Search Results (1,025)

Heilongjiang Province, northeastern China, occupies a key metallogenic position between the eastern Central Asian Orogenic Belt and the western Pacific continental margin. This review integrates published geological, geochronological, fluid–inclusion, and H–O–S–Pb isotope data to evaluate tectonic controls on endogenic gold mineralization. Four principal metallogenic episodes are recognized: Caledonian porphyry-related mineralization associated with Paleo–Asian Ocean subduction–accretion; Variscan skarn-forming magmatic–hydrothermal activity; Indosinian post-collisional structurally focused and epithermal hydrothermal activity; and Yanshanian mineralization characterized by Late Jurassic compressional reworking followed by a dominant Cretaceous Paleo–Pacific-related magmatic–hydrothermal pulse. Ore-forming fluids evolved non-monotonically from Paleozoic high-temperature magmatic fluids to more heterogeneous crustal, metamorphic, and meteoric–water–influenced systems. Zhengguang and Laozuoshan provide clear evidence for temporally distinct superimposed mineralization. Later hydrothermal reactivation could either remobilize and reconcentrate Au or leach, disperse, and obscure earlier mineralization. Exploration should therefore prioritize reactivated structural corridors where intrusive centers, reactive wall rocks, volcanic basins, and multi-stage alteration overlap. Full article

Deep exploration in mature gold districts requires subsurface alteration evidence that can be related quantitatively to three-dimensional (3D) geological architecture. This study develops a workflow for the Tudui–Shawang deposit in the Muping–Rushan metallogenic belt that integrates drill-core short-wave infrared (SWIR) spectroscopy, 3D alteration modeling, ore-controlling geological constraints, positive–unlabeled (PU) learning, and ensemble prospectivity prediction. A total of 2140 spectra from 10 drillholes were processed to identify mineral assemblages, extract spectral scalars and feature-shape attributes, classify alteration facies, and construct continuous 3D alteration evidence. Discrete smooth interpolation and indicator kriging were used for continuous and categorical attributes, respectively, and CatBoost, LightGBM, XGBoost, and Random Forest were evaluated within a spatially separated PU-bagging design. Quantitative analyses show that individual SWIR attributes have weak deposit-scale relationships with Au grade. Nevertheless, local IC minima, relatively lower pos2200 values near several mineralized intervals, alteration-facies transitions, and a broader shift toward longer pos2250 wavelengths characterize relevant parts of the mineralized system. FUSE performed best under 1 km × 1 km spatial holdout validation, with an ROC AUC of 0.8900 and a PRAUC of 0.8926. Prediction-area analysis and the 3D probability volume delineated three ranked exploration targets (T1–T3). The results show that drill-core SWIR-derived 3D alteration evidence, when integrated with ore-controlling geology and spatially validated machine learning, provides a practical basis for target prioritization in mature gold districts. Full article

Selective recovery of gold from cyanide leach liquors is hindered by the co-dissolution of iron minerals that generate ferrocyanide complexes which strongly compete with [Au(CN)₂]⁻ at ion-exchange sorbents. Here, we investigate mixed-bed interpolymer systems (IPS) composed of a strong-acid sulfonated polystyrene–divinylbenzene cation exchanger (TC007, Na⁺ form) and a strong-base quaternary ammonium anion exchanger (AV-17-8, Cl⁻ form) as a charge-selective platform for gold cyanide recovery. IPS compositions spanning cation-to-anion molar ratios from 6:0 to 0:6 were evaluated in batch contact with binary model solutions containing 30 mg L⁻¹ each of [Au(CN)₂]⁻ and [Fe(CN)₆]⁴⁻ at pH 10 and 25 °C. The optimal 1:5 IPS achieved an [Au(CN)₂]⁻ extraction degree of 79.88% and a selectivity coefficient β = D_Au/D_Fe = 4.95 at 48 h, whereas the pure AV-17-8 anion exchanger (0:6) reached only 37.55% Au extraction at 48 h, following an atypical delayed-uptake kinetic profile rather than the rapid, near-quantitative capture expected of an unmodified strong-base resin. Sorption kinetics were best described by a pseudo-second-order model (R² = 0.9992), confirming ion exchange at quaternary ammonium sites as the dominant rate-controlling step, with a ~30-fold increase in k₂ for [Au(CN)₂]⁻ in the 1:5 IPS relative to AV-17-8 alone. FTIR spectroscopy and TGA-DSC revealed the incorporation of metal cyanide complexes into the IPS matrix, with diagnostic C≡N stretching bands at 2108.7 and 2034.1 cm⁻¹ and an additional thermal event at 200–280 °C. These findings establish compositionally tunable IPS based on commercially available resins as a charge-selective sorbent platform demonstrating a capacity to regenerate under single-cycle elution conditions for gold cyanide recovery from ferrocyanide-containing process streams while highlighting the need for further evaluation under industrial Fe:Au ratios. Full article

