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Minerals, Volume 12, Issue 5 (May 2022) – 163 articles

Cover Story (view full-size image): Magnetite (Fe2+Fe3+2O4) crystal cells contain Fe atoms in tetrahedral and octahedral sites and crystallize in the spinel structure with a face-centered cubic cell. Under geological conditions, the structure is modified by natural defects formed during crystallization, and those produced during the alpha decay of U, Th, and Sm isotopes present naturally. The produced radiogenic 4He atoms are incorporated into different atomic interstitial sites and defect sites and diffuse by hopping between those sites depending on the temperature. To quantify the natural and radiation defect on He diffusion, a theoretical investigation of energy mapping along the diffusion paths has been conducted using the energy density functional theory, which allows calculating the migration energy as shown in the figure. View this paper
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Article
Geochemistry of Mudstones/Silty Mudstones from the Qigequan Formation and Shizigou Formation in Yuejin-II Area, Southwestern Area of the Qaidam Basin: Implications for Sedimentary Environment and Sandstone-Type Uranium Mineralization
Minerals 2022, 12(5), 658; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050658 - 23 May 2022
Viewed by 475
Abstract
The Qaidam Basin has been the focus of sandstone-type uranium prospecting since the 1950s. In recent years, relying on the uranium geological survey project supported by the China Geological Survey, and the cooperation with the Qinhai oil company, drilling work at the Yuejin-II [...] Read more.
The Qaidam Basin has been the focus of sandstone-type uranium prospecting since the 1950s. In recent years, relying on the uranium geological survey project supported by the China Geological Survey, and the cooperation with the Qinhai oil company, drilling work at the Yuejin-II area in this basin has achieved breakthroughs on industrial-level sandstone-type uranium exploration. In this study, we present major, trace and REE geochemical analysis of the Qigequan Formation and the Shizigou Formation mudstones/silty mudstones collected from an industrial uranium ore drillholes in the Yuejin-II area. The Shizigou and Qigequan Formations exhibit signatures of non-intense alteration, low rock maturity and proximal provenance. The overall arid paleoclimatic conditions controlled the sedimentation of large volume of uranium rich materials. The period of relative humidity prompted the sedimentation of reduced agents. Aided by the neotectonic-induced slopes and tectonic windows, oxygenated fluids migrated along permeable layers and extracted the hexavalent uranium, transported in the form of uranyl ion (UO22+). When the oxygen–uranium-rich fluids finally infiltrated into the reductive sand body, the hexavalent uranium was reduced to tetravalent uranium and deposited in the form of uranium compounds. Large-scale and centrally distributed reductive sand bodies provided favorable ore storage space for the sandstone-type uranium mineralization in the Yuejin-II area. Full article
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Article
Petrochronological Evidence for a Three-Stage Magmatic Evolution of the Youngest Nepheline Syenites from the Ditrău Alkaline Massif, Romania
Minerals 2022, 12(5), 657; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050657 - 23 May 2022
Viewed by 423
Abstract
The Ditrău Alkaline Massif (DAM) is an igneous massif in the Eastern Carpathian Mountains of Romania. Numerous geochronological and geochemical studies have proposed a long formation history (ca. 70 m.y.) of the DAM from Middle Triassic to Cretaceous times, which is hardly reconcilable [...] Read more.
The Ditrău Alkaline Massif (DAM) is an igneous massif in the Eastern Carpathian Mountains of Romania. Numerous geochronological and geochemical studies have proposed a long formation history (ca. 70 m.y.) of the DAM from Middle Triassic to Cretaceous times, which is hardly reconcilable with geochemical evolutionary models and the geotectonic environment during the Mesozoic in this part of the Eastern Carpathian Mountains. In order to put tighter age constraints on the igneous processes forming the DAM, two nepheline syenites from the so-called Ghiduţ and Lăzarea suites were investigated. Based on field and geochemical evidence, the two rock suites represent the younger part of the DAM intrusives. Detailed zircon characterization, in situ zircon SIMS U-Pb dating, and geochemical modelling were used to establish the timing of zircon crystallization and thus to set time constraints on the igneous formation of these parts of the DAM. The intrusion of the dated Ghiduţ suite sample took place at 232 ± 1 Ma in the Karnium, whereas the Lăzarea suite nepheline syenite sample was intruded at 225 ± 1 Ma in the Norium. Together with published geochemical and geochronological data, three different magmatic events can thus be identified: Ghiduţ suite at 231.1 ± 0.8 Ma, Ditrău suite at 230.7 ± 0.2 Ma, and Lăzarea suite at 224.9 ± 1.1 Ma. Although the ages of the events 1 and 2 are statistically indistinguishable, the combination of geochemical and petrochronological data certainly favor independent intrusion events. Thus, the igneous events forming the younger parts of the DAM encompassed a time span of ca. 13 m.y. Additionally, each igneous event can tentatively be divided in an older syenitic stage and a younger nepheline syenitic one, each with an age difference of some 100,000 years. No indication of any post 215 Ma igneous or hydrothermal activity was found. The new data and interpretation significantly improve our understanding of the temporal and geochemical evolution of the DAM and of alkaline complexes as such, demonstrating that the underlying igneous processes (melt generation, assimilation, fractionation, and the duration of plumbing systems) work on the same time scale for both sorts of magmatic rock suites. Full article
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Article
Zircon U-Pb-Hf Isotopes, Biotite 40Ar/39Ar Geochronology, and Whole-Rock Geochemistry of the Baogeqi Gabbro in the Northern Alxa, Southernmost Central Asian Orogenic Belt
Minerals 2022, 12(5), 656; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050656 - 23 May 2022
Viewed by 408
Abstract
The final closure time of the Paleo-Asian Ocean and the Permo-Carboniferous tectonic settings in the northern Alxa are very important but controversial tectonic issues. The geochronology and petrogenesis of mafic igneous rocks are superior in clarifying regional tectonic settings. Here, we report on [...] Read more.
