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Minerals, Volume 10, Issue 7 (July 2020) – 68 articles

Cover Story (view full-size image): This paper analyses the mineralogical composition, texture and structure of a stalactite sampled from the city-wall storerooms of the Nueva Tabarca fortress (SE Spain). This speleothem presents an uncommon mineral assemblage: aragonite, brucite, gypsum, silica and halite. Internally, it shows a complex structure: 1) a central soda-straw composed by aragonite; 2) an external puff-pastry cone-crust formed preferentially by aragonite and brucite; and 3) an internal branching of coralloids, showing a subtle layering between brucite and aragonite. PHREEQC calculations showed that interaction between pore waters and the minerals of mortar aggregates of the city-wall (dolomite, pyroxene and amphibole) leads to rich-magnesium solutions. Evaporation modelling of lixiviated waters describes the precipitation of the mineral assemblage of the brucite–aragonite speleothems. View this paper
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Article
Investigations of Feldspar-Quartz Raw Materials After Firing: Effect of Various Na2O/K2O Ratio and Synthetic Pigments Addition
Minerals 2020, 10(7), 646; https://doi.org/10.3390/min10070646 - 21 Jul 2020
Viewed by 654
Abstract
Different techniques (chemical analysis, X-ray diffraction, Mössbauer spectroscopy, UV-Vis-NIR spectrophotometry and chromaticity measurements) were used to study the color variation of feldspathic raw materials after firing at 1200 °C. Two varieties of feldspar-quartz grits (with Na2O or K2O prevalence) [...] Read more.
Different techniques (chemical analysis, X-ray diffraction, Mössbauer spectroscopy, UV-Vis-NIR spectrophotometry and chromaticity measurements) were used to study the color variation of feldspathic raw materials after firing at 1200 °C. Two varieties of feldspar-quartz grits (with Na2O or K2O prevalence) doped with synthetic pigments (hematite and rutile) were heat-treated in an oxidizing atmosphere. The results obtained indicate that the color of the ceramic body after firing may not only depend on the presence and analytical content of coloring elements (such as iron and titanium), but on their valence state and the chemical characteristics of the melt itself. The prevalence of larger alkali K+ ions over Na+ ions may cause the reduction of the coordination number of iron. This has a significant effect on the length of the Fe–O bond, which in turn influences the capacity for light absorption of a specific wavelength. The results of spectrophotometric measurements showed pronounced disparity between the raw materials and samples doped with coloring oxides. The introduction of synthetic pigments caused clear changes in the spectral dependence of the total absorbance. The absorbance increased in the whole measuring range, in particular in the visible part of the spectrum. Furthermore, a red-shift of the absorption bands towards longer wavelengths attributed to oxygen-metal charge transfer (OMCT) interactions between Fe3+ and O2− ions as well as to d-d transitions within Fe3+ ions was observed. Full article
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Article
Phosphorus Species in Deep-Sea Carbonate Deposits: Implications for Phosphorus Cycling in Cold Seep Environments
Minerals 2020, 10(7), 645; https://doi.org/10.3390/min10070645 - 21 Jul 2020
Cited by 1 | Viewed by 799
Abstract
Phosphorus (P) is an important nutrient for biological communities in cold seeps. However, our knowledge on the source, species, and cycling of P in cold seep environments is limited. In this study, the concentration, species, and micro to nanometer scale distribution of P [...] Read more.
Phosphorus (P) is an important nutrient for biological communities in cold seeps. However, our knowledge on the source, species, and cycling of P in cold seep environments is limited. In this study, the concentration, species, and micro to nanometer scale distribution of P in seep carbonates were examined at three deep-sea cold seeps in the South China Sea and East China Sea. The Ca-P accounts for the largest proportion of P—followed by detrital-P, Fe-P, organic-P, and exchangeable-P. The distribution patterns of Ca-P, detrital-P, and organic-P in the seep carbonates differ from one another, as shown by elemental mapping with NanoSIMS and scanning electron microscopy. The covariation of P with Ca and C reveals that Ca-P co-precipitates with Ca-carbonate, which is linked to the process of sulfate-driven anaerobic oxidation of methane. Organic-P is also observed within biofilm-like organic carbon aggregates, revealing the microbial enrichment of P by fluids in the process of anaerobic oxidation of methane. P with a granulated morphology was identified as detrital-P derived from deep sediments. Most importantly, it is evident that Ca-P is positively correlated to the Fe content in all the seep carbonates. This indicates the likelihood that the dissolved P in cold-seep fluids is released primarily from Fe oxides through Fe-driven anaerobic oxidation of methane in deep sediments. These processes associated with different species of P may have significant implications for P geochemical cycling and anaerobic oxidation of methane impelled by Fe and sulfate reduction in cold seep environments. Full article
(This article belongs to the Section Mineral Deposits)
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Article
Ti-Magnetite Crystallization in Melt Inclusions of Trachytic Rocks from the Dokdo and Ulleung Islands, South Korea: Implications for Hydrous and Oxidized Magmatism
Minerals 2020, 10(7), 644; https://doi.org/10.3390/min10070644 - 20 Jul 2020
Viewed by 1030
Abstract
The Dokdo and Ulleung islands (Korea) are volcanic islands in the East Sea (Sea of Japan), formed in the late Cenozoic. These volcanic islands, in the back-arc basin of the Japanese archipelago, provide important information about magma characteristics in the eastern margin of [...] Read more.