Gold in the coarse-grained alluvial sediments of the Irgaity placer deposit (Kazakhstan) occurs predominantly as finely dispersed particles associated with mineral matrices, which limits the efficiency of conventional recovery methods. The proposed processing flowsheet demonstrated that thermal pre-treatment is an effective approach for enhancing ultrafine gold recovery, achieving an overall recovery of 86% from the treated concentrate. The Tescan TIMA “Bright Phase Search” workflow, optimized for gold detection by applying a minimum BSE brightness threshold of 75% and an Au phase filter calibrated using a gold standard, successfully identified gold-bearing grains within the analyzed mounts. Further mineralogical investigations revealed that gold particles ≤10 μm occur as native gold and Au-Ag-As-bearing phases, with silver content reaching up to 14 wt.% in some coarser grains. The significant association of silver with gold-bearing particles indicates the potential for incorporating silver recovery into the processing flowsheet, thereby improving the overall economic value of the deposit. Despite the low average gold grade (0.3–0.4 g/t), the large dimensions of the Irgaity placer deposit (approximately 12 km long, 1.5 km wide, and 60–70 m thick) suggest the presence of a substantial large-volume mineral resource. The combination of extensive mineralized sediments and high recovery achieved through thermal activation supports the potential economic viability of the deposit and warrants further evaluation of its development potential. Full article

Pneumoconiosis remains a major problem globally with a much higher burden in low- and middle-income countries (LMICs). There is increased inter-reader variability in the classification of pneumoconiosis in most LMICs. Despite the use of the International Labour Organization (ILO) International Classification System that standardizes reporting of pneumoconiosis on chest radiographs, inter-reader variability persists. We aimed to assess inter-reader concordance in classifying pneumoconiosis using the ILO International Classification System among artisanal and small-scale gold miners (ASGMs) in Zimbabwe. A retrospective cross-sectional study was conducted using 576 eligible chest radiographs (dicom format). Overall agreement for binary classification was moderate (κ = 0.522, 95% CI: 0.475–0.569), with pairwise agreement ranging from moderate to substantial (κ = 0.464, 95% CI: 0.389–0.538 to κ = 0.681, 95% CI: 0.602–0.761). Agreement was consistently higher for radiographs not suggestive of pneumoconiosis, with agreement ranging from 85.9% to 94.4%. Across the four ILO profusion categories, substantial inter-reader agreement was observed, with linear weighted kappa ranging from (κ = 0.554, 95% CI: 0.483–0.625 to κ = 0.668, 95% CI: 0.598–0.739) and quadratic weighted kappa values ranging from (κ = 0.675, 95% CI: 0.604–0.747 to κ = 0.755, 95% CI: 0.685–0.826). Cross-tabulation analyses demonstrated that disagreement occurred predominantly between adjacent profusion categories. Category-specific analyses showed the highest concordance for Categories 0 and 3, while Category 1 demonstrated the poorest agreement, with κ values ranging from (κ = 0.091, 95% CI: 0.004–0.178 to κ = 0.216, 95% CI: 0.067–0.365). Inter-reader agreement was slightly higher among chest radiographs of ASGMs with previous tuberculosis treatment, with κ values ranging from (κ = 0.572, 95% CI: 0.360–0.784 to κ = 0.743, 95% CI: 0.565–0.921) than among those without with κ values ranging from (κ = 0.376, 95%C1: 0.291–0.460 to κ = 0.602, 95% C1: 0.498–0.706). These findings reflect substantial variability in classifying early or borderline pneumoconiotic changes. These findings highlight variability in radiographic interpretation and demonstrate the need for enhanced training, quality control, and consensus reading approaches in ASGMs’ screening programs. Full article

