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We present results from a natural deformed shear zone in the Turon de Técouère massif of the French Pyrenees that directly addresses the processes involved in strain localization, a topic that has been investigated for the last 40 years by structural geologists. Paleopiezometry indicates that differential stresses are variable both spatially across the zone, and temporally during exhumation. We have, however, also calculated strain rate, which remains constant despite changes in stress. This result appears to be at odds with recent experimental deformation on monophase (olivine) rocks, which indicate that strain localization occurs dominantly as a result of constant stress. We hypothesize that in the Turon de Técouère massif—and many natural shear zones—strain localization occurs as a result of reactions, which decrease the grain size and promote the activation of grain size sensitive deformation mechanisms. From a tectonics perspective, this study indicates that the deformation rate in a particular plate boundary is relatively uniform. Stress, however, varies to accommodate this deformation. This viewpoint is consistent with deformation at a plate boundary, but it is not the typical way in which we interpret strain localization.

Shear-induced polymer-bridging flocculation is widely used in the solid–liquid separation process in cemented paste backfill, beneficial to water recycling and tailings management in metal mines. A flocculation kinetics model based on Population Balance Model (PBM) is proposed to model the polymer-bridging flocculation process of total tailings. The PBM leads to a system of ordinary differential equations describing the evolution of the size distribution, and incorporates an aggregation kernel and a breakage kernel. In the aggregation kernel, a collision frequency model describes the particle collision under the combined effects of Brownian motions, shear flow, and differential sedimentation. A semi-empirical collision efficiency model with three fitting parameters is applied. In the breakage kernel, a new breakage rate coefficient model with another three fitting parameters is introduced. Values of the six fitting parameters are determined by minimizing the difference between experimental data obtained from FBRM and modeling result through particle swarm global optimization. All of the six fitting parameters vary with flocculation conditions. The six fitting parameters are regressed with the flocculation factors with six regression models obtained. The validation modeling demonstrates that the proposed PBM quantifies well the dynamic evolution of the floc size during flocculation under the given experimental setup. The investigation will provide significant new insights into the flocculation kinetics of total tailings and lay a foundation for studying the performance of the feedwell of a gravity thickener.

Nickel metal hydride (NiMH) batteries are extensively used in the manufacturing of portable electronic devices as well as electric vehicles due to their specific properties including high energy density, precise volume, resistance to overcharge, etc. These NiMH batteries contain significant amounts of rare earth metals (REMs) along with Co and Ni which are discarded due to illegal dumping and improper recycling practices. In view of their strategic, economic, and industrial importance, and to mitigate the demand and supply gap of REMs and the limited availability of natural resources, it is necessary to explore secondary resources of REMs. Therefore, the present paper reports a feasible hydrometallurgical process flowsheet for the recovery of REMs and valuable metals from spent NiMH batteries. More than 90% dissolution of REMs (Nd, Ce and La) was achieved using 2 M H2SO4 at 75 °C in 60 min in the presence of 10% H2O2 (v/v). From the obtained leach liquor, the REMs, such as Nd and Ce, were recovered using 10% PC88A diluted in kerosene at eq. pH 1.5 and O/A ratio 1/1 in two stages of counter current extraction. La of 99% purity was selectively precipitated from the leach liquor in the pH range of 1.5 to 2.0, leaving Cu, Ni and Co in the filtrate. Further, Cu and Ni were extracted with LIX 84 at equilibrium pH 2.5 and 5, leaving Co in the raffinate. The developed process flow sheet is feasible and has potential for industrial exploitation after scale-up/pilot trails.

The effects and mechanism of magnetized kerosene on the flotation behaviors of molybdenite were studied by micro-flotation, ultraviolet spectrum, infrared spectrum, surface tension, and liquid viscosity. According to the results of micro-flotation, magnetized kerosene improved the flotation recovery of molybdenite, and the improvements were more obvious with smaller molybdenite particles. Spectral analysis showed that the magnetization did not change the chemical composition of kerosene, but transformed the linear aliphatic hydrocarbons in kerosene into linear isomers and reduced the lengths of the carbon chains. Moreover, the magnetization reduced the viscosity of kerosene and oil/water interfacial tension, and improved the dispersion of kerosene in the pulp. The external magnetic field transformed the disorder of the additional magnetic moment in the kerosene molecules into order, and reduced the compactness of the kerosene molecules. The experimental results provided a theoretical explanation for the role of magnetization in mineral flotation.

Modelling of 3D domain boundaries using information from drill holes is a standard procedure in mineral exploration and mining. Manual logging of drill holes can be difficult to exploit as the results may not be comparable between holes due to the subjective nature of geological logging. Exploration and mining companies commonly collect geochemical or mineralogical data from diamond drill core or drill chips; however, manual interpretation of multivariate data can be slow and challenging; therefore, automation of any of the steps in the interpretation process would be valuable. Hyperspectral analysis of drill chips provides a relatively inexpensive method of collecting very detailed information rapidly and consistently. However, the challenge of such data is the high dimensionality of the data’s variables in comparison to the number of samples. Hyperspectral data is usually processed to produce mineral abundances generally involving a range of assumptions. This paper presents the results of testing a new fast and objective methodology to identify the lithological boundaries from high dimensional hyperspectral data. This method applies a quadrant scan analysis to recurrence plots. The results, applied to nickel laterite deposits from New Caledonia, demonstrate that this method can identify transitions in the downhole data. These are interpreted as reflecting mineralogical changes that can be used as an aid in geological logging to improve boundary detection.

The cone crusher is the main equipment in the particle crushing process. The productivity of the cone crusher is determined by the motion characteristics of particles passing through the crushing chamber. In order to accurately describe the motion characteristics of the particles, the influence of the spatial compound motion of the mantle rotates around the central axis of the cone crusher and its central axis on the motion characteristics of the particles is investigated, then the improved motion model is established. Through the coordinate system transformation matrix, the motion characteristics of the particles including spatial sliding, free-falling, and spatial compound falling are solved. The applicability and accuracy of the improved model in describing the motion characteristics of the particle were verified through the experiment using a reduced-scale experimental cone crusher to simulate the motion characteristics of the particle. Based on the improved model, the motion characteristics of the particles in the CF11 hydraulic cone crusher can be simulated. With the decrease in height, the motion characteristics of particles gradually change from spatial sliding to spatial compound falling and finally to free-falling. The particles deflect circumferentially around the central axis of the cone crusher. The circumferential deflection of particles is directly related to the motion characteristics including spatial sliding and spatial compound falling. The improved model provides a theoretical basis for the high energy design of the crushing chamber and productivity improvement of the cone crusher.

The study area is located in the old mining district of Linares–La Carolina (southeastern Spain), the largest global producer of lead between 1875 and 1920. The selected environmental liability is the dam of the Federico mine and the waste that was generated during the flotation process. Geophysical techniques were applied along the slope of the dam, specifically ERT and IP. In total, 26 waste samples were taken along the entire slope of the dam, in which a high metal(oid) content was identified, sometimes much higher than the reference levels established by European and regional legislation for contaminated soils. The concentrations of Pb, As, and Ba stood out, with mean values of 4863 mg·kg−1, 89 mg·kg−1, and 794 mg·kg−1, respectively. Univariate and multivariate statistical analysis could characterize the distribution of the contents of the different elements along the slope, defining the associations and dispersion patterns of the metal(oid)s in the interior structure of the mine wastes. With the results of the Pb content (the most abundant metal in mineral paragenesis), a mathematical model was obtained by linear regression that related the variability of this cation with the variation in electrical resistivity and chargeability obtained by geophysical techniques.

