Search Results (91)

Acid mine drainage (AMD) remains a critical environmental challenge in South Africa due to its severe impact on water quality, ecosystems and public health. Numerous studies on AMD management, treatment and resource recovery have been conducted over the past 20 years. This study presents a comprehensive review of research activities on AMD in South Africa from 1998 to 2025, highlighting key trends, emerging challenges and future directions. The study reveals a significant focus on passive and active treatment methods, environmental remediation and the recovery of valuable resources, such as iron, rare earth elements (REEs) and gypsum. A bibliometric analysis was conducted to identify the most influential studies and thematic research areas over the years. Bibliometric tools (Biblioshiny and VOSviewer) were used to analyse the data that was extracted from the PubMed database. The findings indicate that research production has increased significantly over time, with substantial contributions from top academics and institutions. Advanced treatment technologies, the use of artificial intelligence and circular economy strategies for resource recovery are among the new research prospects identified in this study. Despite substantial progress, persistent challenges, such as scalability, economic viability and policy implementation, remain. Furthermore, few technologies have moved beyond pilot-scale implementation, underscoring the need for greater investment in field-scale research and technology transfer. This study recommends stronger industry–academic collaboration, the development of standardised treatment protocols and enhanced government policy support to facilitate sustainable AMD management. The study emphasises the necessity of data-driven approaches, sustainable technology and interdisciplinary cooperation to address AMD’s socioeconomic and environmental effects in the ensuing decades. Full article

The shear strength properties of ionic rare earth ore bodies are directly related to the stability of mine slopes, which provides important theoretical and engineering support for preventing geological disasters and ensuring the safe extraction of resources. This study investigates the effects of different confining pressures, leaching agent types, and MgSO₄ concentrations on the shear strength of ionic rare earth ores through triaxial shear tests. A scanning electron microscopy (SEM) analysis of post-shear mineral samples was conducted to examine the microscopic pore structure, revealing the evolution patterns of the ionic rare earth ore’s microscopic pore structure under various leaching conditions. The results show that the shear strength of the ore body varies significantly under different leaching conditions. After leaching, the shear strength values of the ore body, ranked from highest to lowest, are (NH₄)₂SO₄ > MgSO₄ > Al₂(SO₄)₃ > pure water. The (NH₄)₂SO₄ leaching group exhibited an average shear strength approximately 9.8% higher than the pure water group. When comparing the cohesion and internal friction angle of the pure water leaching group, the (NH₄)₂SO₄-leached ore body showed significantly higher cohesion and a smaller internal friction angle. In contrast, the MgSO₄ and Al₂(SO₄)₃ leaching groups demonstrated lower cohesion and higher internal friction angles. As the MgSO₄ concentration increases, the cohesion of the ore body gradually decreases, the internal friction angle increases, and the shear strength correspondingly increases. Under low-concentration MgSO₄ leaching, the number and area of pores in the ore samples initially increase and then decrease, leading to a more complex pore structure. At higher concentrations of MgSO₄, the variety of pore shapes increases and becomes more complex, pore randomness decreases, the probability entropy value decreases, and the pore distribution becomes more ordered. Full article