Over the past two decades, the world has experienced a significant and relentless increase in environmental degradation, measured through carbon emissions (CO₂). These emissions have been one of the persistent global concerns. South Africa boosts abundance of natural resources and some of the world’s most substantial mineral deposits, endowments in the form of precious metals, diamonds and gold. The paper aims to examine the impact of socio-economic and energy-related factors on environmental degradation from a South African perspective. Using multivariate annual data spanning from 1991 to 2022, the Autoregressive Distributed Lag Model (ARDL) was employed to determine both short-run and long-run impact of financial development (FD), renewable energy (RE), non-renewable energy (NRE), unemployment rate (UNE), economic growth (GDPPC), and population growth (PoPG) on CO₂ emission. The results show that NRE remains a dominant driver for environmental degradation, while RE is positively associated with emissions under current system conditions. FD exhibits short-run emission-intensity but long-run mitigation effects. The results suggest a need for relevant policymakers to prioritize coal displacement, stimulate economic growth and promote access to green financing, and related technologies and consumption, to enhance and promote environmental quality in South Africa. The conclusion is that South Africa’s energy-economy nexus is still at a transitional stage, where targeted policy intervention and structural reform are essential to accelerate the shift towards a low-emission economy. Future research can extend the analytical depth by exploring asymmetries, disaggregating fossil fuels, and incorporating broader environmental indicators. Full article

The Xiaoyinuogaigou (XYN) gold deposit is located in the central Erguna Metallogenic Belt, northeastern China, and represents a characteristic example of Mesozoic gold mineralization in the Mongol–Okhotsk orogenic province. Despite its economic significance, the timing of mineralization and the nature of the ore-forming fluid system have not been well constrained. To address these questions, a systematic investigation of fluid inclusions, isotopes, geochemistry, and geochronology was conducted. The study reveals that: (i) four types of fluid inclusions are identified in auriferous quartz veins, with co-existing aqueous liquid-vapor and NaCl daughter-mineral three-phase inclusions, indicating the involvement of at least two chemically distinct fluids; (ii) the ore-forming fluids are characterized by moderate temperatures (163.2–357.6 °C), low to moderate salinities (3.06–11.34 wt% NaCleqv.), and H–O isotope compositions (δD = −133.3 to −112.3‰; δ¹⁸O fluid (SMOW) = +1.74 to +4.06‰) consistent with a hydrothermal system incorporating a substantial non-magmatic water component; and (iii) REE geochemistry and sulfur isotopes (δ³⁴S = +4.47 to +11.75‰, mean +8.29‰, n = 4) indicate that ore-forming materials were derived at least in part from the ore-hosting granite porphyry. Zircon U–Pb geochronology constrains the granite porphyry crystallization to 180 ± 3 Ma, and hydrothermal monazite U–Pb dating yields an age of 162.3 ± 3.6 Ma (MSWD = 0.95), for a Middle Jurassic hydrothermal event. We therefore conclude that XYN is an epizonal orogenic gold deposit formed during the late compressional to post-collisional transition of the Mongol–Okhotsk orogeny. Full article