Minerals 12(1), 19 (2022). doi:10.3390/min12010019 special issue: "Special Issue "Valorization of Metallurgical and Mining Residues and Wastes" / special issue editors: Prof. Dr. George Angelopoulos, guest editor; Prof. Dr. Luis P��rez Villarejo, guest editor", Published by MDPI, Basel

Currently, Luzhou in the Sichuan Basin is a focal point for shale-gas exploration and development in China. However, a lack of detailed research on the mineral composition of the Wufeng Formation-Longmaxi Formation (WF-LF) shale is hindering the extraction of deep-buried shale gas in the Luzhou shale play. Herein, a field emission scanning electron microscope (FESEM) equipped with the Advanced Mineral Identification and Characterization System (AMICS) software was employed to analyze the mineral composition of the WF-LF shale from six wells in Luzhou. Quartz was the dominant mineral type, (16.9–87.21%, average 51.33%), followed by illite, calcite, dolomite, and pyrite. Our study revealed that (1) quartz content showed a moderate positive correlation with the total organic carbon (TOC) content, indicating that the quartz found in the shale is mostly of biological origin; and (2) the sum content of siliceous minerals and carbonaceous minerals was moderately positively correlated with the brittleness index (BRIT) in well SS1H2-7 and in the well group of RS8 and RS5, indicating that the siliceous minerals and carbonaceous minerals had an active effect on reservoir compressibility. Finally, according to the mineralogical features of each sublayer, we identified four types of reservoirs to determine their scope for exploration.

The CIECAM16 colour appearance model is currently a model with high prediction accuracy. It can solve the problem of predicting the influence of different observation conditions on the colour of gemstones. In this study, a computer vision system (CVS) was used to measure the colour of 59 bluish-green serpentinite samples, and the tristimulus values were input into the CIECAM16 forward model to calculate the colour appearance parameters of serpentinite under different surrounds, illuminances, and light sources. It was found that the darkening of the surround causes the lightness and brightness to increase. Pearson’s r of brightness and colourfulness with illuminance is 0.885 and 0.332, respectively, which predicts the Stevens and Hunt effects. When the light source changes from D65 to A, the calculated hue angle shifts to the complementary area of the A light source, which is contrary to the CVS measurement result. The D65 light source is more suitable for the colour presentation and classification of bluish-green serpentinite.

Cobalt (Co) mine production primarily originates from the sediment-hosted copper (Cu) deposits of the Democratic Republic of Congo (DRC). These deposits usually consist of three ore zones with a supergene oxide ore blanket overlying a transition zone which grades into a sulphide zone at depth. Each of these zones display a mineral assemblage with varying gangue mineralogy and, most importantly, a distinct state of oxidation of the mineralisation. This has direct implications for Cu and Co extraction during mineral processing as it dictates which processing method is to be used (i.e., leaching vs. flotation) and affects the performance of these. To optimise resource efficiency, reduce technical risks and environmental impacts, comprehensive understanding of variation of ore mineralogy and texture in the deposit is essential. By defining geometallurgical ore types according to their inferred metallurgical behaviour, this information can serve to classify the resources and improve resource management. To obtain insight into the spatial distribution of mineral grades, it is necessary to develop techniques that have the potential to measure rapidly and, preferably, within the mine at relatively low-cost. In this study, the application of portable Fourier transformed infrared (FTIR) spectroscopy is investigated to measure the mineralogy of drill core samples. A set of samples from a sediment-hosted Cu-Co deposit in DRC was selected to test this approach. Results were validated using automated mineralogy (QEMSCAN). Prediction of gangue and target mineral grades from the FTIR spectra was achieved through partial least squares regression (PLS-R) combined with competitive adaptive reweighted sampling (CARS). It is shown that the modal mineralogy obtained from FTIR can be used to classify the ore according to type of mineralisation and gangue mineralogy into geometallurgical ore types. This classification supports selection of a suitable processing route and is likely to affect the overall process performance.

Sulfur contents in 98.5% of melt inclusions (MI) from calc-alkaline subduction basalts do not exceed 4000 ppm, whereas experimentally established limits of sulfur solubility in basaltic melts with high fO2 (characteristic of subduction zones, e.g., QFM + 2) surpass 14,000 ppm. Here we show that primitive (Mg# 62-64) subduction melts may contain high sulfur, approaching the experimental limit of sulfur solubility. Up to 11,700 ppm S was measured in olivine-hosted MI from primitive arc basalt from the 1941 eruption of the Tolbachik volcano, Kamchatka. These MI often contain magmatic sulfide globules (occasionally enriched in Cu, Ni, and platinum-group elements) and anhydrite enclosed within a brown, oxidized glass. We conclude that the ubiquitous low sulfur contents in MI may originate either from insufficient availability of sulfur in the magma generation zone or early magma degassing prior to inclusion entrapment. Our findings extend the measured range of sulfur concentrations in primitive calc-alkaline basaltic melts and demonstrate that no fundamental limit of 4000 ppm S exists for relatively oxidized subduction basalts, where the maximum sulfur content may approach the solubility limit determined by crystallization of magmatic anhydrite.

The evolution characteristics of hydrothermal activity and superimposed uranium mineralization in the Qianjiadian ore field in southwestern Songliao Basin are still controversial and lack direct evidence. In this comprehensive study, a detailed identification of dolerite and hydrothermally altered un-mineralized sandstone and sandstone-hosted ore in the Yaojia Formation have been performed through the use of scanning electron microscopy observation, electron probe, carbon-oxygen-sulfur isotope, and fluid inclusion analyses. The results show that the hydrothermal fluid derived from the intermediate-basic magma intrusion is a low-temperature reducing alkaline fluid and rich in CO2, Si, Zr, Ti, Fe, Mg, Mn, and Ca, producing different types of altered mineral assemblages in the rocks, including carbonation, pyritization, sphalerite mineralization, clausthalite mineralization, silicification, and biotitization. Specifically, the carbonate minerals in sandstone are mixed products of deep hydrothermal fluid and meteoric water, with carbon and oxygen isotopes ranging from −5.2‰ to −1.7‰ and −20.4‰ to −11.1‰, respectively. Carbon source of the carbonate minerals in dolerite is mainly inorganic carbon produced at the late stage of intermediate-basic magma evolution, with carbon and oxygen isotopes from −16.1‰ to −7.2‰ and −18.2‰ to −14.5‰, respectively. Various carbonate minerals in the rocks may have been precipitated by the hydrothermal fluid after the magmatic stage, due to the change of its CO2 fugacity, temperature, and cation concentration during the long-term evolution stage. A series of carbonate minerals were generated as calcite, dolomite, ankerite, ferromanganese dolomite, and dawsonite. The precipitation processes and different types of carbonate mineral mixtures identified in this study mainly occur as parallel, gradual transition, interlacing, or inclusion metasomatism in the same vein body, without obvious mineralogical and petrologic characteristics of penetrating relationship. Homogenization temperature of fluid inclusions in calcite is high, in the range of 203–234 °C, with a low salinity of 0.71–4.34% NaCl, and the data range is relatively concentrated. Homogenization temperature of fluid inclusions in ankerite is usually low, ranging from 100 °C to 232 °C, with a high salinity of 4.18–9.98% NaCl. The precipitation processes of carbonate minerals and the results of this study are basically in consistent. Overall, the sandstone-type uranium deposits have a temporal and genetic relationship with hydrothermal activities during Paleogene. (1) Hydrothermal activity was directly involved in uranium mineralization, result in dissolution and reprecipitation of earlier uranium minerals, forming uranium-bearing ankerite and complexes containing uranium, zirconium, silicon, and titanium. (2) Hydrothermal fluid activity provided reducing agent to promote hydrocarbon generation from pyrolysis of carbonaceous fragments and accelerate uranium precipitation rate. (3) Regional water stagnation prolongs reaction time, contributing to huge uranium enrichment. This study provides new petrologic, mineralogical, and geochemical evidence for multi-fluid coupled and superimposed mineralization of sandstone-hosted uranium deposits in the sedimentary basin.