The final closure time of the Paleo-Asian Ocean and the Permo-Carboniferous tectonic settings in the northern Alxa are very important but controversial tectonic issues. The geochronology and petrogenesis of mafic igneous rocks are superior in clarifying regional tectonic settings. Here, we report on zircon U-Pb-Hf isotopes, biotite 40Ar/39Ar geochronology and whole-rock geochemical data of the hornblende gabbro from the Baogeqi gabbro pluton in the northern Alxa. The LA-ICP MS U-Pb analysis of zircon grains from the hornblende gabbro yield a weighted mean age of 262.7 ± 2.3 Ma (2σ, MSWD = 0.74), manifesting that the Baogeqi gabbro pluton emplacement was during the late Middle Permian (Capitanian). The 40Ar/39Ar dating of biotite grains from the hornblende gabbro yields a plateau age of 231.3 ± 1.6 Ma (2σ, MSWD = 0.55), indicating that the Baogeqi gabbro pluton cooled to below 300 ℃ in the Triassic. The hornblende gabbro samples are calc-alkaline with metaluminous character, and show enrichment in large ion lithophile elements (e.g., Rb, Ba, Sr, and K) but depletion in Nb, Ta, P, Th, and Ti relative to primitive mantle. Combined with the positive zircon εHf(t) values (+4.9–+9.4), we suggest that the magmas formed from the partial melting of depleted mantle were metasomatized by slab-derived fluids. Together with regional geology, these geochemical data suggest that the Baogeqi gabbro pluton was formed in an intracontinental extension setting, further indicating that the Paleo-Asian Ocean in the northern Alxa was closed prior to the late Middle Permian (Capitanian), and this region was in a post-collision extensional setting during the Capitanian-Late Permian. In addition, the Triassic cooling of the gabbro pluton may be a record of the decline of the Capitanian-Late Permian post-collisional extension basin due to the far-field effect of subduction-collision during the closure of the Paleo-Tethys Ocean. Full article
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Article
Potential Use of Municipal Waste Incineration Ash as a Hardening Slurry Ingredient
Minerals 2022, 12(5), 655; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050655 - 23 May 2022
Viewed by 408
Abstract
In recent years, there has been a marked increase in the amount of municipal waste generated in Poland. In the context of circular economy assumptions, the key is the availability of technologies that would make it possible to safely process and reuse waste, [...] Read more.
In recent years, there has been a marked increase in the amount of municipal waste generated in Poland. In the context of circular economy assumptions, the key is the availability of technologies that would make it possible to safely process and reuse waste, especially when it is difficult to manage. One such direction is thermal waste treatment. In 2020, 21.6% of all municipal waste was subjected to this process. Consequently, the amount of ash generated is significant (approximately 2,823,000 tons annually). One of the uses of waste materials is the sealing of earth hydrotechnical facilities, such as flood embankments, water dams, and embankments of waste landfills. For this purpose, cut-off screens made of hardening slurries are used. In order to improve the tightness and corrosion resistance of hardening suspensions, combustion by-products are added to their composition. The article presents an assessment of the possibility of using ashes from municipal waste incineration as an additive to hardening slurries. It also discusses the technological and operational parameters of hardening slurries with the addition of the ashes in question. Binding requirements for hardening slurries used for the construction of cut-off walls is also defined. The experiment showed that the tested hardening slurries meet most of the suitability criteria. Further research directions are proposed to fully identify other properties of hardening slurries in terms of their environmental impact. Full article
(This article belongs to the Special Issue Fly Ashes: Characterization, Processing and Utilization)
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Article
Evolution Characteristics of Overlying Strata Fractures in Paste Composite Filling Stope
Minerals 2022, 12(5), 654; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050654 - 22 May 2022
Viewed by 418
Abstract
Paste composite filling mining (PCFM) is one of the effective ways to achieve water-preserved mining (preservation of the waterproof strata). To investigate the laws of fracture propagation of the overlying strata in the PCFM stope, a kinematic model of overlying strata in the [...] Read more.
Paste composite filling mining (PCFM) is one of the effective ways to achieve water-preserved mining (preservation of the waterproof strata). To investigate the laws of fracture propagation of the overlying strata in the PCFM stope, a kinematic model of overlying strata in the PCFM was established, which identified the major determinants to the development of overlying strata fractures. Taking the 112,201 working face of the test mine as the research background, the physical similar simulation, numerical computation, and theoretical analysis were combined to analyze the development characteristics of overlying strata fractures in the PCFM under the reaction between many factors (mining height, filling ratio, burial depth). The results show that the larger the mining height of the working face, the larger the development degree of overlying strata fractures. When the mining height is smaller, fractures are mostly distributed on both sides of the coal wall; when the mining height is larger, overlying strata fractures are mostly distributed on both sides of the coal wall and the upper part of overlying strata. The larger the paste filling ratio of the working face, the smaller the development degree of overlying strata fractures. Overlying strata fractures are mostly distributed in overlying strata on both sides of the coal wall. When the filling ratio of the working face increases, it is possible to effectively control the development of overlying strata fractures. The shallower the burial depth of the working face is, the faster the fractures are developed. With the increase of the burial depth, the development of overlying strata fractures is reduced, and overlying strata fractures will finally tend to be a stable value. The research results provide an important theoretical foundation for the application of the localized paste filling mining technique in the water-preserved mining, and also complement the theories of filling mining. Full article
(This article belongs to the Special Issue Backfilling Materials for Underground Mining, Volume III)
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Article
Geophysical Implications for Prospective Prediction of Copper Polymetallic Ore Bodies: Northern Margin of Alxa Block, China
Minerals 2022, 12(5), 653; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050653 - 22 May 2022
Viewed by 447
Abstract
The Alxa Block is located in the middle part of the Central Asian orogenic belt, which is the coupling belt of the North China, Tarim, and Kazakhstan Plates. The east–west-trending deep faults control stratigraphic distribution and magmatic activity in the region. To detect [...] Read more.
The Alxa Block is located in the middle part of the Central Asian orogenic belt, which is the coupling belt of the North China, Tarim, and Kazakhstan Plates. The east–west-trending deep faults control stratigraphic distribution and magmatic activity in the region. To detect the EW-trending ore-controlling deep structures, a 440 km NS section of magnetotelluric sounding was conducted from Minle to Ejinaqi. The phase tensor and electrical principal axis were analyzed based on the measured data to build the exploration model. The electrical structure model along the section was obtained using nonlinear conjugate gradient (NLCG) 2D inversion. Combined with the geological, geophysical, and deposit distribution characteristics in the area, the comprehensive study of magnetotelluric sounding profile shows that the resistivity presents as zoned along the profile. The Engelwusu ophiolite mélange belt is stacked in clumps with high and low resistivity, indicating that the northern margin of the Engelwusu Belt subducts below the high-resistivity zone, representing the passive continental margin. The southern end of the Engelwusu ophiolite belt is primarily the prospecting potential area for copper–gold deposits, whereas the northern end of the Engelwusu ophiolite belt corresponds to copper polymetallic deposits. Full article
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Article
Geological Significance of Late Permian Magmatic Rocks in the Middle Section of the Ailaoshan Orogenic Belt, SW China: Constraints from Petrology, Geochemistry and Geochronology
Minerals 2022, 12(5), 652; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050652 - 21 May 2022
Viewed by 396
Abstract
The Ailaoshan orogenic belt, located in the SE margin of the Qinghai–Tibet Plateau, is an important Paleo-Tethys suture zone in the eastern margin of the Sanjiang Tethys tectonic domain. The areas of Mojiang and Zhenyuan, located in the middle part of the Ailaoshan [...] Read more.