Rare earth elements (REEs) are critical mineral resources that play a pivotal role in modern technology and industry. Currently, the global supply of light rare earth elements (LREEs) remains adequate. However, the supply of heavy rare earth elements (HREEs) is associated with substantial risks due to their limited availability. Ion-adsorption type rare earth deposits (IAREDs), which represent the predominant source of HREEs, have become a focal point for exploration activities, with a notable increase in global interest in recent years. This study systematically collected stream sediments and stream water samples from the Jiaping IARED in Guangxi, as well as from adjacent granitic and carbonate background areas, to investigate the exploration significance of geochemical surveys for IAREDs. Additionally, mineralized soil layers, non-mineralized soil layers, and bedrock samples from the weathering crust of the Jiaping deposit were analyzed. The results indicate that stream sediments originating from the Jiaping IARED and granite-hosted background regions display substantially elevated REE concentrations relative to those from carbonate-hosted background areas. Moreover, δEu values in stream sediments can serve as an effective indicator for differentiating weathering products derived from granitic and carbonate lithologies. Within the mining area, three coarse-grained fractions of stream sediments (i.e., +20 mesh, 20–60 mesh, and 60–150 mesh) exhibit REE concentrations comparable to those observed in both granite-hosted and carbonate-hosted background regions. However, the HREEs content in the finer -150-mesh stream sediments from Jiaping IARED is markedly higher than that in the two background regions. The (La/Sm)_N versus (La/Yb)_N ratios of -150-mesh stream sediments in the Jiaping IARED may reflect the mixing processes involving HREE-enriched ore layer, non-mineralized layer, and LREE-enriched ore layer. This observation implies that fine-grained (-150-mesh) stream sediments can partially inherit the REE characteristics of mineralized layers within IAREDs. Scanning electron microscopy (SEM) observations indicate that the enrichment of REEs in fine-grained stream sediments primarily originates from REE-rich accessory minerals derived from parent rocks and mineralized weathering crusts. A comparative analysis reveals that the concentrations of REEs in stream water collected during the rainy season are significantly higher than those collected during the dry season. Moreover, the levels of REEs, especially HREE, in stream water from the Jiaping IARED substantially exceed those in background areas. Collectively, these findings suggest that the geochemical signatures of REEs in rainy season stream water possess diagnostic potential for identifying IAREDs. In conclusion, the integrated application of geochemical surveys of stream water and -150-mesh stream sediments can effectively delineate exploration targets for IAREDs. Full article

Multiple occurrences of adakitic rocks, with crystallization ages clustering around ~160 Ma, have been documented in the Zhuxi district, northeast Jiangxi Province, South China. This research identifies a new adakitic biotite granite porphyry within the Zhuxi W-Cu polymetallic deposit. Zircon U-Pb geochronology of this porphyry yields a crystallization age of 161.6 ± 2.1 Ma. Integrated with previously published data, the adakitic rocks in the study area—comprising diorite porphyrite, biotite quartz monzonite porphyry, and the newly identified biotite granite porphyry—are predominantly calc-alkaline and peraluminous. They exhibit enrichment in light rare-earth elements (LREEs) and depletion in heavy rare-earth elements (HREEs), with slight negative Eu anomalies. The trace element patterns are characterized by enrichment in Ba, U, K, Pb, and Sr, alongside negative Nb, Ta, P, and Ti anomalies, indicative of arc-like magmatic signatures. Comparative analysis of geological and geochemical characteristics suggests that these three rock types are not comagmatic. Petrogenesis of the Zhuxi adakitic suite is linked to a dynamic tectonic regime involving Mesozoic crustal thickening, subsequent delamination, and lithospheric extension. Asthenospheric upwelling likely triggered partial melting of the overlying metasomatized lithospheric mantle, generating primary mantle-derived magmas. Underplating and advection of heat by these magmas induced partial melting of the thickened lower crust, forming the biotite granite porphyry. Partial melting of delaminated lower crustal material, interacting with the asthenosphere or asthenosphere-derived melts, likely generated the diorite porphyrite. The biotite quartz monzonite porphyry is interpreted to have formed from mantle-derived magmas that underwent assimilation of, or mixing with, silicic crustal melts during ascent. The ~160 Ma crystallization ages of these adakitic rocks are broadly contemporaneous with W-Mo mineralization in the Taqian mining area of the Zhuxi district. Furthermore, their geochemical signatures imply a prospective metallogenic setting for Cu-Mo mineralization around this period in the Taqian area. Full article