Scheelitization of Mn-bearing wolframite, scheelite, quartz, and Fe,Mn-chlorite veins was identified in the W, (Cu,Mo) ore deposits of Borralha, by optical microscopy, electron-microprobe analysis, and stable isotope geochemistry. Fluid inclusions derived scheelite crystallization temperature was compared with the oxygen isotope temperature estimated. Scheelite was formed mainly during stage I from a low salinity aqueous-carbonic fluid dominated by CO2, where the homogenization temperature (Th) decreased from 380 °C to 200 °C (average of 284 °C). As temperature decreased further, the aqueous-carbonic fluid became dominated by CH4 (Stage II; (average Th = 262 °C)). The final stage III corresponds to lower temperature mineralizing aqueous fluid (average Th = 218 °C). In addition, salinity gradually decreased from 4.8 wt.% to 1.12 wt.%. The δ18OFluid values calculated for quartz-water and wolframite-water fractionation fall within the calculated magmatic water range. The ∆quartz-scheelite fractionation occurred at about 350–400 °C. The ∆chlorite-water fractionation factor calculated is about +0.05‰ for 330 °C, dropping to −0.68‰ and −1.26‰ at 380 °C and 450 °C, respectively. Estimated crystallizing temperatures based on semi-empirical chlorite geothermometers range from 373 °C to 458 °C and 435 °C to 519 °C. A narrower temperature range of 375 °C to 410 °C was estimated for Fe,Mn-chlorite crystallization.

Focusing on the selective extraction of the critical raw materials indium and germanium from real bioleaching solutions, extended studies have been carried out using Europe’s first underground hybrid membrane pilot plant (TRL6). In order to transfer former laboratory experiments to pilot scale, NF99 (Alfa Laval) was used for the evaluation of membrane permeance and ion retention. A performance test of microfiltration (MF) and nanofiltration (NF) showed high permeances with low root-mean-square deviation under feed variation (5.2% for MF, 4.7% for NF). Depending on the feed load, a significant permeance drop of up to 57% for MF (3 bar) and 26% for NF (10 bar, 1.1 m s−1) was observed. The NF retention performance showed that, without regular chemical cleaning, the selectivity between the target elements degraded. By introducing acidic-basic cleaning steps, it was possible to keep the retention behavior at an approximately constant level (In 91.0 ± 1.3%; Ge 18.2 ± 5.5%). In relation to the specified target, the best results could be achieved at low pressure (7.5 bar) and a maximum overflow velocity of 1.1 m s−1, with a retention of 88.4% for indium and 8.8% for germanium. Moreover, the investigations proved the functionality and long-term stability of the underground membrane device.

Seawater has been increasingly used as an alternative to freshwater in mineral flotation. Although previous studies suggest that Mg2+ ions in seawater have the primary negative roles in chalcopyrite flotation, insufficient work has been conducted to understand the effects of kerosene as a collector in chalcopyrite flotation. In this study, the influence of kerosene emulsion on chalcopyrite floatability in a solution containing Mg2+ was systematically investigated. The results indicated that the addition of kerosene significantly reduced the adsorption of hydrophilic Mg-precipitates onto the chalcopyrite’s surface. In addition to contact angle, zeta potential, optical microscopy, and Fourier-transform infrared spectroscopy analyses, extended Derjguin–Landau–Verwey–Overbeek (EDLVO) theory and density functional theory (DFT) calculations were conducted to understand the influencing mechanisms of kerosene on chalcopyrite flotation. The adsorption energies showed an order of kerosene and Mg(OH)2 > kerosene and chalcopyrite > chalcopyrite and Mg(OH)2, indicating kerosene was preferentially adsorbed on the Mg(OH)2 surface, forming agglomerates and therefore reducing the adsorption of Mg(OH)2 precipitates onto the chalcopyrite’s surface. In addition, hydrophobic agglomerates were also formed due to the attachment of kerosene to the chalcopyrite’s surface when additional kerosene was added, further enhancing chalcopyrite floatability.

Calcium oxalates are naturally occurring biominerals and can be found as a byproduct of some industrial processes. Recently, a new and green method for carbon capture and sequestration in stable calcium oxalate from oxalic acid produced by carbon dioxide reduction was proposed. The reaction resulted in high-quality weddellite crystals. Assessing the stability of these weddellite crystals is crucial to forecast their reuse as solid-state reservoir of pure CO2 and CaO in a circular economy perspective or, eventually, their disposal. The thermal decomposition of weddellite obtained from the new method of carbon capture and storage was studied by coupling in-situ high-temperature X-ray powder diffraction and thermogravimetric analysis, in order to evaluate the dehydration, decarbonation, and the possible production of unwanted volatile species during heating. At low temperature (119–255 °C), structural water release was superimposed to an early CO2 feeble evolution, resulting in a water-carbon dioxide mixture that should be separated for reuse. Furthermore, the storage temperature limit must be considered bearing in mind this CO2 release low-temperature event. In the range 390–550 °C, a two-component mixture of carbon monoxide and dioxide is evolved, requiring oxidation of the former or gas separation to reuse pure gases. Finally, the last decarbonation reaction produced pure CO2 starting from 550 °C.

In the Dingwall gypsum quarry in Nova Scotia, Canada, operating in 1933–1955, the bedrock anhydrite deposits of the Carboniferous Windsor Group have been uncovered from beneath the secondary gypsum beds of the extracted raw material. The anhydrite has been subjected to weathering undergoing hydration (gypsification), transforming into secondary gypsum due to contact with water of meteoric derivation. The ongoing gypsification is associated with a volume increase and deformation of the quarry bottom. The surface layer of the rocks is locally split from the substrate and raised, forming spectacular hydration relief. It shows numerous domes, ridges and tepee structures with empty internal chambers, some of which represent unique hydration caves (swelling caves, Quellungshöhlen). The petrographic structure of the weathering zone has been revealed by macro- and microscopic observations. It was recognized that gypsification commonly starts from a developing network of tiny fractures penetrating massive anhydrite. The gypsification advances from the fractures towards the interior of the anhydrite rocks, which are subdivided into blocks or nodules similar to corestones. Characteristic zones can be recognized at the contact of the anhydrite and the secondary gypsum: (1) massive and/or microporous anhydrite, (2) anhydrite penetrated by tiny gypsum veinlets separating the disturbed crystals and their fragments (commonly along cleavage planes), (3) gypsum with scattered anhydrite relics, and (4) secondary gypsum. The secondary gypsum crystals grow both by replacement and displacement, and also as cement. Displacive growth, evidenced by abundant deformation of the fragmented anhydrite crystals, is the direct cause of the volume increase. Crystallization pressure exerted by gypsum growth is thought to be the main factor generating volume increase and, consequently, also the formation of new fractures allowing water access to “fresh” massive anhydrite and thus accelerating its further hydration. The expansive hydration is taking place within temperature range from 0 to ~30 °C in which the solubility of gypsum is lower than that of anhydrite. In such conditions, dissolving anhydrite yields a solution supersaturated with gypsum and the dissolution of anhydrite is simultaneous with in situ replacive gypsum crystallization. Accompanying displacive growth leads to volume increase in the poorly confined environment of the weathering zone that is susceptible to upward expansion.