The Ailaoshan orogenic belt, located in the SE margin of the Qinghai–Tibet Plateau, is an important Paleo-Tethys suture zone in the eastern margin of the Sanjiang Tethys tectonic domain. The areas of Mojiang and Zhenyuan, located in the middle part of the Ailaoshan orogenic belt, are the key parts of the Ailaoshan Paleo-Tethys Ocean closure and collision orogeny. The rhyolites outcropped in the Mojiang area, and the granite porphyries outcropped in Zhenyuan area, are systematically studied for petrology, isotope geochemistry and geochronology. The Zircon U-Pb geochronology of rhyolites and granite porphyries give weighted average ages of 253.4 ± 4.2 Ma and 253.3 ± 2.0 Ma, respectively, both of which were formed in the late Permian period. The rhyolites belong to potassic calc-alkaline to subalkaline series. The patterns of the rare earth elements (REE) show a right-inclined seagull-type distribution, and the trace elements plot is right-inclined. The granite porphyries are high potassic calc-alkaline to subalkaline. The REE patterns show a right-inclined distribution, and the trace elements plot is right-inclined, which is consistent with the typical patterns observed in the crust. The peraluminous, highly differentiated and high ASI values suggest that rhyolites and granite porphyries are S-type granites. The zircon εHf(t) of the rhyolites range from −7.22 to −0.72, and two-stage Hf zircon model ages are (TDMC) 1771–2352 Ma, indicating that the magma source area is mainly crust-derived. The zircon εHf(t) of the granite porphyries range from −0.97 to 4.08, and two-stage Hf zircon model ages are (TDMC) 1336–1795 Ma, indicating that the magma is derived from a depleted mantle source and the partial melting of ancient crustal materials. The rhyolites and granite porphyries were possibly formed in the syn-collisional tectonic setting during the late Permian, and their ages limited the time of the final closure of the Ailaoshan Ocean and the initiation of collisional orogeny. Full article
(This article belongs to the Special Issue Petrology, Mineralogy, Geochemistry and Geochronology of Granites)
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Article
Boron Impurity Deposition on a Si(100) Surface in a SiHCl3-BCl3-H2 System for Electronic-Grade Polysilicon Production
Minerals 2022, 12(5), 651; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050651 - 21 May 2022
Viewed by 402
Abstract
A study of boron impurities deposited on a Si(100) surface in a SiHCl3-BCl3-H2 system is reported in this paper, using periodic density functional theory with generalized gradient approximation (GGA). The results show that the discrete distances of BCl [...] Read more.
A study of boron impurities deposited on a Si(100) surface in a SiHCl3-BCl3-H2 system is reported in this paper, using periodic density functional theory with generalized gradient approximation (GGA). The results show that the discrete distances of BCl3 and SiHCl3 from the surface of the Si(100) unit cell are 1.873 Å and 2.340 Å, respectively, and the separation energies are −35.2549 kcal/mol and −10.64 kcal/mol, respectively. BCl3 and SiHCl3 are mainly adsorbed on the surface of the Si(100) unit cell in particular molecular orientations: the positive position and the hydrogen bottom-two-front position from the analysis of the bond length change and adsorption energy. The adsorption of SiHCl3 and BCl3 is accompanied by a charge transfer from the molecule to the surface of the unit cell of 0.24 and 0.29 eV, respectively. BCl3 reacts more readily than SiHCl3 with the Si(100) surface, resulting in the deposition of boron impurities on the polysilicon surface. Full article
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Article
Peculiarities of Dynamics of Hypergenic Mineral Transformation of Nickel Weathering Crusts of Ultramafic Rocks of the Kempirsay Group of Deposits in Western Kazakhstan
Minerals 2022, 12(5), 650; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050650 - 20 May 2022
Viewed by 443
Abstract
Nickel weathering ores are used to produce metallic nickel, stainless steels, and nickel sulfate, the main component of batteries. The global production of nickel from weathering ores is increasing and has surpassed production from sulfide magmatic deposits. The efficiency of the mining and [...] Read more.
Nickel weathering ores are used to produce metallic nickel, stainless steels, and nickel sulfate, the main component of batteries. The global production of nickel from weathering ores is increasing and has surpassed production from sulfide magmatic deposits. The efficiency of the mining and processing of nickel ores from weathering rocks is determined by their mineralogical composition. The weathering crust profile of the Kempirsay ultramafite massif is divided into three zones—leached (kerolitized) serpentinites, nontronites, and final hydrolysis minerals (later referred to as “ochers”). The kerolitized zone consists of a mixture of Ni-bearing talc and saponites (later referred to as “kerolite”). During the geological mapping of the Donskoye, Buranovskoye, and Shelektinskoye deposits, the products of ultramafite hypergenic transformation into disintegrated and leached serpentinites, kerolites, nontronites, and ochers were selected and studied. For this purpose, 44 rock samples were studied via X-ray diffractometric and thermal analyses, supplemented with data from chemical, microscopic, and granulometric determinations. Based on the obtained numerical parameters of the crystalline structure of the weathering products, the thermochemical values were obtained. The hypergenic transformation of the initial minerals and their subsequent transformation were traced. The trace element distribution along the profile of the serpentinite weathering ores is related to the initial material composition of the ultramafites. The accumulation of nickel in industrial concentrations is associated with the nontronite–kerolite zone. X-ray diffractometric analysis can be used as a fast and reliable method for controlling the nickel content of ores and monitoring their mineralogical composition. Full article
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Article
Using Process Mineralogy as a Tool to Investigate Blending Potential of the Pentlandite-Bearing Ores at the Nkomati Ni Mine in South Africa
Minerals 2022, 12(5), 649; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050649 - 20 May 2022
Viewed by 417
Abstract
The mineralogy and texture of Ni-sulfide ores at the Nkomati nickel mine are highly variable, and this results in often erratic nickel recovery at the mine. The variability of the ore presents an opportunity to study the influence of grind size on the [...] Read more.
The mineralogy and texture of Ni-sulfide ores at the Nkomati nickel mine are highly variable, and this results in often erratic nickel recovery at the mine. The variability of the ore presents an opportunity to study the influence of grind size on the flotation-based recovery of Ni in highly heterogeneous sulfide ores, which would be applicable to this ore type at many other mines worldwide. In view of this, a process mineralogy investigation was conducted on thirteen mineralogically and texturally different nickel-sulfide ores from the Nkomati Nickel Mine, with a view on the influence of grind size on the flotation performance of pentlandite. Ore types presented include medium- and high-grade variants of the bleb, disseminated, massive, semi-massive, and net-textured sulfide ores of the Main Mineralized Zone (MMZ), as well as disseminated chromite-rich nickel sulfide ore and massive chromitite ore of the Peridotitic Chromitite Mineralized Zone (PCMZ). Laboratory scale metallurgical test work, comprising of sequential grinding and bench-top flotation testing of the ores, was conducted in combination with quantitative mineralogical investigation of the flotation feed and associated flotation products, using a FEI 600F Mineral Liberation Analyzer. The ore types under consideration require a variety of grind sizes (i.e., milling times) in order to attain optimal recovery of nickel through flotation. This is predominantly controlled by ore texture, and also partly by the abundance of the major constituent minerals in the ore, being pyroxenes, base metal sulfides, and chromite. Liberation of pentlandite is directly correlated with grind size (milling time), which is also positively correlated with the level of nickel recovery through flotation. A grind size of P80 at 75 µm results in the highest concentrate nickel grades of 7.5–8.1% in the PCMZ ores’ types which is the current grind for the PCMZ ores at Nkomati. A grind size of P77 at 75 µm yields the best overall pentlandite liberation, Ni recoveries of 84–88% and grades of 5.3–5.6% in the MMZ ores. This holds the potential to produce the best overall pentlandite liberation, nickel grades, recoveries from blending the MMZ and PCMZ ore types, and milling the composite ore at a target grind of P80 at 75 µm. Full article
(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation)
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Article
Microwave Dewatering of Gibbsite-Type Bauxite Ores: Permittivities, Heating Behavior and Strength Indices
Minerals 2022, 12(5), 648; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050648 - 20 May 2022
Viewed by 413
Abstract
Microwave radiation is a relatively new energy source that is being considered for several applications in mineral processing and extractive metallurgy. In the present research, various gibbsite-type bauxite ores were subjected to microwave radiation. The main objective was to assess the effect of [...] Read more.