Haigou deposit, located in Dunhua City, southeast Jilin Province, NE China, is a large-scale gold deposit. The gold ore body is categorized into two types: quartz-vein type and altered rock type, with the quartz-vein type being predominant. The vein gold ore body primarily occurs within the monzonite granite and monzonite rock mass in the Haigou area and is controlled by fault structures trending northeast, northwest, and near north-south. In order to constrain the age and tectonic setting of quartz vein-type gold mineralization, we conducted a detailed underground investigation and collected samples of monzonite granite and pyroxene diorite porphyrite veins related to quartz-vein-type gold mineralization for LA-ICP-MS zircon U-Pb dating and whole-rock main trace element data testing to confirm that monzonite granite is closely related to gold mineralization. Pyroxene diorite porphyry and gold mineralization were found in parallel veins. The zircon U-Pb weighted mean ages of monzonite and pyroxene diorite porphyrite veins are 317.1 ± 3.5 Ma and 308.8 ± 3.0 Ma, respectively, indicating that gold mineralization in monzonite, pyroxene diorite porphyrite veins, and quartz veins occurred in the Late Carboniferous. The monzonite granite and pyroxene diorite porphyrite veins associated with quartz vein-type gold mineralization have high SiO₂, high K, and high Al₂O₃ and are all metaluminous high-potassium calc-alkaline rock series. Both of them are relatively enriched in light rare earth elements (LREE) and macroionic lithophile elements (LILE: Rb, Ba, K, etc.), but deficient in heavy rare earth elements (HREE) and high field strength elements (HFSE: Nb, Ta, P, Ti, etc.), the monzonitic granite Eu is a weak positive anomaly (δEu = 1.15–1.46), the pyroxene diorite porphyre dyke Eu is a weak positive anomaly (δEu = 1.09–1.13), and the Nb and Ta are negative anomalies. The Th/Nb values are 0.28–0.73 and 1.48–2.05, and La/Nb are 2.61–4.74 and 4.59–5.43, respectively, suggesting that diagenetic mineralization is the product of subduction in an active continental margin environment. In recent years, scholarly research on Sr, Nd, and Pb isotopes in Haigou rock masses has indicated that the magmatic source region in the Haigou mining areas is complex. It is neither a singular crustal source nor a mantle source but rather a mixed crust-mantle source, primarily resulting from the partial melting of lower crustal materials, with additional contributions from mantle-derived materials. In summary, the metallogenic characteristics, chronology data, geochemical characteristics, and regional tectonic interpretation indicate that at least one phase of magmatic-hydrothermal gold mineralization was established in the Late Carboniferous as a result of the subduction of the Paleo-Asian ocean plate at the northern margin of the North China Craton. Full article

The South China region is characterized by diverse landforms and significant stratification of geological materials. The rock and soil layers in this area have obvious layering characteristics. The stability of layered slopes is a critical issue in the safe mining of southern ion-type rare earth ores. This study investigates the morphological changes, pore water pressure, and moisture content variation of layered ion-type rare earth ore slopes under the combined effects of rainfall and liquid infiltration through indoor model tests. A numerical simulation was conducted to analyze the variations in pore water pressure, moisture content, slope displacement, and safety factor under different working conditions. As rainfall intensity increases, the interface between soil layers in sandy–silty clay slopes is more likely to form a saturated water retention zone, causing rapid pore water pressure buildup and a significant reduction in shear strength. For the silty–sand clay slopes, the low permeability of the upper silty clay layer limits the infiltration rate of water, resulting in significant interlayer water retention effects, which induce softening and an increased instability risk. The higher the initial moisture content, the longer the infiltration time, which reduces the matrix suction of the soil and significantly weakens the shear strength of the slope. When the initial moisture content and rainfall intensity are the same, the safety factor of the silty–sand clay slope is higher than that of the sandy–silty clay slope. When rainfall intensity increases from 10 mm/h to 30 mm/h, the safety factor of the sandy–silty clay slope decreases from 1.30 to 1.15, indicating that the slope is approaching a critical instability state. Full article

Growing awareness of the environmental cost of mining operations has led to increased research on monitoring and restoring legacy mine sites. Hyperspectral imaging (HSI) has emerged as a valuable tool in the mining life cycle, including post-mining environment. By detecting variations in crystal structure and physicochemical attributes on the surface of materials, HSI provides insights into site environmental and ecological conditions. Here, we explore the capabilities of drone-based HSI for mapping surface patterns related to contamination dispersal in a legacy uranium-rare earth element mine site. Hyperspectral data across the visible to near-infrared (VNIR) and short-wave infrared (SWIR) wavelength ranges (400–2500 nm) were collected over selected areas of the former Mary Kathleen mine site in Queensland, Australia. Analyses were performed using data-driven (Spectral Angle Mapper—SAM) and knowledge-based (Band Ratios—BRs) spectral processing techniques. SAM identifies contamination patterns and differentiates mineral compositions within visually similar areas. However, its accuracy is limited when mapping specific minerals, as most endmembers represent mineral groups or mixtures. BR highlights reactive surfaces and clay mixtures, reinforcing key patterns identified by SAM. The results indicate that drone-based HSI can capture and distinguish complex surface trends, demonstrating the technology’s potential to enhance the assessment and monitoring of environmental conditions at a mine site. Full article