The platinum-group minerals (PGM) in placer deposits provide important information on the types of their primary source rocks and ores and formation and alteration conditions. The article shows for the first time the results of a study of placer platinum mineralization found in the upper reaches of the Kitoy River (the southeastern part of the Eastern Sayan (SEPES)). Using modern methods of analysis (scanning electron microscopy), the authors studied the microtextural features of platinum-group minerals (PGM), their composition, texture, morphology and composition of microinclusions, rims, and other types of changes. The PGM are Os-Ir-Ru alloys with a pronounced ruthenium trend. Many of the Os-Ir-Ru grains have porous, fractured, or altered rims that contain secondary PGE sulfides, arsenides, sulfarsenides, Ir-Ni-Fe alloys, and rarer selenides, arsenoselenides, and tellurides of the PGE. The data obtained made it possible to identify the root sources of PGM in the placer and to make assumptions about the stages of transformation of primary igneous Os-Ir-Ru alloys from bedrock to placer. We assume that there are several stages of alteration of high-temperature Os-Ir-Ru alloys. The late magmatic stage is associated with the effect of fluid-saturated residual melt enriched with S, As. The post-magmatic hydrothermal stage (under conditions of changing reducing conditions to oxidative ones) is associated with the formation of telluro-selenides and oxide phases of PGE. The preservation of poorly rounded and unrounded PGM grains in the placer suggests a short transport from their primary source. The source of the platinum-group minerals from the Kitoy River placer is the rocks of the Southern ophiolite branch of SEPES and, in particular, the southern plate of the Ospa-Kitoy ophiolite complex, and primarily chromitites.

The galvanic interaction between chalcopyrite and monoclinic pyrrhotite and its effect on flotation separation were studied using monomineral flotation tests, adsorption capacity tests, X-ray photoelectron spectroscopy (XPS) characterization, and scanning electron microscopy (SEM) test. These results showed that the interaction promoted the reduction of O2 on the cathodic chalcopyrite surface and accelerated the generation of Fe(OH)3, which was not conducive to collector adsorption; hence, the flotation recovery decreased by 10–16%. On the other hand, galvanic interaction accelerated the oxidation of S on the anodic monoclinic pyrrhotite surface to S0 or SO42− and produced a large amount of H+, thus preventing the formation of Fe(OH)3. Meanwhile, the Cu2+ eluted from chalcopyrite surface activated monoclinic pyrrhotite; hence, the flotation recovery increased by 3–10%. Galvanic interaction reduced the floatability difference between the two minerals, and the separation difficulty was significantly increased. Even with an increase in the amount of lime, the separation could not be improved.

Glass ionomer cement (GIC) or polyalkenoate cement is a water-based cement that is commonly used in clinical dentistry procedures as a restorative material. It exhibits great properties such as fluoride-ion release, good biocompatibility, ease of use and great osteoconductive properties. However, GIC’s low mechanical properties have become a major drawback, limiting the cement’s usage, especially in high stress-bearing areas. Nanohydroxyapatite, which is a biologically active phosphate ceramic, is added as a specific filler into glass ionomer cement to improve its properties. In this review, it is shown that incorporating hydroxyapatite nanoparticles (nHA) into GIC has been proven to exhibit better physical properties, such as increasing the compressive strength and fracture toughness. It has also been shown that the addition of nanohydroxyapatite into GIC reduces cytotoxicity and microleakage, whilst heightening its fluoride ion release and antibacterial properties. This review aims to provide a brief overview of the recent studies elucidating their recommendations which are linked to the benefits of incorporating hydroxyapatite nanoparticles into glass ionomer cement.

Air pollution is monitored mainly in urban or industrial areas, even if it is known that in rural ones, low emission can significantly worsen air quality. Hence, cheap and easily accessible methods of monitoring are needed. Recently, spider webs biomonitoring is getting popular, however, there is no information about its comparison with active methods. In this study, PTEs accumulated on spider webs were compared with results from continuous particulate monitor (CPM). Generally, higher potentially toxic elements concentrations were noted in spider web, with exception in the case of Zn. Zn may be present rather in smaller fractions, hence it needs more time for accumulation on spider web while it is easily collected by CPM. Higher concentrations of other elements on spider webs may result from formation of aggregates which could not be reported in PM10 sampling (CPM). What is more, the order of the most and the least accumulated elements were similar and the percentage share of studied elements was coherent in most cases, proving that this new tool prospers to become commonly used in biomonitoring. Additionally, to identify possible sources of pollution air backward trajectories and trajectory frequencies for Kotórz were prepared based on the HYSPLIT model.

One of the main problems in current flotation plants and new projects is the significant decrease in feed grades and changes in the mineral composition, which has an important effect on the mineral liberation and associations. Additionally, flotation plants usually operate with a feed throughput higher than the original design, which has a significant impact on the feed particle size. All these conditions affect the metallurgical performance, and they must be evaluated and addressed by improving the control strategies for the optimization of banks. For this purpose, the flotation of valuable minerals along the circuits requires better understanding, considering the compromise between performance and selectivity in flotation circuits. This paper presents a characterization of the different minerals recovered along industrial flotation circuits. Plant sampling campaigns, performed in a copper industrial concentrator in Chile, provided the data for the study. Two rougher flotation banks consisting of cells of 130 m3 and 300 m3, were evaluated. All the samples from the industrial surveys were analysed by screening and mineralogy, and the mineral recovery along the circuits was evaluated per particle size class, liberation class, type of associations, and others. Additionally, operating data on froth depth profiles complemented the evaluation of the mineral composition of concentrate streams along the circuit. The results allowed for identifying and quantifying the main factors that affect the copper recovery and concentrate grade along the flotation banks. We found that minerals with liberation lower than 50% have a significant impact on the recovery. On the other hand, the decrease in the Cu grade in concentrates along the flotation circuits is mainly due to the relative increase of middling minerals (less liberated), non-valuable floatable minerals, such as free pyrite, and gangue entrainment. The characterization of the gangue entrainment flowrate along the flotation banks showed a strong relationship with froth depth, which becomes more critical towards the last cells of the banks.

Quartz is one of the most common minerals in soils, mostly present in sand and silt fractions. Although quartz is basically formed of SiO2, other elements can be easily detected and assessed nowadays using a portable X-ray fluorescence (pXRF) spectrometer. Our study aims to evaluate the chemical composition of different quartz varieties, identifying their main elements, and relating them to soil attributes. Six quartz varieties (hyaline, amethyst, milky, rose, smoky, and ferriferous) were analyzed via pXRF and 13 oxides/trace elements were identified and used for quartz discrimination (Al2O3, CaO, P2O5, SiO2, Cl, Cr, Fe, K2O, Mn, Rb, S, Ti, and V). Hyaline quartz was characterized by the highest SiO2 and the lowest contents of other elements. Al2O3 was the second-highest compound present in all varieties of quartz, reaching 21,547 mg kg−1 in the smoky variety. S, P2O5, Cl, SiO2, and K2O were the main components determined by Random Forest algorithm for discriminating quartz varieties. Some elements detected may serve as a reserve of nutrients to plants to be released in soils along weathering, depending on quartz particle size, soil texture, leaching, and associated attributes. pXRF enhanced the information on chemical characterization of quartz varieties, without the generation of chemical pollutants.