Microwave radiation is a relatively new energy source that is being considered for several applications in mineral processing and extractive metallurgy. In the present research, various gibbsite-type bauxite ores were subjected to microwave radiation. The main objective was to assess the effect of microwave dewatering on the compressive strength indices of the ores and to compare the results obtained to those for conventional heating. Firstly, the fundamental interactions of the microwaves with the ores were evaluated by determining both the real and the imaginary permittivities as a function of temperature, and these were related to the water content. Secondly, the microwave heating behavior was modeled using a 24 factorial statistical analysis. Thirdly, the effect of dewatering by microwave heating on the compressive strength indices of roughly spherical bauxite ore pisoids was studied, and these results were compared to those obtained using conventional heating. Fourthly, the effect of particle size on the compressive strengths of irregular-shaped single particles of bauxite ore was investigated using both heating techniques. Finally, the energy requirements for dewatering of the ores, and hence reducing their compressive strengths, were compared for both processes. On the laboratory scale, the results showed that in comparison to conventional dewatering, microwave dewatering resulted in lower strength indices at both lower moisture removals and energy inputs. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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Article
Assessment of Materials and Rare Earth Metals Demand for Sustainable Wind Energy Growth in India
Minerals 2022, 12(5), 647; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050647 - 20 May 2022
Cited by 1 | Viewed by 582
Abstract
Wind energy is an alternative energy generation from non-renewable energy resources. The turbine is used to exploit wind energy. Different components of a wind turbine necessitate different materials and metals. There is a dependency of the materials on foreign countries. To avoid future [...] Read more.
Wind energy is an alternative energy generation from non-renewable energy resources. The turbine is used to exploit wind energy. Different components of a wind turbine necessitate different materials and metals. There is a dependency of the materials on foreign countries. To avoid future problems regarding the availability of these materials in India, it is necessary to forecast the quantity and the price of the materials and metals. Thus, this study mainly focuses on the estimation of the raw materials, rare earth, and critical metals used in manufacturing the wind turbine. Two wind turbines of 1.65 MW and 3.45 MW capacity, 78 m and 94 m hub height are considered for the study. The major raw materials are steel, aluminum, copper, cast iron, fiber glass with epoxy resin, and ceramic/glass. The requirement of rare earth elements (Nd) depends on the type of wind turbine direct drive or geared, and the type of generator used in the direct-drive wind turbine. The results estimated the requirement of materials and rare earth elements and the expected price in the future for 100% wind energy production in India. Full article
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Article
Mineral Paragenesis Precipitating in Salt Flat Pools of Continental Environments Replicated in Microbial Mat Microcosms without Evaporation
Minerals 2022, 12(5), 646; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050646 - 20 May 2022
Viewed by 420
Abstract
Mineral precipitation can be observed in natural environments, such as lagoons, rivers, springs, and soils. The primary precipitation process has long been believed to be abiotic due to evaporation, leading to phase supersaturation. However, biotic interactions of microbial metabolism, organic compounds, and dissolved [...] Read more.
Mineral precipitation can be observed in natural environments, such as lagoons, rivers, springs, and soils. The primary precipitation process has long been believed to be abiotic due to evaporation, leading to phase supersaturation. However, biotic interactions of microbial metabolism, organic compounds, and dissolved ions leading to mineral precipitation has been shown in laboratory studies using single-organism culture. The increase in pH inducing calcium carbonate precipitation due to oxygenic photosynthesis by Cyanobacteria and the release of ions due to organic matter decomposition by Firmicutes-inducing magnesium carbonate precipitation are recognized examples. As microbes do not live as pure cultures in natural environments but form complex communities, such pure culture lab studies do not reflect natural conditions. In this study, we grew natural complex microbial communities in microcosm conditions using filtered brine as water column and two types of natural gypsum substrates, and we replenished incubations to avoid evaporation. We monitored microbial communities through optical microscopy and analyzed mineral paragenesis in association with and without microbes, using different analytical techniques, such X-ray diffraction, and optical and field emission scanning electron microscopies. To detect changes throughout the experiment, small amounts of water column brine were extracted for physicochemial determinations. We were able to detect mineral paragenesis, avoiding evaporation, including major phases of chemical sedimentary rocks, such as gypsum, calcium carbonate, and some silicates in association to microbes. In addition, we evidenced that the use of natural substrates positively impacts growth of microbial communities, promoting the development of more biomass. This study can be seen as the first attempt and proof of concept of differentiating biotic and abiotic participation in evaporitic deposits, as they can form mineral paragenesis without evaporation. Future studies with microcosm experiments using microbial mats will be needed to establish mineral precipitation induced by micro-organisms and their extracellular polymeric substances (EPS), specifically to replicate mineral paragenesis sedimented from natural brines. Full article
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Review
The Gel Growth Technique—A Neglected Yet Effective Tool to Prepare Crystals of Oxysalts and Supergene Minerals
Minerals 2022, 12(5), 645; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050645 - 20 May 2022
Viewed by 350
Abstract
The technique of crystal growth in gels has nowadays become somewhat neglected in the scope of earth sciences, to the disadvantage of the experimental mineralogist. Even preparing an inorganic silica gel can prove a challenge to many, let alone successfully configure the entire [...] Read more.
The technique of crystal growth in gels has nowadays become somewhat neglected in the scope of earth sciences, to the disadvantage of the experimental mineralogist. Even preparing an inorganic silica gel can prove a challenge to many, let alone successfully configure the entire experiment. Based not only on previous literature but also on our extensive experience, crystals of many substances, including supergene minerals as reference standards, can be successfully grown in gel, aiding in accomplishing various research goals in earth sciences. Instead of providing the reader with an overwhelming compendium of historical information and theoretical knowledge of the subject which can be found elsewhere, we presented herein a comprehensive, practically oriented guide to the understanding and successful use of the technique of crystal growth in gels, mentioning, in addition to the general principle, the numerous pitfalls which we encountered during our own use of the method, and the ways to overcome them. Despite that the procedure is nowadays used mainly for the laboratory synthesis of organic or metal-organic compounds, we believe it to be a valuable asset to any mineralogist, and often, the only way to obtain inorganic reference material of a particular mineral of interest. Full article
(This article belongs to the Special Issue Mineral-Related Oxo-Salts: Synthesis and Structural Crystallography)
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Article
A Chemical Separation and Measuring Technique for Titanium Isotopes for Titanium Ores and Iron-Rich Minerals
Minerals 2022, 12(5), 644; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050644 - 20 May 2022
Viewed by 375
Abstract
Ti-isotope fractionation on the most Ti-rich minerals on Earth has not been reported. Therefore, we present a chemical preparation and separation technique for Ti-rich minerals for mineralogic, petrologic, and economic geologic studies. A two-stage ion-exchange column procedure modified from the previous literature is [...] Read more.