Carbonaceous shale has garnered significant interest as a viable alternative source of rare earth elements (REEs) besides conventional REE-bearing ores. This study characterized rare earth element + Yttrium+ Scandium (REYs) enrichment in the 11 core samples of carbonaceous shale (7) and coal (4) collected from Arnot Mine. Major elements of the studied carbonaceous shale (CS) and coal showed high amounts of SiO₂, Al₂O₃, and Fe₂O₃, indicating a high content of aluminosilicate and iron-rich minerals. The plots Na₂O + K₂O against SiO₂ suggested alkali granite, granite, and granodiorite provenance sources for the studied shale and coal. The samples showed enrichment in low and heavy rare elements crystallized from a low potassium tholeiitic and medium calc-alkaline magma based on the plots of La_N/Yb_N and K₂O vs. SiO₂. The mineralogical and maceral analysis revealed the dominant presence of kaolinite (15%–45%), and it was suggested as the cation exchange site resulting from the isomorphous substitution of Al³⁺ for Si⁴⁺. Additionally, siderite was suggested as one of the REY hosts due to the Fe³⁺ site forming a complex with the REE³⁺ ions. Furthermore, the samples were classified as lignite to sub-bituminous coal category with dominant minerals including kaolinite, quartz, and siderite. The outlook coefficient (Coutl) of REY in CS revealed a promising area for economically viable, having two enrichment types, including low (La, Ce, Pr, Nd, and Sm) and heavy (Ho, Er, Tm, Yb, and Lu). The Eu_N/Eu_N* and Ce_N/Ce_N* ratio for the current studied samples exhibited a weak negative to no anomaly, and most of the studied samples were characterized by distinctive positive Gd anomalies derived from sediment source regions weathered from alkali granite, granite, and granodiorite provenance formed from a low potassium tholeiitic and medium calc-alkaline magma. Full article

To understand the characteristics of the pollution risk of potentially toxic elements (PTEs) at a rare and precious metal mining site in Guangxi and to provide scientific evidence for the comprehensive evaluation and soil remediation of PTE pollution at the site, the Cd, As, Co, Cu, Cr, Ni, Pb, and Zn contents of five areas were determined. Laboratory testing was conducted on five soil plots in the selected five suspected contaminated areas (electroplating workshop, sewage treatment area, and boiler room). Correlation analysis, infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to evaluate and analyze PTE pollution. The average contents of Cd, Co, As, Pb, Zn, and Cu at the site were higher than the background values in the Guangxi soil. The Probability Mass Function (PMF) model was used to perform a source apportionment of the PTEs and determine the main pollution sources and their contribution rates. The results of the single factor pollution of the PTEs showed that Cd, Ar, and Cr were heavy pollutants, and Co was a light pollutant. The Nemerow comprehensive pollution index analysis showed that the study area was heavily polluted. The Earth accumulation index results show that Cd exhibited a very serious accumulation, Cu and Zn exhibited mild to moderate accumulations, and As and Co exhibited moderate accumulations. The FTIR results showed that C=O in the soil was chelated with PTEs in some samples, which weakened the characteristic peaks of C=O in proteins and polypeptides. The XRD results showed that cadmium hydroxide, lead oxide, and zinc hydroxide were present in the soil samples. The XPS results showed that the production of O²⁻ in the O 1s high-resolution spectra mainly came from the metal oxides produced by the polluting metals. Meanwhile, the microbial results showed that the pollution risk of PTEs affected the soil microbial community structure and diversity to some extent. Full article