Accurately determining rock elastic modulus (EM) and uniaxial compressive strength (UCS) using laboratory methods requires considerable time and cost. Hence, the development of models for estimating the mechanical properties of rock is a very attractive alternative. The current research was conducted to predict the UCS and EM of sandstone rocks using quartz%, feldspar%, fragments%, compressional wave velocity (PW), the Schmidt hardness number (SN), porosity, density, and water absorption via simple regression, multivariate regression (MVR), K-nearest neighbor (KNN), support vector regression (SVR) with a radial basis function, the adaptive neuro-fuzzy inference system (ANFIS) using the Gaussian membership (GM) function, and the back-propagation neural network (BPNN) based on various training algorithms. The samples were categorized as litharenite and feldspathic litharenite. By increasing the feldspar% and quartz% and decreasing the fragments%, the static properties increased. The results of the statistical analysis showed that the SN and porosity have the greatest effect on the UCS and EM, respectively. Among the Levenberg–Marquardt (LM), Bayesian regularization, and Scaled Conjugate Gradient training algorithms using the BPNN method, the LM achieved the best results in forecasting the UCS and EM. The ideal obtained BPNN, using a trial-and-error process, contains four neurons in a hidden layer with eight inputs. All five models attained acceptable accuracy (correlation coefficient greater than 70%) for estimating the static properties. By comparing the methods, the ANFIS showed higher precision than the other methods. The UCS and EM of the samples can be determined with very high accuracy (R2 > 99%).

Saudi Arabia covers most of the Arabian Peninsula and is characterized by tectonic regimes ranging from Precambrian to Recent. Using gravity data to produce the lateral boundaries of subsurface density bodies, and edge detection of potential field data, a new subsurface structural map was created to decipher the structural framework controls on the distribution of gold deposits in Saudi Arabia. Moreover, we detected the relationships between major structures and mineral accumulations, thereby simultaneously solving the problem of edge detectors over complex tectonic patterns for both deeper and shallower origins. Analytic signal (ASg), theta map (TM), TDX, and softsign function (SF) filters were applied to gravity data of Saudi Arabia. The results unveil low connectivity along the Najd fault system (NFS) with depth, except perhaps for the central zones along each segment. The central zones are the location of significant gold mineralization, i.e., Fawarah, Gariat Avala, Hamdah, and Ghadarah. Moreover, major fault zones parallel to the Red Sea extend northward from the south, and their connectivity increases with depth and controls numerous gold mines, i.e., Jadmah, Wadi Bidah, Mamilah, and Wadi Leif. These fault zones intersect the NFS in the Midyan Terrane at the northern part of the AS, and their conjugation is suggested to be favorable for gold mineralization. The SF maps revealed the boundary between the Arabian Shield and Arabian Shelf, which comprises major shear zones, implying that most known mineralization sites are linked to post-accretionary structures and are not limited to the Najd fault system (NFS).

Currently, the high demand for copper is in direct contrast with the decrease in the mineral grade and, more significantly, the concerns regarding the environmental impact that arise as a result of processing such low-grade materials. Consequently, new mineral processing concepts are needed. This work explores the chemical dissolution of chalcopyrite concentrate at ambient pressure and moderate temperatures in a deep eutectic solvent. Copper and iron are dissolved without changing their oxidation state, without solvent pH change, and stabilized as a chloride complex with no evidence of passivation. Chemical equilibria of the metallic chloride complexes limit the dissolution, and the step that is rate-controlling of the kinetics is the interdiffusion of species in the solvent. The chemical mechanism may involve initial chloride adsorption at positive sites of the solid surface, pointing out the importance of surfaces states on chalcopyrite particles. A model based on a shrinking particle coupled with pseudo-second-order increase in the liquid concentration of copper describes the dissolution kinetics and demonstrates the importance of the liquid to solid ratio. Iron and copper can be recovered separately from the solvent, which highlights that this concept is an interesting alternative to both redox-hydrometallurgy and pyrometallurgy to obtain copper by the processing of chalcopyrite concentrate.

Meso-structure is an important factor affecting the characteristics of rock fracture. To determine the factors influencing the internal meso-structural characteristics upon the crack generation and extension, rock samples were tested under uniaxial cyclic loading and unloading and examined using computed tomography (CT) scanning. CT scanning was used to visualize and investigate the entire process of fracture source generation and its development in three dimensions, and finally the location information of the fracture source was determined. The mineral composition and structure along the fracture path inside the specimen were studied by using a polarizing microscope, and the evolution of fracture propagation around mineral particles was revealed based on its mineralogical characteristics. Results indicate that based on the fracture source around different rock meso-structure types, the initial fracture source can also be divided into different types, namely, the primary porosity type, the micro-crack type, and the mineral grain type. The strength characteristics of mineral grains can determine whether the crack extends around the gravel or through it. The hard grains at the crack-tip promote the transformation of tensile stress to shear stress, which lead to the change in the direction of crack extension and bifurcation. The spatial shape of the cracks after rock fracture is related to the initial distribution of minerals and is more complicated in areas where minerals are concentrated. The crack extension around gravel particles also generates a mode of failure, affecting large grains with gravel spalling from the matrix. The findings provide a study basis for identifying the potentially dangerous areas and provide early warning for the safety of underground engineering construction operations.

This study reports the effects of transition metal ions on the colour of blue-green beryl. Industrial cameras were used to measure colour in the CIELAB colour space. X-ray fluorescence (XRF), X-ray diffraction (XRD), infrared spectroscopy (IR), and ultraviolet-visible (UV–vis) spectroscopy were used for characterization. The d–d transition of Fe3+ with sixfold coordination, the O2−→Fe3+ charge transfer, and the charge transition of binuclear metal M–M complexes formed by [Fe2(OH)4]2+ in the channel caused a yellow tone, whereas the charge transfer of Fe2+/Fe3+ with sixfold coordination caused a blue-green tone. The chroma of blue-green beryl was negatively correlated with the ratio of Cs+Mn to Fe contents. The lightness of blue-green beryl was negatively correlated with the total content of transition metal ions.

The bed pressure drop, minimum fluidized gas velocity, bed density, and bed expansion rate are important parameters characterizing the fluidization characteristics of gas-solid fluidized beds. By analyzing these parameters, the advantages and disadvantages of the fluidization state can be known. In this study, experiments were conducted to study the fluidization characteristics of a gas-solid magnetically fluidized bed for microfine particles by changing the magnetic field strength, magnetic field addition sequence, and static bed height. The experimental results show that when the magnetic field strength increased from 0 KA/m to 5 KA/m, the minimum fluidized gas velocity of particles increased from 4.42 cm/s to 10.32 cm/s, while the bed pressure drop first increased and then decreased. When the magnetic field strength is less than 3.4 KA/m, the microfine particles in the bed are mainly acted on by the airflow; while when the magnetic field strength is greater than 3.4 KA/m, the microfine particles are mainly dominated by the magnetic field. The magnetic field addition sequence affects the fluidization quality of microfine particles. The fluidized bed with ‘adding magnetic field first’ shows a more stable fluidization state than ‘adding magnetic field later’. Increasing of the static bed height reduces the bed expansion rate. The bed expansion rate is up to 112.5% at a static bed height of h0 = 40 mm and H = 5 KA/m. This will broaden the range of density regulation of a single magnetic particle and lay the advantage of gas-solid magnetically fluidized bed for microfine particles in the field of separation of fine coal.