The Dokdo and Ulleung islands (Korea) are volcanic islands in the East Sea (Sea of Japan), formed in the late Cenozoic. These volcanic islands, in the back-arc basin of the Japanese archipelago, provide important information about magma characteristics in the eastern margin of the Eurasian plate. The origin of the Dokdo and Ulleung intraplate volcanism is still controversial, and the role of fluids, especially water, in the magmatism is poorly understood. Here, we comprehensively analyzed the melt inclusions (10–100 m in diameter) hosted in clinopyroxene phenocrysts of trachyte, trachyandesite, and trachybasalt. In particular, we observed Ti-magnetite and amphibole which were crystallized as daughter mineral phases within melt inclusions, suggesting that Ti-magnetite was formed in an oxidized condition due to H2O dissociation and H2 diffusion. The Ti-magnetite exhibited compositional heterogeneities of MgO (average of 8.28 wt %), Al2O3 (average of 8.68 wt %), and TiO2 (average of 8.04 wt %). The positive correlation of TiO2 with Cr2O3 is probably attributed to evolutionary Fe–Ti-rich parent magma. Correspondingly, our results suggested hydrous and oxidized magmatism for the Dokdo and Ulleung volcanic islands. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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Article
Comparison of Detrital Zircon U-Pb and Muscovite 40Ar/39Ar Ages in the Yangtze Sediment: Implications for Provenance Studies
Minerals 2020, 10(7), 643; https://doi.org/10.3390/min10070643 - 20 Jul 2020
Cited by 3 | Viewed by 876
Abstract
Detrital zircon U-Pb and muscovite 40Ar/39Ar dating are useful tools for investigating sediment provenance and regional tectonic histories. However, the two types of data from same sample do not necessarily give consistent results. Here, we compare published detrital muscovite 40 [...] Read more.
Detrital zircon U-Pb and muscovite 40Ar/39Ar dating are useful tools for investigating sediment provenance and regional tectonic histories. However, the two types of data from same sample do not necessarily give consistent results. Here, we compare published detrital muscovite 40Ar/39Ar and zircon U-Pb ages of modern sands from the Yangtze River to reveal potential factors controlling differences in their provenance age signals. Detrital muscovite 40Ar/39Ar ages of the major tributaries and main trunk suggest that the Dadu River is a dominant sediment contributor to the lower Yangtze. However, detrital zircon data suggest that the Yalong, Dadu, and Min rivers are the most important sediment suppliers. This difference could be caused by combined effects of lower reaches dilution, laser spot location on zircons and difference in closure temperature and durability between muscovite and zircon. The bias caused by sediment laser spot targeting a core or rim of zircon and zircon reworking should be considered in provenance studies. Full article
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Article
Constraints on the Petrogenesis and Metallogenic Setting of Lamprophyres in the World-Class Zhuxi W–Cu Skarn Deposit, South China
Minerals 2020, 10(7), 642; https://doi.org/10.3390/min10070642 - 20 Jul 2020
Cited by 3 | Viewed by 738
Abstract
Whole-rock and apatite geochemical analyses and zircon U–Pb dating were carried out on the lamprophyres in the world-class Zhuxi W–Cu skarn deposit in northern Jiangxi, South China, in order to understand their origin of mantle sources and their relationship with the deposit, as [...] Read more.