Ti-isotope fractionation on the most Ti-rich minerals on Earth has not been reported. Therefore, we present a chemical preparation and separation technique for Ti-rich minerals for mineralogic, petrologic, and economic geologic studies. A two-stage ion-exchange column procedure modified from the previous literature is used in the current study to separate Ti from Fe-rich samples, while α-TiO2 does not require chemical separation. Purified solutions in conjunction with solution standards were measured on two different instruments with dry plasma and medium-resolution mode providing mass-dependent results with the lowest errors. 49/47TiOL-Ti for the solution and solids analyzed here demonstrate a range of >5 far greater than the whole procedural 1 error of 0.10 for a synthetic compound and 0.07 for the mineral magnetite; thus, the procedure produces results is resolvable within the current range of measured Ti-isotope fractionation in these minerals. Full article
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Article
Temperature Variation Characteristics and Model Optimization of Flocculation Sedimentation of Overflow Ultra-Fine Iron Tailings
Minerals 2022, 12(5), 643; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050643 - 20 May 2022
Viewed by 286
Abstract
In order to study the effect of temperature on the settling characteristics of overflow ultra-fine iron tailings, the settling velocity of overflow ultra-fine iron tailings at eight different temperatures at 10–80 °C was experimentally studied. The results show that, with the increase in [...] Read more.
In order to study the effect of temperature on the settling characteristics of overflow ultra-fine iron tailings, the settling velocity of overflow ultra-fine iron tailings at eight different temperatures at 10–80 °C was experimentally studied. The results show that, with the increase in slurry temperature, the flocculation settling velocity of overflow ultra-fine iron tailings increases first and then decreases. That is, when the temperature is less than 60 °C, the settling velocity of flocs increases with the increase in temperature. When the temperature is 60 °C, the settling velocity reaches the maximum 5.66 mm/s. When the temperature is more than 60 °C, the settling velocity of tailings flocs gradually decreases. In addition, with the increase in the test temperature, when the temperature is less than 60 °C, the particle size, fractal dimension, and density of tailings flocculant gradually increase, the gap of flocculant structure gradually decreases, and the floc structure becomes denser. When the temperature is higher than 60 °C, the particle size, fractal dimension, and density of flocs gradually decrease, and the gap between flocs is larger than that at 60 °C. On this basis, the temperature model of overflow ultra-fine iron tailings is established according to the analysis of particle settling process, and the settling model was optimized according to different settling areas. The mean absolute error between the optimized settling velocity and the actual velocity is 0.007, the root mean square error is 0.002, and the error is small. The theoretical calculation results are in good agreement with the experimental data, and the optimized flocculation settling model has an important role in promoting the theoretical study of the flocculation settling of such ultra-fine iron mineral particles, and can be used to guide the sedimentation and separation system to achieve good sedimentation treatment effect under the best working conditions as required. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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Review
Vanadium: A Review of Different Extraction Methods to Evaluate Bioavailability and Speciation
Minerals 2022, 12(5), 642; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050642 - 20 May 2022
Viewed by 424
Abstract
The excessive input of heavy metals such as vanadium (V) into the environment has been one of the consequences of global industrial development. Excessive exposure to V can pose a potential threat to ecological safety and human health. Due to the heterogeneous composition [...] Read more.
The excessive input of heavy metals such as vanadium (V) into the environment has been one of the consequences of global industrial development. Excessive exposure to V can pose a potential threat to ecological safety and human health. Due to the heterogeneous composition and reactivity of the various elements in soils and sediments, quantitative analysis of the chemical speciation of V in different environmental samples is very complicated. The analysis of V chemical speciation can further reveal the bioavailability of V and accurately quantify its ecotoxicity. This is essential for assessing for exposure and for controlling ecological risks of V. Although the current investigation technologies for the chemical speciation of V have grown rapidly, the lack of comprehensive comparisons and systematic analyses of these types of technologies impedes a more comprehensive understanding of ecosystem safety and human health risks. In this review, we studied the chemical and physical extraction methods for V from multiple perspectives, such as technological, principle-based, and efficiency-based, and their application to the evaluation of V bioavailability. By sorting out the advantages and disadvantages of the current technologies, the future demand for the in situ detection of trace heavy metals such as V can be met and the accuracy of heavy metal bioavailability prediction can be improved, which will be conducive to development in the fields of environmental protection policy and risk management. Full article
(This article belongs to the Special Issue Concentration and Distribution of Heavy Metals in Soils)
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Article
Fluid Inclusion and Chemical Composition Characteristics of Emeralds from Rajasthan Area, India
Minerals 2022, 12(5), 641; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050641 - 20 May 2022
Viewed by 478
Abstract
Emerald is among the most valuable gems in the world. Over the past decade, its commercial value and geographic origin have been the focus of gemological and geological research. In this study, emerald samples from India were examined by UV-Vis-NIR, FTIR, Raman spectra [...] Read more.
Emerald is among the most valuable gems in the world. Over the past decade, its commercial value and geographic origin have been the focus of gemological and geological research. In this study, emerald samples from India were examined by UV-Vis-NIR, FTIR, Raman spectra analysis, EPMA, and LA-ICP-MS. Hexagonal three- and multi-phase inclusions are first reported in Indian emeralds, containing gas bubbles (CO2 or CO2 + CH4), water or liquid mixtures of H2O + CO2, and solid phases inclusions (rounded crystals of siderite and dolomite, platelets of phlogopite, and magnesite). Mineral inclusions in Indian emeralds typically included phlogopite, quartz, talc, aragonite, and albite. The representative UV-Vis-NIR spectra show a distinct Fe absorption band, and one of the more typical characteristics of Indian emeralds is that the absorption strength of Fe3+ (369 nm) and Fe2+ (851 nm) is greater than that of Cr3+ (426, 606, 635, and 680 nm). Infrared spectra show that the absorption of type II H2O is stronger than that of type I H2O. LA-ICP-MS results show that Indian emeralds contain high alkali metals (10,503–16,964 ppmw; avg. 13,942 ppmw), moderate Fe (2451–4153 ppmw; avg. 3468 ppmw), low V (37–122 ppmw; avg. 90 ppmw), and the content of Cr (106–6310 ppmw) varies in a wide range. From a greenish-white core to a medium-green rim, the content of Fe, V, Cr, Sc, Cs, Rb, and Ga gradually increases in emerald with color band. Full article
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Article
Analytical and Numerical Solution for Better Positioning in Mines with Potential Extending Application in Space Mining
Minerals 2022, 12(5), 640; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050640 - 19 May 2022
Viewed by 623
Abstract
Application of new technologies and operational methodologies in mining sector targets to obtain a beneficial outcome in the long term. Instrumentation and monitoring systems for shafts, underground tunneling, storing faculties, etc. are often automated. Implemented systems provide data of mines state, integrated enhanced [...] Read more.
