The Jinchang deposit is a large Au deposit in the Yanbian–Dongning region, in Northeast China, and is the product of magmatic–hydrothermal activities related to Early Cretaceous concealed igneous intrusions. However, these Early Cretaceous ore-causative igneous intrusions and the ore-hosting rocks in the Jinchang ore district have rarely been studied, with their magma sources and tectonic settings being ambiguous. Here, we integrate new geochemical, zircon U–Pb and Hf isotopic data from the concealed ore-hosting monzogranite and the ore-causative granodiorite to constrain their magma sources and tectonic settings. Zircon U–Pb dating indicates that the two monzogranites from the drill holes J_IZKN01 and J₁₈ZK0303 have similar crystallization ages of 202.0 ± 1.6 and 200.9 ± 1.2 Ma, respectively, whereas the granodiorite from the drill hole J_XI-1ZK1001 was formed in the Early Cretaceous period (107.0 ± 3.0 Ma). They are all enriched in large-ion lithophile elements (e.g., Rb, Th, and K) and light rare-earth elements, depleted in high field strength elements (e.g., Nb, Ta, and Ti) and heavy rare-earth elements, and yield similar positive εHf(t) values of +4.4 to +11.5, with their two-stage model ages ranging from 799 to 389 Ma. These results indicate that the concealed Early Jurassic ore-hosting monzogranite was derived from the partial melting of the Neoproterozoic–Paleozoic continental crust in a continental arc setting related to the Paleo-Pacific subduction. The ore-causative granodiorite originated from the partial melting of both the mantle wedge and the overlying continental crust, most likely caused by the dehydration and metasomatism of the subducted Paleo-Pacific slab involved in the rollback in the Early Cretaceous period. Full article

The Zhashui-Shanyang ore cluster area is one of the most important gold polymetallic ones in northwestern China. The Qinglingou gold deposit is a newly discovered small-scale deposit in the Zhashui-Shanyang area. Gold mineralization closely related to acid intrusive rocks has been found for the first time in this area. In this paper, the geochronology, whole-rock geochemistry, and isotope signature of the granite porphyries in the deposit are studied. They are characterized by variable medium SiO₂ (67.22–71.72 wt.%), high K₂O + Na₂O contents (6.54–10.34 wt.%), and variable Al₂O₃ (14.47–15.10 wt.%) values. The A/CNK ratios range from 0.90 to 1.23, and the A/NK ratios vary from 1.14 to 1.48. These rocks also contain biotite and amphiboles and are similar to peraluminous and high-K calc-alkaline I-type granites. The Qinglingou granite porphyries show relative enrichment of Rb, Th, and K, and depletion of Nb, Ta, P, Ti, and other high field strength elements. These porphyries are enriched in light rare earth elements relative to heavy rare earth elements with weak negative Eu anomalies (δEu = 0.63–0.89), which is interpreted to be the best age of crystallization of the Qinglingou porphyries. LA–ICPMS zircon U–Pb dating yields an age of 211 ± 1.2 Ma (n = 16, MSWD = 0.39). The close spatial relationship between the ore bodies and granite porphyry dikes indicates that this age may represent the metallogenic age in this area. The zircons have ¹⁷⁶Hf/¹⁷⁷Hf ratios ranging from 0.282625 to 0.282702, the ε_Hf(t) values are near 0 and the two-stage zircon Hf model ages range from 1121 to 1296 Ma. These data indicate that the Qinglingou granite porphyries were derived from the interplay between mantle- and crustal-derived magmas. We therefore propose that there is potential gold in carbonate rocks at the periphery of porphyry-skarn copper-molybdenum deposits. Full article