In open-pit mining, accurately mapping lithology, alteration, and mineralogy is vital for optimizing ore grade estimation, processing, and operational planning. Traditional geological pit-wall mapping is time-consuming, labor-intensive, and exposes technical staff to hazardous conditions. This study investigates a data-driven, hyperspectral classification workflow for pit-wall mapping at an open-pit gold mine. Three classification techniques were applied: Spectral Angle Mapper (SAM) using scene-derived reference spectra, Autoencoder + K-means (AE), and Band Ratio + K-means (BR), without relying on predefined training labels. Hyperspectral imagery was acquired using a tripod-mounted system integrating VNIR (400–1000 nm) and SWIR (970–2500 nm) sensors from two pit walls of contrasting geological complexity, with SWIR data driving primary mineral classification and VNIR data used separately for iron oxide mapping. Results were validated against laboratory hyperspectral scanning and XRD analyses of collected rock samples, as well as expert geological interpretation. Across both pit walls, Across both pit walls, SAM and BR produced closely consistent, geologically reliable classifications, with SAM showing the strongest correspondence to reference spectra and confirmed mineral assemblages; AE achieved comparable polygon-level agreement but with reduced mineralogical specificity, tending toward broader, less distinct class groupings. The study demonstrates that close-range tripod-based hyperspectral imaging with data-driven classification provides a practical, rapid alternative to manual pit-wall mapping, improving accuracy, reducing interpretation time, and minimizing personnel exposure to hazardous conditions. Full article

The Jiaoxibei gold cluster is one of the most significant gold-producing regions in China and retains substantial regional prospecting potential. However, the superposition of multiple mineralization events has resulted in strong spatial coupling, multi-scale variability, and substantial redundancy among structural, alteration, geophysical, and geochemical information, limiting the effective extraction of key ore-controlling features. This study developed a geologically constrained feature-engineering framework for regional mineral potential evaluation. An initial indicator system comprising 32 geologically meaningful factors was constructed from structural geometry, remote-sensing alteration, gravity, magnetic, and geochemical information. The previously developed SOMML method was extended by introducing borehole-derived geological constraints to construct G-SOMML and generate the comprehensive geochemical anomaly factor Chem_F. Correlation-based redundancy reduction, Random Forest importance evaluation, SHAP interpretation, and geological screening were then combined to identify nine core factors. The selected factors were subsequently transformed according to their mineralization-response directions and integrated through category-balanced fuzzy synthetic evaluation. By linking geology-guided feature construction, borehole-constrained geochemical anomaly extraction, data-driven feature diagnosis, and balanced evidence integration, the framework provides a reproducible and interpretable workflow for organizing heterogeneous geoscientific information in regional mineral potential evaluation. The resulting high-potential zones captured 21 of the 22 known gold occurrences in the Sanshandao and Jiaojia areas and 17 of the 23 occurrences in the other parts of the study area, yielding an overall deposit capture rate of 84.4%. Compared with the all-feature fuzzy synthetic evaluation model (AT-Fuzzy), feature engineering reduced the high-potential area ratio from 50.951% to 25.356% while increasing the deposit capture rate from 51.1% to 84.4%. At the map level, the proposed framework delineated a substantially smaller high-potential area than the Random Forest model while achieving higher deposit capture rates than both the Random Forest and Weights of Evidence models under the common evaluation domain and statistical thresholding criterion. These results support the applicability of the framework for interpretable regional mineral potential evaluation and target prioritization in complex metallogenic districts. Full article