Application of new technologies and operational methodologies in mining sector targets to obtain a beneficial outcome in the long term. Instrumentation and monitoring systems for shafts, underground tunneling, storing faculties, etc. are often automated. Implemented systems provide data of mines state, integrated enhanced protection, and early warning solutions. Navigation and positioning in mines are deemed to be unstable in parts of mining tunnels when the external reference points are very far apart, thus significantly increasing the error of the internal network. This paper demonstrates a simulation of an innovative analytical and numerical solution for better positioning in the mines, yielding to increased accuracy of the control points, while reducing the time needed for performing measurements. Based on real tunnel dimensions, different control network configurations are tested. Statistical analysis of simulated environments and virtual measurements, created by combining various instrumentation, confirms cm-level positioning accuracy. The innovative approach to a mine control network design is based on involving fixed-length bars in the network design, gaining in shorter measurements sessions, but keeping homogeneous accuracy throughout the network. The concept is tested on 27 simulated network configurations, combining network points distribution and measurement accuracy of distances and angles. Obtained results and statistical analysis prove that consistent cm-level accuracy can be expected within the network. Extending the concept to space mining, which is becoming an attractive destination for chasing the rare-earth elements (REEs), this methodology will be a spin-off for space exploration mainly applicable in the Lunar lava tube positioning, which are the most secure place to settle the new human life. Full article
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Article
A Kinetic Monte Carlo Approach to Model Barite Dissolution: The Role of Reactive Site Geometry
Minerals 2022, 12(5), 639; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050639 - 18 May 2022
Viewed by 398
Abstract
Barite (Ba[SO4]) is one of the promising candidates for sequestration of radioactive waste. Barite can incorporate radium (Ra) and form ideal solid solutions, i.e., (Ba,Ra)[SO4]. Together with isostructural celestite (Sr[SO4]), ternary solid solutions, (Ba,Sr,Ra)[SO4], may [...] Read more.
Barite (Ba[SO4]) is one of the promising candidates for sequestration of radioactive waste. Barite can incorporate radium (Ra) and form ideal solid solutions, i.e., (Ba,Ra)[SO4]. Together with isostructural celestite (Sr[SO4]), ternary solid solutions, (Ba,Sr,Ra)[SO4], may exist in natural conditions. Our fundamental understanding of the dissolution kinetics of isostructural sulfates is critically important for a better risk assessment of nuclear waste repositories utilizing this mineral for sequestration. So far, the barite-water interface has been studied with experimental methods and atomistic computer simulations. The direct connection between the molecular scale details of the interface structure and experimental observations at the microscopic scale is not yet well understood. Here, we began to investigate this connection by using a kinetic Monte Carlo approach to simulate the barite dissolution process. We constructed a microkinetic model for the dissolution process and identified the reactive sites. Identification of these sites is important for an improved understanding of the dissolution, adsorption, and crystal growth mechanisms at the barite–water interface. We parameterized the molecular detachment rates by using the experimentally observed etch pit morphologies and atomic step velocities. Our parameterization attempts demonstrated that local lattice coordination is not sufficient to differentiate between the kinetically important sites and estimate their detachment rates. We suggest that the water structure and dynamics at identified sites should substantially influence the detachment rates. However, it will require more work to improve the parameterization of the model by means of Molecular Dynamics and ab initio calculations. Full article
(This article belongs to the Special Issue Ion Adsorption at Mineral–Water Interfaces)
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Article
A Feasibility Study of CSEM in Geological Advance Forecast with Horizontal Casing Well
Minerals 2022, 12(5), 638; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050638 - 18 May 2022
Viewed by 371
Abstract
With the rapid exploitation of deep mines by digging new tunnels, the advance forecast of water inrush has become increasingly important. The land-based controlled source electromagnetic method (CSEM) is commonly used to detect water-bearing structures. To increase its sensitivity, we propose a new [...] Read more.
With the rapid exploitation of deep mines by digging new tunnels, the advance forecast of water inrush has become increasingly important. The land-based controlled source electromagnetic method (CSEM) is commonly used to detect water-bearing structures. To increase its sensitivity, we propose a new measuring configuration for CSEM by placing EM sensors in an underground steel-cased well. The numerical modeling is conducted by COMSOL to overcome the difficulties of investigating the feasibility of the measuring configuration. The current distribution and electromagnetic field along an in-seam horizontal casing are investigated based on a synthesis three-layered model. The results illustrate that the casing can be treated as antennas that enhance the electric fields at large depths. The water-bearing structures can be observed by a magnetic field (with a perpendicularly horizontal electric dipole (HED) source) rather than an electric field (with a parallelly HED source). Numerical simulations demonstrate that the proposed method is a feasible and effective technique for the detection of water-bearing structures during deep mineral exploration. Full article
(This article belongs to the Special Issue Electromagnetic Exploration: Theory, Methods and Applications)
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Article
Chemical Composition and Strontium Isotope Characteristics of Scheelite from the Doranasai Gold Deposit, NW China: Implications for Ore Genesis
Minerals 2022, 12(5), 637; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050637 - 18 May 2022
Viewed by 402
Abstract
Scheelite, as a common accessory mineral found in hydrothermal deposits, is an indicator that allows the study of the ore-forming hydrothermal process and the tracing of fluid sources. The Doranasai gold deposit is a large-sized orogenic gold deposit in the South Altai, and [...] Read more.
Scheelite, as a common accessory mineral found in hydrothermal deposits, is an indicator that allows the study of the ore-forming hydrothermal process and the tracing of fluid sources. The Doranasai gold deposit is a large-sized orogenic gold deposit in the South Altai, and orebodies occur as veins in the Devonian Tuokesalei Formation and Permian albite granite dykes. The ores are quartz veins and altered tectonites (rocks). Here, scheelite can be observed in the early-stage milky quartz veins, the middle-stage smoky quartz-polymetallic sulfide veins, and the altered albite granite dykes. In this study, the scheelites of these three types were carefully investigated in terms of texture, element, and isotope geochemistry to understand their ore-forming processes and fluid sources. The results showed that all types of scheelite were rich in Sr and poor in Mo, indicating that their ore-forming fluids had no genetic relation to magmatic–hydrothermal activities. The scheelites were characterized by the enrichment of medium rare earth element (MREE) and positive Eu anomaly in the chondrite-standardized REE patterns. This indicated the REE differentiation between scheelite and fluid, i.e., REE3+ and Na+ were in the form of valence compensation, preferentially replacing Ca2+ and selectively entering the scheelite lattice. The trace element composition of scheelite showed that the ore-forming fluid system was relatively closed, mesothermal, Na-rich, and reductive. The Sr isotope ratio of the scheelite (0.704819–0.70860, average 0.706372) was higher than that of the ore-bearing albite granite dyke (0.704654–0.704735), indicating that the Tuokesalei Formation is the main source for the fluids forming the Doranasai deposit. Full article
(This article belongs to the Special Issue Mineral Resources in North China Craton)
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Article
Alkali Recovery of Bauxite Residue by Calcification
Minerals 2022, 12(5), 636; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050636 - 17 May 2022
Viewed by 420
Abstract
Bauxite residue (red mud) generated during alumina production is a highly alkaline solid waste. The red mud is mainly stored on land, but it can cause harm to the surrounding environment and human health. The transformation of red mud into soil is a [...] Read more.