The Weishan REE deposit is located in the southwest of the Luxi Terrane of the North China Craton (NCC), where a large number of lamprophyre dikes are spatially exposed with the deposit. Here, we report petrology, geochemistry and zircon U-Pb geochronology data for the lamprophyre of the Weishan REE deposit in order to develop constraints for the determination of the petrogenesis, magma source and evolution of the lamprophyre and the tectonic environment. LA-LCP-MS zircon U-Pb dating shows that the crystallization age of the lamprophyre is 125 ± 0.86 Ma. The geochemical data suggest that these lamprophyres have high levels of Al₂O₃, K₂O, MgO and alkalis, moderate level of Na₂O and low levels of SiO₂, Fe₂O₃ and TiO₂, and that they are enriched with LREEs (La, Ce) and LILEs (Rb, Ba) and depleted with regard to HREEs and HFSEs (Nb, Ta, Ti). They displayed negative εHf(t) values of −14.98 to −9.03, T_DM1 ages of 1.1–1.4 Ga and T_DM2 ages of 1.7–2.1 Ga, which suggest that the magma source originates from an enriched mantle. Low Rb/Sr and high Dy/Yb ratios suggest that the enriched mantle source was partially melted at the amphibole-bearing lherzolite garnet-facies. The high Ba/Th and Sr/Th ratios indicate that the enriched source was derived from subduction dehydration fluids of the oceanic crust. We propose that the mafic dike intrusions are consistent with an Early Cretaceous alkaline magma emplacement in an extensional setting, in which the magma was not contaminated by crustal material during its emplacement. Full article

Unhydrated aminopropyl triethoxysilane was used to modify calcined kaolin produced from coal-bearing kaolinite. The aim was to develop a simple and economic modification method without the need for solution immersion and subsequent wastewater treatment. The samples before and after modification were tested using multiple methods, such as XRD, MAS-NMR, FT-IR, XPS, and SEM. The study results indicate that this modification can effectively improve the surface property of calcined kaolin. The activity index increased to 76.7% when the modifier usage was 2%. With a further increase in the modifier content, the activity index decreased. Surface modification did not reduce the whiteness of calcined kaolin. Further, the modification reaction mechanism was elucidated. Based on the detailed analyses, it was found that the modification reaction took place between the NH₂ groups in the modifier molecules and Al^VI-OH in calcined kaolin, and hydrogen bonds were formed between the NH₂ groups and the active sites on the calcined kaolin surface. Full article

The construction of an underground coal mine reservoir plays an essential role in the ecological environment of arid areas. The moisture content and loading angle inclination significantly impact the strength and stability of the safety coal pillar of underground reservoirs. Water-bearing coal was investigated under a coupled compression–shear load using inclined uniaxial compression tests on coal samples with varying water contents (ω = 0%, 2.42%, 5.53%, 7.55%, and 10.08%) and acoustic emission (AE) technology. The weakening mechanism of the mechanical property parameters and the crack evolution law, combined with the characteristics of the stress–strain curve, the cumulative AE count, and the cumulative AE energy methods, were used. Therefore, the evolution law of the coal’s crack closure (CC) threshold, crack initiation (CI) threshold, and crack damage (CD) threshold was analyzed. The results indicate that coal samples’ peak stress and elastic modulus decreased when the water content or inclination angle increased. Peak shear stress decreased as the water content rose, and the overall characteristics gradually rose as the inclination angle increased. The exception was when the ratio was 10.08%; when the inclination angle was 0°, the failure mode of the coal sample progressively changed from tension failure (ω = 0%, 2.42%) to tension–shear composite failure (ω = 5.53%), and finally to shear failure (ω = 7.55%, 10.08%). When the inclination angle was 5°, the coal sample was dominated by tension–shear composite failure at any moisture content. When the inclination angle was 10° and 15°, the coal specimens showed shear failure at any moisture content. The evolution law of tensile and shear cracks determined by AE characteristic parameters was consistent with the macrofracture characteristics of the coal specimens. When the water content or inclination angle increased, the crack closure threshold, crack initiation threshold, and damage threshold of the coal samples decreased. Therefore, these results show that their peak stress ratio does not depend on the water content or inclination angle. Full article