In the present study, major oxide, trace, and rare-earth element (REE) contents in the stream sediments of the Ikuno and surrounding areas of the central part of Hyogo Prefecture in the Kinki district in southwestern Japan were analyzed. Several abandoned mines that contain Au, Ag, Cu, Pb, Zn, Fe, W, and As exist in these areas, including the Ikuno and Akenobe mines, which are famous historical mines. A total of 156 stream sediments over approximately 1300 km² in these areas were analyzed using X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). The spatial distribution patterns of elemental concentrations in the stream sediments in the Ikuno area were determined by three primary factors: the surface geology, the localized deposition of ore minerals, and the influence of the sedimentation of heavy minerals in the basin on local distribution. The mean value of the spatial distributions of the ore deposits was greater than the median, primarily due to the presence of concentrated regions near the mining sites. A Kolmogorov–Smirnov test indicated abnormal distribution patterns of Pb, Zn, Cu, Cr, and Ni due to the presence of exceptionally high concentrations of these elements at the mine sites. The stream sediments showed higher levels of light REEs, mainly La, Ce, and Nd, in comparison with the heavy REEs. This pattern, deviating from the global abundance, suggests the dominating influence of mining sites on local REE distributions. These findings are essential for assessing the environmental impacts of historical mining and developing strategies for responsible resource management in the region. By understanding the geochemical signatures of mining-affected areas, these data could contribute to future environmental monitoring and mitigation efforts, enhancing our understanding of environmental sustainability and responsible resource utilization. Full article

The Maoniuping Rare Earth Elements (REE) deposit, the second largest light REE deposit in the world, has been mined for decades, with serious impacts on the surrounding environment. However, the impact of mining on heavy metals in the downstream area (Nanhe River Basin) has not been systematically documented. To address this issue, this study explored the extent, transport, and accumulation of heavy metal contamination in the Nanhe River Basin through field surveys (2946 topsoil samples and four vertical soil sections) and regional geographic attributes (e.g., mining area, river, and elevation) combined with a variety of methods such as statistics, geostatistics, spatial analysis, geo-accumulation index, and potential ecological risk index. The results showed that soils in the Nanhe River Basin presented different degrees of heavy metal pollution, with Pb and Cd being the most abundant, and the soils as a whole showed moderate-heavy ecological risks. The spatial distribution and correlation of heavy metals exhibited similar distribution patterns and sources. Further analyses revealed that mining of REE in Maoniuping was the main source of heavy metal pollution in the Nanhe River Basin, with heavy metals entering the soil through runoffs. At the same time, mining activities led to the migration of heavy metals in different directions in the Nanhe watershed, i.e., about 1.3 km horizontally, 16 km longitudinally, and more than 1 m vertically. In addition, about 38.1 km² of the watershed is contaminated by mine wastes, which is 6.6 times the size of the mining area. In order to mitigate the threat of heavy metals, the local government has implemented water diversion projects and crop conversion in the Nanhe River Basin. This study provides a reference for research on the environmental problems caused by the exploitation of REE mines and other mineral resources. Full article

Ion adsorption rare earths are an important strategic resource, but their leach mining causes post-mining wastelands and tailings to suffer from soil sanding, acidification, and heavy metal contamination. This makes natural vegetation recovery difficult, relying mainly on artificial reclamation; however, the reclaimed vegetation grows poorly due to environmental stress. Hyperspectral remote sensing technology, with its high efficiency, non-destructive nature, and wide-range monitoring capability, can accurately estimate the physiological parameters of reclaimed vegetation. This provides support for environmental regulation in mining areas. In this study, three typical types of reclaimed vegetation in the Lingbei Rare Earth Mining Area, Dingnan County, Ganzhou City, were analyzed. Hyperspectral data and the corresponding chlorophyll content were collected to compare the spectral differences between reclaimed and normal vegetation. The spectral data were processed using mathematical transformation, fractional order differentiation, discrete wavelet transform, and continuous wavelet transform. Sensitive bands were extracted, and multispectral transformed feature bands were integrated. Linear and machine learning regression models were used to estimate chlorophyll content. The effects of different spectral processing methods on chlorophyll estimation were then analyzed. The results showed that reclaimed vegetation had higher spectral reflectance than normal vegetation, with the red valley shifting towards the long-wave direction and a steeper red edge slope. Different spectral transformation methods impact the accuracy of chlorophyll content estimation. Using appropriate methods can improve estimation accuracy. Fusing multi-spectral transformation features can achieve relatively good results. Among the models, the random forest regression model provides the best performance in estimating the chlorophyll content of reclaimed vegetation. This study provides a scientific basis for rapid and accurate monitoring of reclaimed vegetation growth in rare earth mining areas, supporting environmental management and decision-making and contributing to ecological restoration. Full article