Bauxite residue (red mud) generated during alumina production is a highly alkaline solid waste. The red mud is mainly stored on land, but it can cause harm to the surrounding environment and human health. The transformation of red mud into soil is a feasible method for the large-scale disposal of red mud, but alkali removal is the key process that controls the transformation of red mud into soil. In this study, the calcification dealkalization of red mud with a small particle size was carried out below 100 °C. The results show that the sodium in red mud is predominately distributed in small particles, mainly because the lattice alkali and alkali present between the crystals are exposed to the surface of red mud particles by ball milling. The dealkalization process was controlled by the internal diffusion of the shrinking-core model (SCM), and the apparent activation energy was 23.55 kJ/mol. The dealkalization rate and the Na2O content of dealkalized red mud reached 92.44% and 0.61%, respectively. The dealkalization rate increased with increasing reaction time, reactant concentration, and leaching temperature, and this result was consistent with the results of the kinetic study. In addition, calcification enhances the flocculation of particles, so the filtration performance of red mud improved. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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Article
CO2-Water-Rock Interactions in Carbonate Formations at the Tazhong Uplift, Tarim Basin, China
Minerals 2022, 12(5), 635; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050635 - 17 May 2022
Viewed by 442
Abstract
The effects of CO2-water-rock interactions on the injectivity and safety of CO2 geological storage have drawn wide attention. The geochemical reaction mechanisms in carbonate formations after CO2 injection are still controversial. To better understand the transformation of injected CO [...] Read more.
The effects of CO2-water-rock interactions on the injectivity and safety of CO2 geological storage have drawn wide attention. The geochemical reaction mechanisms in carbonate formations after CO2 injection are still controversial. To better understand the transformation of injected CO2 in carbonates and the involved geochemical reactions, we first conducted autoclave experiments reproducing the in-situ conditions of the Lianglitage Formation, Yingshan Formation, and Qiulitage Formation at the Tazhong Uplift in the Tarim Basin. We then established a batch model using TOUGHREACT-ECO2H, validated with the experimental results, to simulate the long-term CO2-water-rock interactions. It was found that the initial mineral compositions and water chemistry have important effects on the CO2-water-rock interactions in carbonate formations. The experiment results show that the dissolution of calcite and dolomite dominates in the early reaction period. However, we still observed some secondary minerals, such as ankerite, montmorillonite, calcite, and dolomite. The CO2-water-rock reactions can be more dramatic when the contents of calcite and dolomite in carbonates are closer. Moreover, the long-term simulation results show that calcite, magnesite, and hematite are the main formed secondary minerals, whereas dolomite is the major dissolved mineral. This study is helpful for a better understanding of the CO2 mineral trapping mechanism in carbonate formations. Full article
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Article
Assessment of Operational Effectiveness of Innovative Circuit for Production of Crushed Regular Aggregates in Particle Size Fraction 8–16 mm
Minerals 2022, 12(5), 634; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050634 - 17 May 2022
Viewed by 347
Abstract
The purpose of this paper is to analyze a modern and unique technological system producing common aggregates at the Imielin Dolomite Mine. The installation was built on the basis of inventions of AGH UST and consists of an impact crusher, innovative screens WSR [...] Read more.
The purpose of this paper is to analyze a modern and unique technological system producing common aggregates at the Imielin Dolomite Mine. The installation was built on the basis of inventions of AGH UST and consists of an impact crusher, innovative screens WSR and WSL, light fraction separator SEL and hard fraction separator SET, low-pressure hydrocyclone NHC and infrastructure. The study was carried out on the crusher and screen on the example of production of aggregates with grain size 8–16 mm from dolomite, granite, limestone, sandstone, and gravel. The results showed that cubic aggregates with a low content of irregular grains of less than 1% can be produced in this technological system. Full article
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Article
Geochemical and Geochronological Constraints of Permian-Triassic Magmatism on Oceanic Subduction and Continental Collision during the Eastern Paleo-Tethyan Evolution
Minerals 2022, 12(5), 633; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050633 - 17 May 2022
Viewed by 449
Abstract
The Jinshajiang–Ailaoshan–Song Ma orogenic belt (JASB), as a vital segment of the eastern Paleo-Tethyan tectonic zone, is one of the most important zones in which to study the Paleo-Tethyan tectonic evolution. We have undertaken an integrated geochronological, petrological, and geochemical study of mafic [...] Read more.
The Jinshajiang–Ailaoshan–Song Ma orogenic belt (JASB), as a vital segment of the eastern Paleo-Tethyan tectonic zone, is one of the most important zones in which to study the Paleo-Tethyan tectonic evolution. We have undertaken an integrated geochronological, petrological, and geochemical study of mafic rocks from the JASB to reveal the subduction and closure processes of the eastern Paleo-Tethyan Ocean during the Permian to Triassic. In conjunction with previous magmatic and metamorphic records in the JASB, three important tectonic stages are identified: (1) Early Permian to Early Triassic (ca. 288–248 Ma). Most of the Early Permian to Early Triassic mafic rocks have normal mid-ocean ridge basalt (N-MORB)- or enriched MORB (E-MORB)-like rare earth elements (REE) and trace element-normalized patterns with positive εNd(t) and εHf(t) values and negative Nb and Ta anomalies. Their La/Nb ratios and εNd(t) values show that approximately 3%–15% of slab-derived fluid accounts for the generation of these rocks. These characteristics suggest that the mafic rocks formed in an arc/back-arc basin setting at this stage. Additionally, the Early Permian mafic rocks are mainly exposed in the Jomda–Weixi–Yaxuanqiao–Truong Son magmatic rock belt (JYTB) on the western side of the JASB, indicating that the westward subduction of the Jinshajiang–Ailaoshan–Song Ma Paleo-Tethys Ocean (JASO) began in the Early Permian. Middle Permian mafic rocks are exposed in the Ailaoshan-Day Nui Con Voi metamorphic complex belt and the JYTB on both sides of the JASB. We propose that the bipolar subduction of the JASO occurred in the Middle Permian and ended in the Early Triassic. (2) Middle Triassic (ca. 248–237 Ma). The mafic rocks at this stage have LREE- and LILE-enriched patterns, negative Nb and Ta anomalies and negative εNd(t) values. Their variable εHf(t), εNd(t) values and La/Nb ratios show that these mafic rocks were highly affected by crustal material (ca. 16%). Considering the Middle Triassic high-pressure (HP) metamorphism and massive Al-enriched felsic magmatism in the JASB, these rocks may have formed in a collisional setting between the South China Block (SCB) and the North Qiangtang–Simao–Indochina Block (QSIB) during the Middle Triassic. (3) Late Triassic (ca. 235–202 Ma). The mafic rocks at this stage have negative εNd(t) and εHf(t) values and show terrestrial array characteristics. The εNd(t) values and La/Nb ratios show that approximately 30% of crustal components account for the generation of these rocks. Combined with the contemporaneous bimodal magma and metamorphism during the Late Triassic, we suggest that these rocks may have formed in a postcollisional extensional setting associated with magma diapir. Full article
(This article belongs to the Special Issue Tectono-Magmatic Evolution and Metallogeny of Tethyan Orogenic Belts)
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Article
The Effect of the Concentration of Copper Ions on the Unfrozen Water Content in Bentonites Measured with the Use of DSC Method
Minerals 2022, 12(5), 632; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050632 - 17 May 2022
Viewed by 402
Abstract
Studies on changes of unfrozen water content in calcium bentonite from Slovakia, with various concentrations of copper ions, were carried out using the method of differential scanning calorimetry (DSC). In this study, the influence of molar concentration of copper(II) chloride solution (1 M, [...] Read more.