The characterization and leaching mechanism of REEs from phosphogypsum (PG) in HCl was studied in-depth. REEs contained in the PG were 208 ppm, of which Y, La, Ce, and Nd were the four most abundant elements. The modes of occurrence of rare earth elements (REEs) in the PG were quantified using the sequential chemical extraction (SCE) method. Among the five REE occurrence species, the metal oxide form accounted for the largest proportion, followed by the residual, organic matter, and ion-exchangeable fractions, and REEs bound to carbonates were the least. From the comparison of the distributions of REEs and calcium in different occurrence states, it can be determined that REEs contained in the PG were mainly present in the residue state (existed in the gypsum lattice) and the metal oxide state (easily leached). The leaching results show that the suitable leaching conditions were acid concentration of 1.65 mol/L, S/L ratio of 1/10, and reaction temperature of 60 °C. At the condition, the maximum leaching efficiency for ∑REE was 65.6%, of which the yttrium leaching rate was the highest and reached 73.8%. Importantly, A new kinetic equation based on the cylindrical shrinking core model (SCM) was deduced and could well describe REE leaching process from PG. The apparent activation energy for ∑REE leaching was determined to be 20.65 kJ·mol⁻¹. Full article

A field trial was conducted in Inner Mongolia to evaluate the stabilization effects of phyto-stabilization, biochar-stabilization, and their coupled stabilization for As, Cu, Pb, and Zn in soil. Stabilization plants (Achnatherum splendens, Puccinellia chinampoensis, and Chinese small iris) and biochar (wood charcoals and chelator-modified biochar) were introduced in the field trial. The acid-extractable fraction and residual fraction of the elements were extracted following a three-stage modified procedure to assess the stabilization effect. The results after 60 days showed that the coupled stabilization produced a better stabilization effect than biochar-/phyto- stabilization alone. Achnatherum splendens and Puccinellia chinampoensis were found to activate the target elements: the residual fraction proportion of As, Cu, Pb, and Zn decreased while the acid-extractable fraction proportion of Cu and Zn increased in the corresponding planting area. Neither type of biochar produced a notable stabilization effect. The residual fraction proportion of As (20.8–84.0%, 29.2–82%), Pb (31.6–39.3%, 32.1–48.9%), and Zn (30.0–36.2%, 30.1–41.4%) increased, while the acid-extractable fraction proportion remained nearly unchanged after treatment using Chinese small iris-straw biochar or Achnatherum splendens-straw biochar, respectively. The results indicate that phyto-stabilization or biochar-stabilization alone are not suitable, whereas the coupled stabilization approach is a more efficient choice. Full article

Granulated blast furnace slag (GGBFS) is a potential resource of rare earth elements (REEs), and due to the complex mineralogy, extraction by conventional hydrometallurgical process makes it an acid-consuming method. Bioleaching is thus investigated using a chemo-organotrophic bacterium Gluconobacter oxydans (DSMZ 46616) for REE extraction from GGBFS containing 157 ppm Ce, 90 ppm La, 71 ppm Nd and 40 ppm Er, hosted in a Ca-Al-Si matrix. The gluconic acid generation by G. oxydans was assessed for its role in REE extraction from GGBFS. With 5% (w/v) GGBFS using a mixture of a non-adapted and a GGBFS-adapted culture, a maximum solubilization of 67% and 88% Nd was observed after 12 and 40 days of incubation, respectively. The total amount of gluconic acid excreted by the bacteria increased with leaching duration, which contributed to a rise in metal extraction. Scanning electron microscope-energy dispersive analysis (SEM-EDAX) analysis of the solid residue showed bacterial cells in corrosion pits, and thereby assisting in metal solubilization. Full article

This study details the investigation of a black powder potential ore that was first obtained from Jiangxi, China. Its species, composition, and morphology are unknown. Preliminary tests revealed that the silica (SiO₂) content of this ore is >70%. To test this ore more comprehensively, its mineralogical parameters (such as mineral composition, ore particle size, and mineral morphology) are investigated using X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), differential scanning calorimetry–thermogravimetry (DSC-TG), Fourier-transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), laser particle size analysis, and elemental analysis (EA). Based on these analyses, it is determined that it is micro/nano silicon-carbon ore, and its genesis and species are discussed herein. The gangue minerals, such as α-quartz, kaolinite, pyrite, and muscovite, are finely disseminated and encapsulated by fixed carbon. The ore has an uneven morphology, with many holes and depressions. Moreover, nano-sized needle-like quartz and quartz wrapped by carbon are found on the surface of the ore. According to our results, this ore may have been formed by the long-term accumulation and consolidation of phytoliths. These results provide a technical reference for the development and utilization of the identified micro/nano silicon-carbon ore. Full article