Recycling of tailings in the form of cemented paste backfill (CPB) is a widely adopted practice in the mining industry. Environmental performance is an important design criterion of CPB structures. This environmental performance of CPB is strongly influenced by its saturated hydraulic conductivity (permeability). Superplasticizers are usually added to improve flowability, but there is a limited understanding of their influence on the hydraulic properties of the CPB. This paper presents new experimental results on the variations of the hydraulic conductivity of CPB containing polycarboxylate-based superplasticizer with different compositions and curing conditions. It is found that the hydraulic conductivity of the CPB decreases with the addition of superplasticizer, which is beneficial to its environmental performance. The reduction is largely attributable to the influence of the ether-based superplasticizer on particles mobility and cement hydration. Moreover, both curing temperature and time have correlations with the hydraulic conductivity of CPB containing superplasticizer. In addition, the presence of sulfate and partial replacement of PCI with blast furnace slag reduces the hydraulic conductivity. The variations are mainly due to the changes in the pore structure of the CPB. The new results discussed in this manuscript will contribute to the design of more environmental-friendly CPBs, which is essential for sustainable mining.

As the main part of the Indosinian metallogenic province in the eastern part of the Tethys metallogenic domain, Southeast Asia has experienced multiple stages of tectonic magnetic activities accompanied by the formation of rich mineral resources. However, due to the undeveloped economy, low degree of geological work, dense vegetation cover, and lack of obvious prospecting marks, traditional geological prospecting work in the area is not optimal. Consequently, the combination of high-precision geophysics and geochemistry has become an important method of looking for ore bodies deep underground in this area. The Nanpo gold deposit is a hydrothermal gold deposit that occurs in the Indosinian felsic volcanic rock body, and its mineralization is closely related to felsic magmatism. This study carried out comprehensive geophysical and geochemical exploration methods of soil geochemical survey, induced polarization (IP) survey, and audio-frequency magnetotelluric (AMT) survey. Based on the characteristics of geophysical and geochemical anomalies, geological inference, and interpretation, the integrated geophysical and geochemical prospecting criteria of the ore area have been determined: The large-scale and overlapping Au-Ag-Cu anomaly area in the host felsic magmatic rocks (mainly diorite, monzodiorite and granodiorite) is a favorable metallogenic area. Two anomalies, P1–H1 and P3–H6, with the best metallogenetic conditions and the deepest extensions of the known ore bodies, were further selected as engineering verification targets. After the study of the drill core, gold (mineralized) bodies consistent with the anomalies were found, indicating that the combined method is suitable for the exploration of mineral resources in this area, and the prospecting effect is good. At the same time, the metallogenic prediction shows that the deep part of the mining area still has great metallogenic prospects and prospecting potential. The characteristics of geophysical and geochemical anomalies and prospecting experience in the study area can provide references for the prospecting of hydrothermal gold deposits in the Luang Prabang–Loei structural belt.

The number of parallel joints has an impact on the size effect of the uniaxial compressive strength and characteristic strength of a rock; however, the relationships between them are yet to be derived. We studied the influence of the number of joints and rock size on the uniaxial compressive strength of the rock. This study established ten numerical simulation programs using numerical simulations and the RFPA software. Stress–strain curves of different numbers of parallel joints and sizes of rocks were analyzed. Relationships between the uniaxial compressive strength and number of parallel joints and rock size were proposed, and their special functions were obtained. Mathematical models between rock characteristic size, rock characteristic strength and the number of parallel joints were established. Simulations of the verification program confirmed that these relationships are still applicable after the angle of parallel joints changes.

The Yuqia uranium deposit is a newly discovered sandstone-type uranium deposit in the northern margin of the Qaidam Basin. Concerning the sources of sediment in the basin, most scholars have focused on the study of Cenozoic sediment sources in the northern part of the basin, rather than on the study of Jurassic provenance and its implications for uranium mineralization. In this paper, the Jurassic sandstones in the area were selected for petrography, petrogeochemistry and electron microprobe analysis (EPMA), and the significance of sedimentary provenance and uranium metallogeny were further discussed, based on the previous data of detrital zircon chronology. It is reported here for the first time that coffinite and pitchblende are the main contributors. Independent uranium minerals in the region mainly occur in strawberry pyrite, xenotime, and margins or of quartz. The rocks in the source area, Jurassic sandstones, were mainly formed under the tectonic setting of the active continental margin; however, the sediments are mainly derived from the Indosinian and Paleozoic granitoids exposed in the northern margin of the Qaidam Basin. The uranium-rich granites in the source area led to the preconcentration of uranium in the sandstone of the target layer, and the uranium was brought into the ore-bearing target layer through uranium-bearing oxygenated water. The reduction reaction occurred under the action of reducing matter, and finally, the U6+ was reduced to U4+ in the formation of coffinite and pitchblende.

Underground coal mining of CH4 gas-rich tectonic coal seams often induces methane outburst disasters. Investigating gas permeability evolution in pores of the tectonic coal is vital to understanding the mechanism of gas outburst disasters. In this study, the triaxial loading–unloading stresses induced gas permeability evolutions in the briquette tectonic coal samples, which were studied by employing the triaxial-loading–gas-seepage test system. Specifically, effects of loading paths and initial gas pressures on the gas permeability of coal samples were analyzed. The results showed the following: (1) The gas permeability evolution of coal samples was correlated with the volumetric strain change during triaxial compression scenarios. In the initial compaction and elastic deformation stages, pores and cracks in the coal were compacted, resulting in a reduction in gas permeability in the coal body. However, after the yield stage, the gas permeability could be enhanced due to sample failure. (2) The gas permeability of the tectonic coal decreased as a negative exponential function with the increase in initial gas pressure, in which the permeability was decreased by 67.32% as the initial gas pressure increased from 0.3 MPa to 1.5 MPa. (3) Coal samples underwent a period of strain development before they began to fail during confining pressure releasing. After the stress releasing-induced yield stage, the coal sample was deformed and cracked, resulting in a quickly increase in gas permeability. With a further releasing process, failure of the sample occurred, and thus induced rapidly increasing gas permeability. These obtained results could provide foundations for gas outburst prevention in mining gas-rich tectonic coal seams.

Airflow classification is the key technology for the dry separation of manufactured sand. To solve the problem of low separation accuracy and poor gradation grade, the classification process of manufactured sand under different inlet and outlet airflow velocities changes in the multi-air inlet classifier is simulated by using Barracuda based on Computational Particle Fluid Dynamics (CPFD) method. The influence of various airflow velocity in air inlets and outlet on the sand classification is analyzed. The optimal combination of airflow velocity that meets the design goals is obtained. The results show that the airflow velocity and location of the air inlet and outlet have a significant impact on medium-grained (0.15~1.18 mm) and fine-grained (0.075~0.3 mm) sand. Adjusting the airflow velocity at air inlet 2 and air outlet can most effectively change the overall sand separation effect, while 41 m/s (inlet 2) and 6 m/s (outlet) would be the best velocity combination.