A groundbreaking remote sensing approach that uses three Bastnäsite Indices (BI) to detect rare earth elements (REEs) was initially developed using ore samples from the Sulfide Queen mine in California and later applied to various well-studied ground-based, drone-based, airborne, and spaceborne imaging spectrometers across a wide range of scales, from micrometers to tens of meters. In this work, those same innovative techniques have revealed the existence of a potential site for extracting REEs. Data from AVIRIS-NG, AVIRIS-Classic, HISUI, DESIS, EnMAP, EO-1 Hyperion, PRISMA, and EMIT were utilized to map Ivanpah Dry Lake, which is located fourteen kilometers northeast of the Sulfide Queen mine. Although this area was not previously associated with REE deposits, BI maps have indicated the presence of a site that has remained enriched in REEs for decades, suggesting an opportunity for further exploration and mining. Historically, a pipeline transported wastewater from facilities at the Sulfide Queen mine to evaporation ponds on or near Ivanpah Dry Lake, where wastewater may have contained concentrated REEs. This research highlights imaging spectroscopy not only as a valuable tool for rapidly identifying and efficiently extracting REEs, but also as a means of recovering REEs from supposed waste. Full article

The ion adsorption rare earth (IARE) mining areas in southern China frequently experience severe seasonal drought, posing significant challenges to plant growth. This study investigates the hypothesis that rare earth elements (REEs) present in these mining areas induce drought resistance in Dicranopteris pedata (D. pedata). An experiment was designed with three drought stress intensities (0%, 5%, and 10% PEG6000) and three levels of rare earth element (REE) addition (none, low, and high). After 72 h of drought stress, physiological indices and metabolomic profiles of D. pedata were examined. The results showed that under drought conditions, the REE additions increased the catalase and peroxidase activities of D. pedata by 99.04% and 81.25%, respectively, and the contents of proline, soluble proteins, and soluble sugars by 97.52%, 71.24%, and 61.81%, respectively. Metabolomic analysis revealed up-regulation of lipid and lipid-like molecules, as well as flavonoid metabolism, which contribute to improved drought resistance in D. pedata under stress. Furthermore, REE addition further up-regulated flavonoid and anthocyanin synthesis compared to drought stress alone, enhancing the plant’s resilience to drought. These findings suggest that D. pedata responds to drought stress by modulating enzyme activities, osmoregulatory substances, and metabolic pathways upon REE exposure. This study underscores the dual role of REEs in enhancing both the drought tolerance and enrichment capacity of D. pedata in IARE mining areas, which is crucial for sustaining plant growth amidst drought stress, and provides new ideas for the ecological restoration and sustainable development of IARE mining areas. Full article

Intermediate-acidic granites occur extensively in the Chazangcuo copper-lead-zinc mining area (hereinafter referred to as the Chazangcuo mining area) in Tibet, China. Exploring their rock types, sources, and tectonic settings is essential for understanding the genesis of granites in the region. This study investigated the petrology of the Chazangcuo granites, as well as the geochemical characteristics of their major elements, trace elements, and rare earth elements (REEs). Results indicate that the Chazangcuo granites are high-K calc-alkaline metaluminous rocks. These granites are enriched in large-ion lithophile elements (LILEs; e.g., Rb and Ba), depleted in high-field-strength elements (HFSEs; e.g., Nb, Ta, Zr, and Hf), with a relative enrichment in light rare earth elements (LREEs), and relatively depleted in heavy rare earth elements (HREEs), exhibiting a V-shaped distribution pattern and weak negative Eu anomalies. The granites are classified as typical I-type granites, displaying characteristics of crust-derived magmas with contributions from mantle sources and exhibiting significant fractional crystallization. The Chazangcuo granites were derived from the partial melting of mafic rocks, with protoliths formed in a moderate temperature environment. Influenced by the subduction of the Neotethys Ocean, the Chazangcuo granites were formed in an arc caused by the collision between the Indian and Eurasian plates (also referred to as the Indo–Eurasian collision) during the Late Triassic. Under the effect of geological activities such as upwelling of the asthenosphere and fluid intrusion and differentiation, metal mineralization was prompted to be distributed in the granite fissures, forming the Cu-Pb-Zn polymetallic deposits of Chazangcou in Tibet, suggesting that the granites are closely associated with mineralization. Full article