The application of finite element analysis is used to simulate the relative distribution and magnitude of stress–strain conditions during a geologically brief, NNW-SSE-oriented, extensional event (1595 Ma to 1590 Ma), co-incident with IOCG-hydrothermal fluid flow and mineralisation across the Mt Woods Inlier, Gawler Craton, South Australia. Differential stress and shear strain maps across the modelled terrane highlight regions that were predisposed to strain localization, extensional failure and fluid throughput during the simulated mineralisation event. These maps are integrated with other datasets and interpretation layers, one of which is a proposed structural–geometrical relationship apparent in many world-class IOCG deposits, including Prominent Hill, Olympic Dam, Sossego, Salobo, Cristalino and Candelaria. These deposits occur at steeply plunging, pipe-like intersections of conjugate extensional systems of faults, shears and/or contacts, wherein the obtuse angle may have been bisected by the maximum principal extensional axis (viz., σ₃) during mineralisation. Several other layers are also used for the generation of targets, such as distance from major shear zones, favourable host lithologies, and proximity to tectonostratigraphic contacts of markedly contrasting competency. The result is an integrated target index or heat map for IOCG prospectively across the Mt. Woods Inlier. Full article

The experimental study on the water-holding characteristics of remolded loess was carried out, revealing the variation of water-holding characteristics with particle size composition and dry density. The results show that the air-entry value is positively correlated with the silt-sized content and negatively correlated with the sand-sized content. During the dehumidification of the specimens at a fixed dry density, when the air-entry value is between 9 and 10 Kpa, it is strongly influenced by the silt-sized content; however, beyond 10 Kpa, the sand-sized content is an important influencing factor. Changes in particle size composition have less influence on the residual water content. There is a non-linear relationship between the particle size composition and the slope λ of the dehumidification curve in the transition zone. Air-entry values, residual water content, saturated volumetric water content, and λ correlate well with dry density. Simulation tests were carried out using two power function models, including three variables. It was found that the VG model is a better fit than the Gardner model. Full article

With the exploring and developing of mineral resources in the Tibet Autonomous Region for many years, a large number of tailings have been produced. A total of 17 tailings samples from borehole cores were collected from different tailings ponds in different regions of Tibet. The results showed that the mineral composition and content of tailings in each research area were different. Among them, quartz was the most abundant mineral in most tailings. The major elements of tailings mainly included Si, Al, Fe, Mg, Mn, Ca, Na, K and so on. S existed in different types of tailings. In the analysis of trace element composition, it was found that the content of some elements had approached the lowest industrial grade, which has potential recycling value, such as Mn, Zn, Pb and P. Through the detection of radioactive elements (Ra-226, Th-232 and K-40), it was shown that there were great differences among different types of tailings, and their different contents would bring potential hazards to the safety of the surrounding environment and human health. Similar results were found in the analysis of particle size characteristics of tailings. These results are of great significance for the future utilization and resource utilization of tailings pond. Full article

The rapid development and intensive production of aquaculture have brought to light various environmental problems. In particular, fish farming adversely affects the benthic environments through the accumulation of organic matter (OM), which leads to the degradation of aquatic sediments and associated biotic communities. To prevent environmental degradation, proper site selection for fish farming is a prerequisite for sustainable aquaculture practices. An important physical factor in selecting a site for fish farming is sediment structure. Coarser sediments are preferred, while their mineral composition is rarely discussed. To investigate relationships between sediment characteristics and the content of OM, sediments were collected from three different sites with different aquaculture practices under different climatic and environmental conditions and analyzed during the one-year monitoring period. Grain size distribution, mineral composition, carbonate content, and organic matter content were determined for three fish farm sites (Ilova, River, Krka River, and Pelješac) and their reference sites. Preliminary results from all studied sites showed that sediment texture in combination with natural mineral composition is one of the key factors for the accumulation of OM in the sediment. In particular, the mineral composition of the fine-grained sediment should be known when conducting an environmental impact assessment of fish farms. Full article