Whole-rock and apatite geochemical analyses and zircon U–Pb dating were carried out on the lamprophyres in the world-class Zhuxi W–Cu skarn deposit in northern Jiangxi, South China, in order to understand their origin of mantle sources and their relationship with the deposit, as well as metallogenic setting. The results show the lamprophyres were formed at ca. 157 Ma, just before the granite magmatism and mineralization of the Zhuxi deposit. These lamprophyres have from 58.98–60.76 wt% SiO2, 2.52–4.96 wt% K2O, 5.92–6.41 wt% Fe2O3t, 3.75–4.19 wt% MgO, and 3.61–5.06 wt% CaO, and enrichment of light rare earth elements (LREE) and large-ion lithophile elements (LILE), and depletion of high-field-strength elements (HFSE). Apatites in the lamprophyres are enriched in LREE and LILE, Sr, S, and Cl, and have 87Sr/86Sr ratios ranging from 0.7076 to 0.7078. The conclusions demonstrate that the lithospheric mantle under the Zhuxi deposit was metasomatized during Neoproterozoic subduction. Late Jurassic crustal extension caused upwelling of the asthenospheric mantle and consecutively melted the enriched lithospheric mantle and then crustal basement, corresponding to the formation of lamprophyres and mineralization-related granites in the Zhuxi deposit, respectively. Full article
(This article belongs to the Special Issue Magmatic–Hydrothermal Alteration and Mineralizing Processes)
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Article
Cement Render and Mortar and Their Damages Due to Salt Crystallization in the Holy Trinity Church, Dominicans Monastery in Cracow, Poland
Minerals 2020, 10(7), 641; https://doi.org/10.3390/min10070641 - 20 Jul 2020
Cited by 3 | Viewed by 745
Abstract
The investigations focused on the façade of the 17th-century Myszkowskis chapel at the 13th-century Church of the Holy Trinity in Cracow, Poland. Most of the chapel’s façade is made of rusticated limestone blocks, but its lower part is covered with cement render, and [...] Read more.
The investigations focused on the façade of the 17th-century Myszkowskis chapel at the 13th-century Church of the Holy Trinity in Cracow, Poland. Most of the chapel’s façade is made of rusticated limestone blocks, but its lower part is covered with cement render, and the basement consists of irregular pieces of limestone and sandstone, bound and partly replaced with cement mortar. The façade exhibited clearly visible damages: gray soiling of the surface, cracks, scaling, and efflorescence. The study presents characteristics of the cement render and mortar used for stone repair and/or substitution, as well as efflorescence from the lower part of the Myszkowskis chapel façade. The materials were analyzed with optical microscopy, scanning electron microscopy (SEM-EDS), Raman microspectroscopy, X-ray diffractometry (XRPD), and mercury intrusion porosimetry. The analyses demonstrated that the render covering some of the decayed limestone blocks was prepared using Portland cement (residual clinker grains represent alite and belite) as a binding agent, mixed with crushed stone as an aggregate. The cement mortar consisted of rounded quartz grains, rock fragments, and feldspars in very fine-grained masses of calcite and gypsum, also containing relics of cement clinker (alite, belite, ferrite, and aluminate). All these components point out the use of the ordinary Portland cement. Analyses of the efflorescence allowed us to distinguish several secondary salts, among others, thenardite, aphthitalite, and darapskite. The appearance of these phases is related to the composition and physicochemical properties of the building materials, atmospheric alteration agents, air pollution, and some other anthropogenic factors. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
The State of Trace Elements (In, Cu, Ag) in Sphalerite Studied by X-Ray Absorption Spectroscopy of Synthetic Minerals
Minerals 2020, 10(7), 640; https://doi.org/10.3390/min10070640 - 20 Jul 2020
Cited by 4 | Viewed by 1068
Abstract
The oxidation state and local atomic environment of admixtures of In, Cu, and Ag in synthetic sphalerite crystals were determined by X-ray absorption spectroscopy (XAS). The sphalerite crystals doped with In, Cu, Ag, In–Cu, and In–Ag were synthesized utilizing gas transport, salt flux, [...] Read more.
The oxidation state and local atomic environment of admixtures of In, Cu, and Ag in synthetic sphalerite crystals were determined by X-ray absorption spectroscopy (XAS). The sphalerite crystals doped with In, Cu, Ag, In–Cu, and In–Ag were synthesized utilizing gas transport, salt flux, and dry synthesis techniques. Oxidation states of dopants were determined using X-ray absorption near edge structure (XANES) technique. The local atomic structure was studied by X-ray absorption fine structure spectroscopy (EXAFS). The spectra were recorded at Zn, In, Ag, and Cu K-edges. In all studied samples, In was in the 3+ oxidation state and replaced Zn in the structure of sphalerite, which occurs with the expansion of the nearest coordination shells due to the large In ionic radius. In the presence of In, the oxidation state of Cu and Ag is 1+, and both metals can form an isomorphous solid solution where they substitute for Zn according to the coupled substitution scheme 2Zn2+ ↔ Me+ + In3+. Moreover, Ag K-edges EXAFS spectra fitting, combined with the results obtained for In- and Au-bearing sphalerite shows that the Me-S distances in the first coordination shell in the solid solution state are correlated with the ionic radii and increase in the order of Cu < Ag < Au. The distortion of the atomic structure increases in the same order. The distant (second and third) coordination shells of Cu and Ag in sphalerite are split into two subshells, and the splitting is more pronounced for Ag. Analysis of the EXAFS spectra, coupled with the results of DFT (Density Function Theory) simulations, showed that the In–In and Me+–In3+ clustering is absent when the metals are present in the sphalerite solid solution. Therefore, all studied admixtures (In, Cu, Ag), as well as Au, are randomly distributed in the matrix of sphalerite, where the concentration of the elements in the “invisible” form can reach a few tens wt.%. Full article
(This article belongs to the Special Issue X-ray Absorption Spectroscopy of Synthetic and Natural Minerals)
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Article
Rietveld Analysis of Elpidite Framework Flexibility Using in Situ Powder XRD Data of Thermally Treated Samples
Minerals 2020, 10(7), 639; https://doi.org/10.3390/min10070639 - 19 Jul 2020
Cited by 2 | Viewed by 742
Abstract
The present study demonstrates the capabilities of the Rietveld procedure to track the structural transformations and framework flexibility on the example of the natural water-containing zirconosilicate elpidite, subjected (in bulk) to thermal treatment from room temperature to 300 °C. The methodological approach to [...] Read more.
