and other minerals. Therefore, the mineral inclusion in diamond tends to the form corresponding to the minimum of free energy in the "diamond–inclusion" pair, and when the energy of diamond dominates, the final shape will be determined by it, i.e. it will be an octahedron. The authors suggest the possibility of redistribution of diamond substance around the inclusion with simultaneous change of the inclusion morphology. [ABSTRACT FROM AUTHOR]

This paper reviews the phosphate phases in meteorites and those measured by landed spacecraft, what they reveal about past igneous and aqueous conditions on Mars, and important implications for potential prebiotic chemistry, past habitability, and potential biosignatures that could be detected in samples returned from Mars. A review of the 378 martian meteorites as of 2023 indicate that of the two most common phosphate minerals in Mars meteorites, merrillite and apatites, the apatite composition is largely F- and Cl-rich, with shergottites containing more OH. The phosphate concentrations examined across multiple missions show a relatively narrow range of phosphate, with higher concentrations observed in the Mount Sharp Group in Gale crater and Wishstone at Gusev crater and lower concentrations observed at Jezero crater floor and Jezero fan. Possible secondary phosphates detected on Mars, including Fe phosphates at Jezero crater and Gusev crater and Ca- and Al-bearing secondary phosphates, temperatures of formation of secondary phases and their dissolution rates and solubilities are reviewed and summarized. Despite this wealth of information about phosphates on Mars, due to their fine scale and relatively low concentrations, Mars Sample Return is needed to better understand phosphate and its implications for the igneous, aqueous, and astrobiological history of Mars. [ABSTRACT FROM AUTHOR]

Soil-improvement techniques with binders are used in several geotechnical engineering applications as a sustainable solution for the reuse of waste soils. Due to their inherent complexity and their mechanical behaviour, pyroclastic soils are generally considered waste geomaterials in their natural state. Lime treatment of pyroclastic soils can be considered a viable solution for their reuse in geotechnical applications. In this paper, some peculiar features of the chemo-physical evolution and mechanical behaviour of lime-treated pyroclastic soils are evidenced through a multi-scale experimental investigation. While, for clayey soils, the fine fraction is mainly responsible for ion exchange and pozzolanic reactions induced by lime, for pyroclastic soils, pozzolanic reactions are dominant processes due to the low quantity of clay minerals along with the abundance of aluminates and silicates as the main constituents of their amorphous phase. The link between the phenomena detected at the microscale level, the mineralogical composition, and the macroscopic behaviour of two lime treated pyroclastic soils of different origin is explored through a multiscale approach. [ABSTRACT FROM AUTHOR]