The correct management of industrial waste, as well as being an environmental obligation, can also be used as an opportunity to reduce costs in terms of energy and raw material consumption. A large amount of waste sand is generated in foundries with a high content of pollutants adhering to its surface structure. In this study, the material utilized consists of a silicic sand that comes from a casting process, with a thin layer of fixed carbon on the surface of the particles. The objective is to remove this contaminant, in order to have clean sands for use in alternative processes, such as in glass raw material, green concrete, or in the recirculation of these in the same process. The mechanical action that is best for eliminating surface attached contaminants is abrasion. In this regard, two specific devices, commonly used in ore processing operations, were utilized to apply energy in a material in order to reach abrasion by attrition, but with different kinetic approaches: stirring in a slurry media and using a light milling, in both cases reducing the grinding media in order to avoid material fracture. The test performance evaluation is mainly focused on the decontamination efficiency, the sand mass recovery ratio, and the energy consumption. The results show that in all cases, liberation is reachable in different levels at different residence times. We were able to decrease the LOI content from 4% to less than 1%, combined with a near 85% recovery rate of clean sand in the case of stirring. In the case of light milling, the results are even better: the final product reached near 0.5% of LOI content, despite mass flow recovery potentially being less than 80%. Finally, we discuss whether energy consumption is the factor which decides the best alternative. The energy consumed ratio when comparing light milling with stirring is near 9:1, which is a significant amount when taking into account the importance of reducing energy consumption in today’s industry due to its economic and environmental impact. Full article

Generalization of the results of the study of placer gold and the mechanisms of its distribution in the east of the Siberian Platform made it possible for the first time to reveal that the ore sources of gold-bearing placers were mainly mineralization of the gold-sulfide formation formed under the influence of hydrothermal metasomatic processes occurred in deep fault zones. It is determined that the gold-bearing hydrothermal-metasomatic formations of the gold-sulfide rock formation are amagmatic, near-surface, low-temperature and spatially confined to deep faults. These formations are widespread in terrigenous-carbonate strata and sand deposits of PZ-MZ age and are observed in the zones of brecciation, silicification, and ferruginization. The analysis of the mechanisms of distribution of hydrothermal-metasomatic gold-bearing formations in the east of the Siberian Platform, based on previously conducted research of predecessors and our field observations, allowed us to establish the following. In the northeast, hydrothermal-metasomatic formations occur in the field of development of the Zhigansky fault, the Molodo-Popigai and Anabar-Eekite fault system, in the central part of the east of the Siberian Platform, the Vilyui paleorift (Kempendyai dislocations), and in the southeast in the Baikal-Patom thrust belt in ancient faults (Bappagai, Khorinsky, etc.). Metasomatites of hydrothermal origin form extended narrow formations along ancient faults activated in the Mesozoic, as well as conformable deposits in the Vendian, Cambrian carbonate strata, Jurassic and Cretaceous sandstones. It is proved that these formations are amagmatic and are not related to the widespread magmatism of the basic composition, which is confirmed by the homogenous mineral composition of metasomatites, independent of the composition of magmatic bodies spatially located with them. Zones of metasomatites with gold mineralization contain Au from 0.5 to 3.0 g/t, and in isolated cases up to 24–32 g/t. Gold is represented from finely-dispersed to visible fine, with a size from 0.01 to 0.5 mm or more. It is known that hydrothermal-metasomatic processes on the territory of Central Aldan contributed to the formation of large deposits such as Kuranakh, Tabornoye and others. It is possible that the identified gold-ore metasomatites, developed along the zones of regional faults and not confined to magmatic formations, widely occurred both in the northeast and in the southeast of the Siberian Platform, represent a huge metallogenic potential. Full article