The present study demonstrates the capabilities of the Rietveld procedure to track the structural transformations and framework flexibility on the example of the natural water-containing zirconosilicate elpidite, subjected (in bulk) to thermal treatment from room temperature to 300 °C. The methodological approach to the performed refinements and the obtained results are in accordance with the previously reported data from in situ single crystal X-ray diffraction studies on heated samples of the same mineral. More light has been drawn on the temperature interval in which the non-reconstructive topotactic phase transition occurs upon partial dehydration. The framework flexibility observed as a response to the water loss and subsequent thermal expansion was evaluated in terms of intentionally introduced set of geometric parameters characterizing the spatial orientation of symmetrically related zirconium octahedra in the structure, the coordination polyhedra volumes, their distortion indices, and bond angle variances. Full article
(This article belongs to the Special Issue The Rietveld Method in Geomaterials Characterisation)
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Article
Contribution to the Mineral Chemistry of the Proterozoic Aravalli Mafic Meta-Volcanic Rocks from Rajasthan, NW India
Minerals 2020, 10(7), 638; https://doi.org/10.3390/min10070638 - 18 Jul 2020
Cited by 1 | Viewed by 896
Abstract
Field, petrological and mineral chemistry for meta-volcanic rocks from the Aravalli sequence (Aravalli Craton, India) are presented. Field evidence such as volcanic flows and suspect pillow lava structures, dominant Fe-tholeiite lava flows intercalated with quartzites and argillaceous sediments, indicate rift tectonic environment. Primary [...] Read more.
Field, petrological and mineral chemistry for meta-volcanic rocks from the Aravalli sequence (Aravalli Craton, India) are presented. Field evidence such as volcanic flows and suspect pillow lava structures, dominant Fe-tholeiite lava flows intercalated with quartzites and argillaceous sediments, indicate rift tectonic environment. Primary mineralogy was obliterated during post-magmatic processes such as metamorphism corresponding to the greenschist to lower amphibolite facies conditions. The rock’s mineral composition was overprinted by plagioclase–chlorite–amphibole–epidote assemblage. The relicts of clinopyroxene were observed. The P-T estimation indicates a temperature of 550–600 °C for the pressure ranging from 3.0 to 7.0 kbar for the majority of amphiboles and 8.0–10.7 kbar for the minority. Geochemically, these rocks are komatiitic (picritic) and high-Fe tholeiitic basalts with 45.06−59.2 wt.% SiO2 and MgO content from 5 to 22.4 wt.% and Mg# of 17 to 71. They show large-ion lithophile elements (LILE) and light rare-earth elements (LREE) enrichment. Chondrite normalized rare-earth elements (REE) patterns for the Aravalli lava are moderately enriched with (La/Sm)N = 1.1−3.85, (La/Yb)N from 1.49 (komatiites) to 14.91 (komatiitic basalts). The trace element systematics with the negative Nb, P and Zr anomalies reflect their derivation from enriched sub-continental lithospheric sources, although minor crustal contamination cannot be ruled out. Aravalli rocks are considered to represent the transition from continental rift magmatism to shallow submarine eruption. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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Article
Influence of Titaniferous Phases on Tungsten Mineralizing Processes at the Giant Sisson Brook W-Mo Deposit, New Brunswick, Canada: Mineral-Chemical and Geochronological Assessment
Minerals 2020, 10(7), 637; https://doi.org/10.3390/min10070637 - 18 Jul 2020
Viewed by 714
Abstract
The Sisson Brook deposit is a low-grade, large-tonnage W-Mo deposit with notable Cu located in west-central New Brunswick, Canada, and is one of several W-Mo deposits in New Brunswick associated with fluids sourced from granitic plutons emplaced during the Devonian Acadian Orogeny. The [...] Read more.