The paper concerns investigation of the effect of impact crusher operation on selected qualitative characteristics of mineral aggregate products. Qualitative characteristics of crushing products in terms of size reduction ratio and fine particles contents were analyzed from the point of view of operational parameters of the impact crusher. An investigative program was carried out on a plant scale and two primary parameters of the impactor were analyzed: velocity of the crusher rotor and the width of the outlet gap. The models of the crushing device operation were built separately for each type of the tested material, as well as for general conditions.

Significant volumes of rhyolites and granites of the Pliocene-Pleistocene age are exposed in the collision zone of the Greater Caucasus, Russia. The volcanic history of the region includes ignimbrites and lavas associated with the Chegem caldera (2.9 Ma) and Elbrus volcano (1.98 and 0.7 Ma) and rhyolitic necks and granites in Tyrnyauz (1.98 Ma). They are characterized by a similar bulk and mineral composition and close ratios of incompatible elements, which indicates their related origin. The 1.98 Ma Elbrus ignimbrites, compared to the 2.9 Ma Chegem ignimbrites, have elevated concentrations of both compatible (Cr, Sr, Ca, Ni) and incompatible elements (Cs, Rb, U). We argue that the Elbrus ignimbrites were produced from magma geochemically similar to Chegem rhyolites through fractionation crystallization coupled with the assimilation of crustal material. The 1.98 Ma Eldjuta granites of Tyrnyauz and early ignimbrites of the Elbrus region (1.98 Ma) are temporally coeval, similar mineralogically, and have comparable major and trace element composition, which indicates that the Elbrus ignimbrites probably erupted from the area of modern Tyrnyauz; the Eldjurta granite could represent a plutonic reservoir that fed this eruption. Late ignimbrites of Elbrus (0.7 Ma) and subsequent lavas demonstrate progressively more mafic mineral assemblage and bulk rock composition in comparison with rhyolites. This indicates their origin in response to the mixing of rhyolites with magmas of a more basic composition at the late stage of magma system development. The composition of these basic magmas may be close to the basaltic trachyandesite, the flows exposed along the periphery of the Elbrus volcano. All studied young volcanic rocks of the Greater Caucasus are characterized by depletion in HSFE and enrichment in LILE, Li, and Pb, which emphasizes the close relationship of young silicic magmatism with magmas of suprasubduction geochemical affinity. An important geochemical feature is the enrichment of U up to 8 ppm and Th up to 35 ppm. The trace element composition of the rocks indicates that the original rhyolitic magma of Chegem ignimbrites caldera was formed at >80%–90% fractionation of calc-alkaline arc basalts with increased alkalinity. This observation, in addition to published data for isotopic composition (O-Hf-Sr) of the same units, shows that the crustal isotopic signatures of silicic volcanics may arise due to the subduction-induced fertilization of peridotites producing parental basaltic magmas before a delamination episode reactivated the melting of the former mantle and the lower crust.

The Oeyama ophiolite unit is one of the oldest components of the subduction orogenic belts in the Japanese Islands and is important for understanding the initiation of plate subduction in the proto-Japan region. This study performed U–Pb and Lu–Hf isotopic and trace element analyses of zircon in gabbroic rocks from the Oeyama mafic–ultramafic complex, the type locality of the Oeyama ophiolite unit. This study obtained a weighted average zircon 206Pb/238U age of 544 ± 4 Ma, which indicates an igneous age of the gabbroic rock. Trace element analysis of the zircons revealed that the host rock was derived from the mantle depleted of incompatible elements such as the depleted mid-oceanic ridge mantle. The present igneous age and geochemical features of the zircons are consistent with previous work for other parts of the Oeyama ophiolitic unit. The isotopic signature of Hf also indicated that the gabbroic rock was derived from the depleted mantle domain. The Hf isotopic signature is more depleted than those represented by zircons in the jadeitite associated with the Oeyama ophiolite unit. These results demonstrated that the older crustal material was involved in the initial oceanic plate subduction along the proto-Japan arc.

The enhanced cementation technique by galvanic interaction of aluminum (Al; electron donor) and activated carbon (AC; electron mediator) to recover gold (Au) ions from the ammonium thiosulfate solution is a promising technique to eliminate the challenges of poor recovery in the system. This study presents the kinetics of Au ion cementation in an ammonium thiosulfate lixiviant as functions of initial Au concentration, size/amount of Al and AC, temperature, and shaking speed. The recovery results basically followed first order kinetics and showed that the cementation rate increased with a higher initial concentration of Au, smaller electron donor size, greater both electron donor and mediator quantity, decrease in temperature, and higher shaking speed in the system, while size of electron mediator did not significantly affect Au recovery.

Several pottery sherds from the Svilengrad-Brantiite site, Bulgaria, were mineralogically and petrographically analyzed. The aim was to add information to the very scarce material data available for Early Bronze Age pottery in the southeastern Thrace plain, Bulgaria, in order to examine a possible raw-material source of the pottery. The characterization techniques applied were optical microscopy (OM), petrographic microscopy (PM), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray fluorescence (XRF) spectroscopy, and X-ray diffraction (XRD). The pottery samples consisted of two typological groups: a local-made type and a cord-impressed decoration type influenced by foreign cultures. All of the samples were produced from fine clay pastes that had a quite similar composition, with abundant mineral grains of similar mineral composition and fragments of metamorphic and granitic rocks. The chemical compositions of each mineral in the grains and fragments were almost identical, and consistent with those from metamorphic and granitic rocks from the Sakar-Strandja Mountains near the study site. The clay paste compositions corresponded to those of illite/smectite mixed-layer clay minerals or mixtures of illite and smectite, and the clay-mineral species were consistent with those in Miocene–Pleistocene or Holocene sediments surrounding the site.

This study reported the detrital zircon U-Pb geochronology of the Cenozoic sequence exposed in Kotli, northwestern Himalaya, Pakistan, which forms part of the Kashmir foreland basin. The U-Pb detrital age patterns of the Paleocene Patala Formation show a major age cluster between ~130–290 Ma, ~500–1000 Ma and ~1000–1500 Ma, which mainly resembles the lesser and higher Himalayan sequence. However, the younger age pattern (~130–290 Ma) can be matched to the ages of the ophiolites exposed along the Indus–Tsangpo suture zone. In addition, two younger grains with 57 Ma and 55 Ma ages may indicate a contribution from the Kohistan-Ladakh arc. The detrital zircons in the upper Tertiary sequence show the increased input of younger detrital ages

Iron silicide minerals (Fe-Si group) are found in terrestrial and solar system samples. These minerals tend to be more common in extraterrestrial rocks such as meteorites, and their existence in terrestrial rocks is limited due to a requirement of extremely reducing conditions to promote their formation. Such extremely reducing conditions can be found in fulgurites, which are glasses formed as cloud-to-ground lightning heats and fuses sand, soil, or rock. The objective of this paper is to review reports of iron silicides in fulgurites, note any similarities between separate fulgurite observations, and to explain the core connection between geological environments wherein these minerals are found. In addition, we also compare iron silicides in fulgurites to those in extraterrestrial samples.