Gold-vein deposits of the Nazca–Ocoña belt constitute an important economic resource for small- and medium-scale mining in Peru. However, the mineralogical and physicochemical controls governing gold distribution in these veins remain poorly understood. This study presents an integrated analysis of the Millonaria vein, San Juan de Chorunga, aimed at establishing the paragenetic sequence, characterizing the mode of occurrence of gold, and reconstructing the evolution of the hydrothermal fluids. Petrographic, ore microscopy, scanning electron microscopy, fluid inclusion microthermometry, and Au fire-assay data were integrated. The results indicate a main mineralizing stage, in which gold precipitated mainly in fractures and interstices of pyrite I and, subordinately, in microcavities within quartz I, as anhedral aggregates of native gold and electrum (Au ≈ 80%, Ag ≈ 20%). Specularite was also identified in fractures and interstices of pyrite I. A post-mineral substage I, characterized by milky quartz, carbonates, and subordinate sulfides, was also recognized, without significant gold precipitation. Fluid inclusions record homogenization temperatures of ~180–350 °C and low- to intermediate-salinity fluids (0.8–7.86 wt.% NaCl eq.). The data suggest at least two thermal contexts for gold mineralization, possibly influenced by dilution/mixing, local cooling, and redox changes. Full article

The newly discovered Caijiagou gold deposit is hosted in metasedimentary rocks of the Silurian Taiyangsi Formation in the West Qinling Orogen (WQO), central China. Three mineralization stages are recognized: (1) the quartz–sericite–pyrite stage (Stage I), characterized by fine-grained, disseminated pyrite (Py1) and arsenopyrite (Apy1) with trace amounts of native gold; (2) the main ore-stage, the quartz–polymetallic sulfide–ankerite stage (Stage II), which contains coarse-grained euhedral pyrite (Py2) and arsenopyrite (Apy2) intergrown with ankerite and native gold; and (3) the post-ore calcite stage (Stage III), which is barren. Hydrothermal alteration assemblages include silicification, sericitization, pyritization, and carbonatization. In situ trace element analyses show that gold is mainly hosted in Py2 (avg. 2.86 ppm Au) and Apy2 (avg. 1.95 ppm Au), with consistently low Co/Ni ratios (<0.6) in ore-stage sulfides, supporting a metamorphic fluid origin. Sulfur isotope values (δ³⁴S = +6.47‰ to +11.96‰) point to sulfur derived from thermochemical reduction of marine sulfate. Apatite from the main ore stage (Stage II) yields a U–Pb lower intercept age of 237 ± 4.3 Ma (MSWD = 0.89), placing the mineralization in the Middle Triassic (Indosinian orogeny). These results are consistent with a sediment-hosted orogenic gold model, and the geochemical and geochronological signatures provide insights into the ore-forming process and regional metallogeny of the WQO. Full article

The present work focuses on investigating U–Pb and Lu–Hf ages of zircon grains obtained from Au mineralized granitic rocks from Alta Floresta Gold Province (AFGP), in the Amazonia craton, Brazil. Also, detrital zircon grains from recent Au-rich sediments were analyzed for U–Pb ages and Lu–Hf isotopic signatures to apply to regional gold exploration in the AFGP to define targets consisting of deep-seated mineralized bodies using isotopic tracers. U–Pb ages of magmatic rocks, obtained from zircon grains, indicate crystallization ages ranging from 1896 Ma to 1825 Ma for rocks associated with gold deposits, and TDM model ages between 2.65 and 1.96 Ga and εHf values between +8.0 and −4.6. U–Pb ages obtained from 89 detrital zircon grains indicate peaks at 2055–1980 Ma, 1889–1985 Ma, 1790–1700 Ma, and 1600–1550 Ma. The first group is related to the basement, represented by the rocks of the Cuiu-Cuiu Complex (TDM 2.0–1.9 Ga and εHf from +8.7 to −1.32). The second group concerns the mineralized magmatic rocks in the AFPG, and the ages range from 18,896 to 1825 Ma, TDM ages ranging from 2.90 to 2.75 Ga, and the εHf values from +15 to −8. The age ranging from 1790 to 1700 is associated with anorogenic magmatism (TDM 2.0–1.9 Ga and εHf from +5.36 to −8.46). The youngest group comprises ages from 1600 to 1550 Ma, probably correlated to the Serra da Providencia suite with TDM of 1,6 to 1,50 Ga and εHf from +5,0 to −10. In this way, it was possible to identify the age range of detrital zircon grains concerning the ages of mineralized granites and characterize the Hf signatures associated with the mineralization processes. In this sense, the zircon grains associated with the magmatic processes responsible for the concentration of noble metals exhibited U–Pb ages and ε_Hf values interpreted as having been generated in magmas originating from a depleted mantle. As suggested in the literature, the magma characteristics reported here are coherent with a hot, hydrous, Fe-rich, high-K calc-alkaline, and subvolcanic emplacement. Based on the model that correlates gold deposits with porphyritic magmatic processes, significant discoveries with world-class volumes may result from better characterization of the deposit types found in the province. Full article