The Sisson Brook deposit is a low-grade, large-tonnage W-Mo deposit with notable Cu located in west-central New Brunswick, Canada, and is one of several W-Mo deposits in New Brunswick associated with fluids sourced from granitic plutons emplaced during the Devonian Acadian Orogeny. The younger Devonian-aged stockwork and replacement scheelite-wolframite-molybdenite (and chalcopyrite) mineralization straddles the faulted boundary between Cambro-Ordovician metasedimentary rocks with Ordovician felsic volcaniclastic rocks and the Middle Silurian Howard Peak Granodiorite, with dioritic and gabbroic phases. U-Pb dating of magmatic titanite in the host dioritic phase of the Howard Peak Granodiorite using LA ICP-MS resulted in a 204Pb-corrected concordant age of 432.1 ± 1.9 Ma. Petrologic examination of selected mineralization combined with elemental mapping of vein selvages using micro-XRF and metasomatic titanite and ilmenite grains using LA ICP-MS indicates that saturation of titaniferous phases influenced the distribution of scheelite versus wolframite mineralization by altering the aFe/aCa ratio in mineralizing fluids. Ilmenite saturation in Ti-rich host rocks lowered the relative aFe/aCa and led to the formation of scheelite over wolframite. Altered magmatic titanite and hydrothermal titanite also show increased W and Mo concentrations due to interaction with and/or saturation from mineralizing fluids. Full article
(This article belongs to the Special Issue Magmatic–Hydrothermal Alteration and Mineralizing Processes)
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Article
β-Lactoglobulin Adsorption Layers at the Water/Air Surface: 4. Impact on the Stability of Foam Films and Foams
Minerals 2020, 10(7), 636; https://doi.org/10.3390/min10070636 - 17 Jul 2020
Cited by 4 | Viewed by 896
Abstract
The complexity and high sensitivity of proteins to environmental factors give rise to a multitude of variables, which affect the stabilization mechanisms in protein foams. Interfacial and foaming properties of proteins have been widely studied, but the reported unique effect of pH, which [...] Read more.
The complexity and high sensitivity of proteins to environmental factors give rise to a multitude of variables, which affect the stabilization mechanisms in protein foams. Interfacial and foaming properties of proteins have been widely studied, but the reported unique effect of pH, which can be of great interest to applications, has been investigated to a lesser extent. In this paper, we focus on the impact of pH on the stability of black foam films and corresponding foams obtained from solutions of a model globular protein—the whey β-lactoglobulin (BLG). Foam stability was analyzed utilizing three characteristic parameters (deviation time, transition time and half-lifetime) for monitoring the foam decay, while foam film stability was measured in terms of the critical disjoining pressure of film rupture. We attempt to explain correlations between the macroscopic properties of a foam system and those of its major building blocks (foam films and interfaces), and thus, to identify structure-property relationships in foam. Good correlations were found between the stabilities of black foam films and foams, while relations to the properties of adsorption layers appeared to be intricate. That is because pH-dependent interfacial properties of proteins usually exhibit an extremum around the isoelectric point (pI), but the stability of BLG foam films increases with increasing pH (3–7), which is well reflected in the foam stability. We discuss the possible reasons behind these intriguingly different behaviors on the basis of pH-induced changes in the molecular properties of BLG, which seem to be determining the mechanism of film rupture at the critical disjoining pressure. Full article
(This article belongs to the Special Issue Surfactants at Interfaces and Thin Liquid Films)
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Article
Gold in Irish Coal: Palaeo-Concentration from Metalliferous Groundwaters
Minerals 2020, 10(7), 635; https://doi.org/10.3390/min10070635 - 17 Jul 2020
Viewed by 1381
Abstract
Gold grains, up to 40 μm in size and containing variable percentages of admixed platinum, have been identified in coals from the Leinster Coalfield, Castlecomer, SE Ireland, for the first time. Gold mineralisation occurs in sideritic nodules in coals and in association with [...] Read more.
Gold grains, up to 40 μm in size and containing variable percentages of admixed platinum, have been identified in coals from the Leinster Coalfield, Castlecomer, SE Ireland, for the first time. Gold mineralisation occurs in sideritic nodules in coals and in association with pyrite and anomalous selenium content. Mineralisation here may have reflected very high heat flow in foreland basins north of the emerging Variscan orogenic front, responsible for gold occurrence in the South Wales Coalfield. At Castlecomer, gold (–platinum) is attributed to precipitation with replacive pyrite and selenium from groundwaters at redox interfaces, such as siderite nodules. Pyrite in the cores of the nodules indicates fluid ingress. The underlying Caledonian basement bedrock is mineralised by gold, and thus likely provided a source for gold. The combination of the gold occurrences in coal in Castlecomer and in South Wales, proximal to the Variscan orogenic front, suggests that these coals along the front could comprise an exploration target for low-temperature concentrations of precious metals. Full article
(This article belongs to the Collection Minerals in Coal and Coal Combustion Products)
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Article
Simultaneous Quantification of Forsterite Content and Minor–Trace Elements in Olivine by LA–ICP–MS and Geological Applications in Emeishan Large Igneous Province
Minerals 2020, 10(7), 634; https://doi.org/10.3390/min10070634 - 17 Jul 2020
Viewed by 727
Abstract
Olivine forsterite contents [Fo = 100 × Mg/(Mg + Fe) in mol%] and minor–trace element concentrations can aid our understanding of the Earth’s mantle. Traditionally, these data are obtained by electron probe microanalysis for Fo contents and minor elements, and then by laser [...] Read more.