A novel approach for Ta and Nb extraction consisting of the pre-treatment of a coltan-bearing ore with an ammonium bifluoride sub-molten salt and subsequent acid leaching has been studied. The effects from ore granulometry, ammonium bifluoride (ABF) to ore mass ratio, temperature and duration of fluorination on the degree of Ta and Nb extraction were examined. The ABF to ore ratio and process temperature were found to have the most pronounced impact on extraction efficiency. The following optimal process conditions were determined: ore granulometric fraction (−75 + 45 µm), ABF-ore (5/1), fluorination temperature (200 °C) and fluorination time (2.5 h). Maintaining these parameters enabled about 94% of Ta and 95% of Nb to be brought into solution during the sulfuric-acid-leaching stage. A comparison of the proposed method with previously reported studies suggests that due to the effects of mechanical agitation and the recirculation of the HF-containing gaseous phase back into the process, the dosage rate of ABF at the fluorination stage could be reduced significantly without sacrificing the overall recovery of Ta and Nb. In such a way, the approach could offer added environmental benefits since release of fluoride-containing effluents into the environment could be limited.

The use of untreated recycled water has negative effects in the flotation of zinc sulfide ores due to the presence of dissolved species, such as magnesium and calcium. Although it has been found that magnesium is a more potent depressant than calcium, it has not been investigated in this role or for the effect of adding sodium carbonate. The results of an investigation to evaluate the effect of magnesium on the hydrophobicity of Cu-activated sphalerite conditioned with Sodium Isopropyl Xanthate (SIPX) are presented. Zeta potential of natural and Cu-activated sphalerite as a function of the conditioning pH and Cu(II) concentration, respectively, was first evaluated. Later, the effect of pH and presence of magnesium on the contact angle of Cu-activated sphalerite conditioned with SIPX was studied; it was also evaluated the effect of sodium carbonate to counteract the effect of magnesium. Cu-activation enhances the zeta potential of sphalerite up to a concentration of 5 mg/L. Contact angle tests, thermodynamic simulation, and surface analysis showed that magnesium hydroxide precipitates on the sphalerite surface at pH 9.6, decreasing its hydrophobicity. Addition of sodium carbonate as alkalinizing agent precipitates the magnesium in the form of a species that remained dispersed in the bulk solution, favoring the contact angle of Cu-activated sphalerite and, consequently, its hydrophobicity. It is concluded that the use of sodium carbonate as alkalinizing agent favors the precipitation of magnesium as hydromagnesite (Mg5(OH)2(CO3)4∙4H2O) instead of hydroxide allowing the recovery of sphalerite.

In recent years, mineral resources near the surface are becoming scarce, causing focused mineral exploration on concealed deposits in covered terrains. In northern China, covered terrains are widespread and conceal bedrock sequences and mineralization. These represent geochemical challenges for mineral exploration in China. As a deep-penetrating geochemical technology that can reflect the information of deep anomalies, the fine-grained soil prospecting method has achieved ideal test results in arid Gobi Desert covered terrain, semi-arid grassland covered terrain, and alluvium soil covered terrain of northern China. The anomaly range indicated by the fine-grained soil prospecting method is very good with the known ore body location. The corresponding relationship can effectively indicate deep ore bodies and delineate anomalies in unknown areas. Overall, the fine-grained soil prospecting method can be applied to geochemical prospecting and exploration in covered terrains.

Three samples of meta-acidic rocks with pre-Alpine metamorphic relicts from the Sesia-Lanzo Zone eclogitic continental crust were investigated using stepwise controlled elemental maps by means of the Quantitative X-ray Maps Analyzer (Q-XRMA). Samples were chosen with the aim of analysing the reacting zones along the boundaries between the pre-Alpine and Alpine mineral phases, which developed in low chemically reactive systems. The quantitative data treatment of the X-ray images was based on a former multivariate statistical analytical stage followed by a sequential phase and sub-phase classification and permitted to isolate and to quantitatively investigate the local paragenetic equilibria. The parageneses thus observed were interpreted as related to the pre-Alpine metamorphic or magmatic stages as well as to local Alpine re-equilibrations. On the basis of electron microprobe analysis, specific compositional ranges were defined in micro-domains of the relict and new paragenetic equilibria. In this way calibrated compositional maps were obtained and used to contour different types of reacting boundaries between adjacent solid solution phases. The pre-Alpine and Alpine mineral parageneses thus obtained allowed to perform geothermobarometry on a statistically meaningful and reliable dataset. In general, metamorphic temperatures cluster at 600–700 °C and 450–550 °C, with lower temperatures referred to a retrograde metamorphic re-equilibration. In all the cases described, pre-Alpine parageneses were overprinted by an Alpine metamorphic mineral assemblage. Pressure-temperature estimates of the Alpine stage averagely range between 420 to 550 °C and 12 to 16.5 kbar. The PT constraints permitted to better define the pre-Alpine metamorphic scenario of the western Austroalpine sectors, as well as to better understand the influence of the pre-Alpine metamorphic inheritance on the forthcoming Alpine tectonic evolution.

Ferromanganese nodules have been recognized as a potential future metal source for over 50 years. Many research and development efforts have been conducted by many organizations. Most of the efforts have been concentrated into the mining technologies especially for hydraulic lifting through riser pipes with bulk-scale nodule collector. However, no commercial mining venture exists. Uncertainty in the economy of nodule mining is considered to be the reason for this. In order to improve the economy, a mining subsystem based on mechanical lifting and small-scale collectors is proposed and the preliminary economic feasibility is examined in this study. The benefit was at a favorable level compared with that using hydraulic lifting with bulk-scale collector. From the viewpoint of environmental impact assessment, environmental considerations of deep-sea sediment plume are explained.

Sodium metabisulfite (MBS) was used in this study for selective flotation of chalcopyrite and molybdenite. Microflotation tests of single and mixed minerals were performed to assess the floatability of chalcopyrite and molybdenite. The results of microflotation of single minerals showed that MBS treatment significantly depressed the floatability of chalcopyrite and slightly reduced the floatability of molybdenite. The results of microflotation of mixed minerals demonstrated that the MBS treatment could be used as a selective chalcopyrite depressant in the selective flotation of chalcopyrite and molybdenite. Furthermore, the addition of diesel oil or kerosene could significantly improve the separation efficiency of selective flotation of chalcopyrite and molybdenite using MBS treatment. A mechanism based on X-ray photoelectron spectroscopy analysis results is proposed in this study to explain the selective depressing effect of MBS on the flotation of chalcopyrite and molybdenite.

In this study, we carried out the analysis of the impact melt vein glasses from the Kara impact crater (Russia) in comparison to low-pressure impact melt glasses (tektites) of the Zhamanshin crater (Kazakhstan). 27Al, 23Na, and 29Si MAS NMR spectra of the samples of these glasses were analyzed. The samples of the natural glass contained inclusions of crystalline phases, paramagnetic elements that greatly complicate and distort the NMR signals from the glass phase itself. Taking into account the Mossbauer distribution of Fe in these glasses, the analysis of the spectra of MAS NMR of glass network-former (Si, Al) and potential network-modifiers (Na) of nuclei leads to the conclusion that the Kara impact melt vein glasses are characterized by complete polymerization of (Si,Al)O4 tetrahedral structural units. The NMR features of the glasses are consistent with the vein hypothesis of their formation under conditions of high pressures and temperatures resulting in their fluidity, relatively slow solidification with partial melt differentiation, polymerization, and precipitation of mineral phases as the impact melt cools. The 70 Ma stability of the Kara impact vein glass can be explained by the stabilization of the glass network with primary fine-dispersed pyroxene and coesite precipitates and by the high polymerization level of the impact glass.