Sand enteropathy describes pathophysiological conditions of the equine gastrointestinal tract due to the uptake and accumulation of sand. It is an increasingly recognized cause of gastrointestinal disease in arid geographic areas. Clinical signs can vary widely from colic, fever and inappetence to poor performance. Diagnosis based solely on clinical signs is nearly impossible. The current literature describes a variety of diagnostic aids, with radiographic imaging considered the gold standard. Therapeutic approaches aim at the evacuation of sand from the abdomen. This can be achieved by the administration of psyllium in connection with a laxative via nasogastric intubation. Several studies describe varying laxatives such as mineral oil or sodium-/magnesium sulphate. This narrative review includes 39 publications up to the year 2026. We aim to raise awareness among practicing veterinarians and highlight new research objectives to improve knowledge and treatment of gastrointestinal diseases related to sand accumulation. Full article

The Shyngys–Tarbagatai folded system of Kazakhstan, located in the southwestern part of the Central Asian Orogenic Belt, represents a promising yet still insufficiently studied metallogenic region of Kazakhstan. The aim of the present study was to reassess its ore potential based on modern geotectonic concepts and a comprehensive metallogenic analysis. An evaluation of the ore potential of nine structural–formational zones was carried out, and their metallogenic specialization was determined. The dominant role of gold and copper mineralization was established, along with the features of spatial distribution of ore occurrences and the most promising areas for further exploration. It was shown that the most ore-rich stratigraphic levels include the Early Cambrian, Late Ordovician, Early Silurian, Early Devonian, and Late Devonian units. It was demonstrated that the formation of the main ore types is closely related to productive geodynamic settings, including Early Paleozoic oceanic rifts, island-arc complexes, and the Devonian continental-margin volcano-plutonic belt. Based on the obtained results, a map of prospective areas at a scale of 1:1,500,000 was compiled, and these areas were ranked according to their degree of prospectivity. A total of 51 targets were identified as priority sites for follow-up prospecting, evaluation, and detailed exploration work. Full article

PhotonAssay™ is a rapid, non-destructive gold assay method that analyses large-mass crushed or pulverised samples while reducing turnaround time, hazardous reagent use, and environmental footprint relative to conventional fire assay. Its growing adoption, however, has exposed a persistent misconception, that CRIRSCO-based reporting codes approve certain analytical methods as being “compliant.” This paper clarifies the reporting position for PhotonAssay™ and outlines the key requirements for its use in Exploration Results, Mineral Resource, and Ore/Mineral Reserve reporting, including sampling context, preparation protocol, quality assurance/quality control and method validation. It also frames adoption as a four-stage journey—awareness, consideration, intent, and implementation—in which peer learning, testwork, business-case development, and deployment planning are as important as analytical performance. Particular attention is given to representative sampling and to interpreting differences from fire assay, especially in coarse-gold systems where larger assay charges are likely to yield more representative results. Two test methods are recommended, the transitional feasibility study (bias between assay methods) and heterogeneity study (bias and precision). The PhotonAssay™ adoption journey is a multidisciplinary process, requiring engagement between practitioners and executives, and between geoscientists, mining and minerals engineers, chemists, data scientists and corporate managers. Full article