Olivine forsterite contents [Fo = 100 × Mg/(Mg + Fe) in mol%] and minor–trace element concentrations can aid our understanding of the Earth’s mantle. Traditionally, these data are obtained by electron probe microanalysis for Fo contents and minor elements, and then by laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) for trace elements. In this study, we demonstrate that LA–ICP–MS, with a simplified 100% quantification approach, allows the calculation of Fo contents simultaneously with minor–trace elements. The approach proceeds as follows: (1) calculation of Fo contents from measured Fe/Mg ratios; (2) according to the olivine stoichiometric formula [(Mg, Fe)2SiO4] and known Fo contents, contents of Mg, Fe and Si can be computed, which are used as internal standards for minor–trace element quantification. The Fo content of the MongOLSh 11-2 olivine reference material is 89.55 ± 0.15 (2 s; N = 120), which agrees with the recommended values of 89.53 ± 0.05 (2 s). For minor–trace elements, the results matched well with the recommended values, apart from P and Zn data. This technique was applied to olivine phenocrysts in the Lijiang picrites from the Emeishan large igneous province. The olivine compositions suggest that the Lijiang picrites have a peridotitic mantle source. Full article
(This article belongs to the Special Issue Analytical Tools to Constrain the Origin of Minerals)
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Article
Effect of Ultrasound on the Oxidative Copper Leaching from Chalcopyrite in Acidic Ferric Sulfate Media
Minerals 2020, 10(7), 633; https://doi.org/10.3390/min10070633 - 17 Jul 2020
Cited by 4 | Viewed by 840
Abstract
The objective of this study is to compare the reaction kinetics of copper leaching from chalcopyrite in acidic ferric sulfate media with (UAL) and without (non-UAL) ultrasound assistance. Four leaching parameters were evaluated and optimized. The parameter with the strongest effect was temperature, [...] Read more.
The objective of this study is to compare the reaction kinetics of copper leaching from chalcopyrite in acidic ferric sulfate media with (UAL) and without (non-UAL) ultrasound assistance. Four leaching parameters were evaluated and optimized. The parameter with the strongest effect was temperature, followed by ultrasonic power, the solid-to-liquid ratio (S/L), and acid concentration. Copper recovery showed an increase with rising temperatures in both systems. Ultrasonic power had a positive effect on copper leaching, but no significant difference was found among various power amplitudes. Copper extraction increased with decreasing S/L. At 0.1% S/L, the UAL leaching rate was double the non-UAL leaching rate. In both systems, acid concentration had little effect on copper extraction. Under optimized conditions, 20% amplitude power, 1% S/L, 0.5 M acid, and 80 °C leaching temperature, copper extraction was 50.4% and 57.5% in the non-UAL and UAL treatments, respectively. Ultrasonic waves enhanced the leaching rate, shortened the reaction time, and reduced acid consumption. Analysis of the rate-controlling step using a shrinking core model showed that leaching occurs after diffusion through the product layer but also chemical controlled in both non-UAL and UAL systems. The leaching mechanism was confirmed by characterizing the chalcopyrite and leached residue with X-ray diffraction and scanning electron microscopy/energy dispersive X-ray spectroscopy. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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Article
Role of the Down-Bending Plate as a Detrital Source in Convergent Systems Revealed by U–Pb Dating of Zircon Grains: Insights from the Southern Andes and Western Italian Alps
Minerals 2020, 10(7), 632; https://doi.org/10.3390/min10070632 - 16 Jul 2020
Cited by 1 | Viewed by 651
Abstract
In convergent zones, several parts of the geodynamic system (e.g., continental margins, back-arc regions) can be deformed, uplifted, and eroded through time, each of them potentially delivering clastic sediments to neighboring basins. Tectonically driven events are mostly recorded in syntectonic clastic systems accumulated [...] Read more.