Studies on changes of unfrozen water content in calcium bentonite from Slovakia, with various concentrations of copper ions, were carried out using the method of differential scanning calorimetry (DSC). In this study, the influence of molar concentration of copper(II) chloride solution (1 M, 0.5 M, 0.25 M, 0.1 M), used to saturate clay, was analyzed, as well as the impact of copper ions contained in bentonite and how the copper concentration affects to changes of unfrozen water content versus temperature. The results suggest that new mineral phases originate in bentonite saturated with highly concentrated solutions due to the reaction with copper(II) chloride solutions. These minerals, identified based on XRD and SEM-EDS (X-ray Diffraction and Scanning Electron Microscopy with Energy Dispersive Spectroscopy) studies, are from the atacamite group. ANOVA (Analysis of Variance) has shown a statistically significant relationship between the unfrozen water content and the molar concentration of the solution used to saturate bentonite and between the unfrozen water content and the content of copper ions in the bentonite. The analysis of multiple regression has shown that the change of unfrozen water content in copper bentonites is related to the temperature change, specific surface, and the concentration of copper ions in the clay. An empirical equation was developed to estimate the content of unfrozen water at a given negative temperature in Cu-bentonites, in which the specific surface and copper ions concentration in the bentonite are the main parameters. Full article
(This article belongs to the Special Issue Application of Clays and Clay Minerals to Prevent Contamination)
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Article
Iron Ore Sinter Macro- and Micro-Structures, and Their Relationships to Breakage Characteristics
Minerals 2022, 12(5), 631; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050631 - 16 May 2022
Viewed by 452
Abstract
A systematic analysis of industrial iron ore sinter product and associated sinter returns was undertaken. The samples were characterised through identification of the major macro- and micro-structural types present in these materials. Examination of the breakage surfaces of the particles indicates a strong [...] Read more.
A systematic analysis of industrial iron ore sinter product and associated sinter returns was undertaken. The samples were characterised through identification of the major macro- and micro-structural types present in these materials. Examination of the breakage surfaces of the particles indicates a strong correlation between mechanical sinter strength and sinter microstructure. Preferential breakage was observed to occur in sinter materials having high porosity and those microstructures consisting of isolated hematite grains in a glass matrix. The bulk of the sinter product consisted of material with a microstructure of magnetite and silico-ferrite of calcium and aluminium (SFCA). The phases formed and the reaction sequences responsible for the formation of the principal microstructure types are explained by the non-equilibrium solidification of melts in the “Fe2O3”-Al2O3-CaO-SiO2 system. Full article
(This article belongs to the Special Issue Mineralogy of Iron Ore Sinters, Volume II)
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Article
A Methodology to Determine the Potential for Particulate Ore Sorting Based on Intrinsic Particle Properties
Minerals 2022, 12(5), 630; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050630 - 16 May 2022
Viewed by 445
Abstract
Sensor-based particulate ore sorting is a pre-concentration technique that sorts particles based on measurable physical properties, resulting in reduced energy consumption by removing waste prior to grinding. This study presents an integrated methodology to determine the potential for ore sorting based on intrinsic [...] Read more.
Sensor-based particulate ore sorting is a pre-concentration technique that sorts particles based on measurable physical properties, resulting in reduced energy consumption by removing waste prior to grinding. This study presents an integrated methodology to determine the potential for ore sorting based on intrinsic particle properties. The methodology first considers the intrinsic sortability based on perfect separation. Only intrinsically sortable ore is further assessed by determining the sensor-based sortability. The methodology is demonstrated using a case study based on a typical copper porphyry comminution circuit. The sorting duty identified for the case study was the removal of low-grade waste material from the pebble crusher stream at a suitable Cu cut-off grade. It was found that the ore had the potential to be sorted based on the intrinsic and ideal laboratory sensor sortability results but showed no potential to be sorted using industrial-scale sensors. The ideal laboratory XRF sensor results showed that around 40% of mass could be rejected as waste at copper recoveries above 80%. An economic analysis of the sortability tests showed that, at optimum separation conditions, the intrinsic, ideal sensor and industrial sensor sortability would result in an additional annual profit of ~$30 million, $21 million and $−7 million (loss), respectively. Full article
(This article belongs to the Special Issue Recent Developments in Mineral Processing at University of Cape Town)
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Article
Hyperspectral and Geochemical Analysis of Chlorites at the Gongchangling High-Grade Magnetite Deposit, NE China: Implications for Alteration Processes
Minerals 2022, 12(5), 629; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050629 - 15 May 2022
Viewed by 452
Abstract
The Gongchangling deposit is a representative banded iron formation (BIF) in China, in which developed several high-grade magnetite ores. The surrounding alteration rocks recorded the genesis information of the high-grade ores. However, the study related to alteration processes remains poor. In this study, [...] Read more.
The Gongchangling deposit is a representative banded iron formation (BIF) in China, in which developed several high-grade magnetite ores. The surrounding alteration rocks recorded the genesis information of the high-grade ores. However, the study related to alteration processes remains poor. In this study, we investigate the sub-types and formation temperature of chlorite using hyperspectral imaging and electronic probe microanalysis (EPMA), and deciphered the elemental migration trend during alteration processes by whole-rock geochemistry. The chlorites in the alteration rocks were divided into three sub-types according to the spectral features of the Fe-OH band near 2250 nm. The range of wavelength position is approximately 2250–2255 nm for chlorite-I, 2255–2260 nm for chlorite-II, and 2260–2265 nm for chlorite-III. The variation in Mg# is 0.32–0.44 in chlorite-I, 0.20–0.34 in chlorite-II, and 0.15–0.23 in chlorite-III, which is consistent with the range of wavelength position. The hydrothermal alteration resulted in the enrichment of iron and the depletion of silicon. The results shed new light on the recognition of chlorite sub-types and deciphered the hydrothermal alteration processes of high-grade magnetite ores, which proposed an effective method for mineralogical mapping. Full article
(This article belongs to the Special Issue Mapping of Rocks and Minerals Using Hyperspectral Remote Sensing)
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