In convergent zones, several parts of the geodynamic system (e.g., continental margins, back-arc regions) can be deformed, uplifted, and eroded through time, each of them potentially delivering clastic sediments to neighboring basins. Tectonically driven events are mostly recorded in syntectonic clastic systems accumulated into different kinds of basins: trench, fore-arc, and back-arc basins in subduction zones and foredeep, thrust-top, and episutural basins in collisional settings. The most widely used tools for provenance analysis of synorogenic sediments and for unraveling the tectonic evolution of convergent zones are sandstone petrography and U–Pb dating of detrital zircon. In this paper, we present a comparison of previously published data discussing how these techniques are used to constrain provenance reconstructions and contribute to a better understanding of the tectonic evolution of (i) the Cretaceous transition from extensional to compressional regimes in the back-arc region of the southern Andean system; and (ii) the involvement of the passive European continental margin in the Western Alps subduction system during impending Alpine collision. In both cases, sediments delivered from the down-bending continental block are significantly involved. Our findings highlight its role as a detrital source, which is generally underestimated or even ignored in current tectonic models. Full article
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Petrogenesis and Tectonic Setting of the Highly Fractionated Junye Granitic Intrusion in the Yiliu Tungsten Polymetallic Deposit, Guangdong Province, South China: Constraints from Geochemistry and Sr-Nd-Pb-Hf Isotopes
Minerals 2020, 10(7), 631; https://doi.org/10.3390/min10070631 - 16 Jul 2020
Viewed by 745
Abstract
The Yiliu tungsten polymetallic deposit, located in the south central portion of the Nanling nonferrous metal metallogenic province in South China, is an area with common Yanshanian tectonothermal events. Early Yanshanian magmatism leads to the emplacement of voluminous tungsten-bearing granite intrusions, such as [...] Read more.
The Yiliu tungsten polymetallic deposit, located in the south central portion of the Nanling nonferrous metal metallogenic province in South China, is an area with common Yanshanian tectonothermal events. Early Yanshanian magmatism leads to the emplacement of voluminous tungsten-bearing granite intrusions, such as the Baoshan, Benggangling and Junye plutons, which are considered temporally and spatially associated with W-polymetallic mineralization in the Yiliu region. Here, we investigate the basic geological and petrological characteristics of the Junye granites, and present major and trace element geochemical data and bulk-rock Sr-Nd-Pb-Hf isotopic data to gain insight into the petrogenesis and tectonic setting of granitic intrusions in the region. The Junye granites are high-K calc-alkaline and metaluminous to weakly peraluminous [A/CNK = molar ratios of Al2O3/(CaO + Na2O + K2O) = 0.97–1.02] with enrichment in SiO2 (75.68–76.44 wt.%), relatively high total alkalis (K2O + Na2O = 8.06–8.45 wt.%) with K2O/Na2O ratios ranging from 1.12 to 1.42, and moderate Al2O3 (12.62–13.00 wt.%), but low in P2O5 (<0.01 wt.%), MgO (0.02–0.04 wt.%), CaO (0.78–0.95 wt.%) and Fe2O3T (0.93–1.07 wt.%). They show spectacular tetrad effect REE (rare earth element) patterns with low ΣREE content (53.2–145.3 ppm), negative Eu anomalies (δEu = 0.09–0.17) and slight enrichment of LREEs (light rare earth elements) relative to HREEs (heavy rare earth elements). The granites are enriched in Rb (481–860 ppm), Th (16.2–46.1 ppm) and U (25.4–40.8 ppm) but depleted in Ba (1.0–5.8 ppm), Sr (11.1–23.4 ppm), P (9.5–26.7 ppm) and Ti (241–393 ppm). All geochemical features lead us to interpret the Junye granites as highly fractionated I-type granites. These granites underwent intense interaction between highly evolved magma and volatile-rich hydrothermal fluids during the late stage of formation, and accompanied fractional crystallization of biotite, plagioclase and accessory minerals, such as apatite, monazite and allanite. Additionally, the granites show uniform Nd isotopic ratios with calculated εNd (152 Ma) values of −8.28 to −8.91 and Nd model age (TDM2) of 1645 to 1698 Ma, stable age-corrected initial Pb isotopic compositions with (206Pb/204Pb)i of 18.646–19.010, (207Pb/204Pb)i of 15.767–15.786 and (208Pb/204Pb)i of 39.113–39.159, respectively, and homogeneous Hf isotopic values yielding εHf (152 Ma) values from −6.9 to −9.5 with TDM2 ages of 1680 to 2214 Ma, collectively suggesting that the granitic magma was probably derived from the remelting of ancient infracrustal materials in the basement of the Nanling region. Consequently, we consider that the Junye granites are the products of partial melting of Paleoproterozoic infracrustal medium- to high-K metamorphic basaltic rocks in the Cathaysia Block, which was caused by the underplating of coeval mantle basaltic magmas that provided abundant heat energy for melting in a tectonic setting, with lithospheric extension and thinning during the late Jurassic period. Full article
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Article
A Method to Predict Water Recovery Rate in the Collection and Froth Zone of Flotation Systems
Minerals 2020, 10(7), 630; https://doi.org/10.3390/min10070630 - 16 Jul 2020
Viewed by 637
Abstract
This paper describes a method to predict water recovery rate into and through the foam in a bubble column operating under different gas rates, froth depths, and frother types and concentrations. Three frothers were considered: Metil Isobutil Carbinol (MIBC), a proprietary blend of [...] Read more.
This paper describes a method to predict water recovery rate into and through the foam in a bubble column operating under different gas rates, froth depths, and frother types and concentrations. Three frothers were considered: Metil Isobutil Carbinol (MIBC), a proprietary blend of alcohols, aldehydes, and esters commercialized under the name PINNACLE® 9891, and a PGE-based Dow Froth 1012 (DF1012). The water rate entering into the froth (foam) layer from the bubbly (collection) zone was estimated as the water rate overflowing the column when operating at a thin stable foam layer, i.e., 0.5 cm. It was observed that the rate at which water entered into the froth phase could be modelled as a unique linear function of the gas holdup below the froth, regardless of the frother chemistry. This is a fundamental result not previously found in the literature that also facilitates the calculation of the froth zone water recovery for deeper froths. The water recovery in the froth was found to be an inverse logarithmic function of the average liquid residence time in the froth. Although the same trend was observed for the three frothers tested, they did not converge into a single function, which suggests that frother chemistry plays a role in determining froth structure and then needs to be incorporated when modeling water transport in the froth. Finally, the water overflow rate calculated as the product of the water rate into the froth and froth water recovery predicted the actual measured values fairly well. The water transport model here proposed provides a simple representation of the interactions between collection and froth zone and its relation to easily measure operating variables. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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Article
U-Th-He Geochronology of Pyrite from the Uzelga VMS Deposit (South Urals)—New Perspectives for Direct Dating of the Ore-Forming Processes
Minerals 2020, 10(7), 629; https://doi.org/10.3390/min10070629 - 16 Jul 2020
Cited by 2 | Viewed by 813
Abstract
We report on the application of the U-Th-He method for the direct dating of pyrite and provide an original methodological approach for measurement of U, Th and He in single grains without loss of parent nuclides during thermal extraction of He. The U-Th-He [...] Read more.
We report on the application of the U-Th-He method for the direct dating of pyrite and provide an original methodological approach for measurement of U, Th and He in single grains without loss of parent nuclides during thermal extraction of He. The U-Th-He age of ten samples of high-crystalline stoichiometric pyrite from unoxidized massive ores of the Uzelga volcanogenic massive sulfide (VMS) deposit, South Urals, is 382 ± 12 Ma (2σ) (U concentrations ~1–5 ppm; 4He ~10−4 cm3 STP g−1). This age is consistent with independent (biostratigraphic) estimations of the age of ore formation (ca, 389–380 Ma) and is remarkably older than the probable age of the regional prehnite-pumpellyite facies metamorphism (~340–345 Ma). Our results indicate that the U-Th-He dating of ~1 mg weight pyrite sample is possible and open new perspectives for the dating of ore deposits. The relative simplicity of U-Th-He dating in comparison with other geochronological methods makes this approach interesting for further application. Full article
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Article
Incorporating Far-Infrared Data into Carbonate Mineral Analyses
Minerals 2020, 10(7), 628; https://doi.org/10.3390/min10070628 - 16 Jul 2020
Cited by 3 | Viewed by 804
Abstract
Polycrystalline carbonate minerals (including calcite, Mg-calcite, and aragonite) can show distinctive variations in their far-infrared (FIR) spectra. We describe how to identify mixed-phase samples by correlating FIR spectral changes with mid-infrared spectra, X-ray diffraction data, and simple peak overlap simulations. Furthermore, we show [...] Read more.
Polycrystalline carbonate minerals (including calcite, Mg-calcite, and aragonite) can show distinctive variations in their far-infrared (FIR) spectra. We describe how to identify mixed-phase samples by correlating FIR spectral changes with mid-infrared spectra, X-ray diffraction data, and simple peak overlap simulations. Furthermore, we show how to distinguish portlandite-containing (Ca(OH) 2 ) mixtures that are common in heated calcium carbonate samples. Ultimately, these results could be used for tracking how minerals are formed and how they change during environmental exposure or processing after extraction. Full article
(This article belongs to the Special Issue Texture and Microstructural Analysis of Crystalline Solids)
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Article
Mineralogical and Geochemical Characteristics of Lithium and Rare Earth Elements in High-Sulfur Coal from the Donggou Mine, Chongqing, Southwestern China
Minerals 2020, 10(7), 627; https://doi.org/10.3390/min10070627 - 15 Jul 2020
Cited by 2 | Viewed by 1010
Abstract
Coal and coal by-products are considered as the potential raw materials for critical elements (e.g., rare earth elements, Li, Ga, Ge, etc.), which have attracted much attention in recent years. The purpose of this study is to investigate the mineralogical and geochemical characteristics, [...] Read more.
Coal and coal by-products are considered as the potential raw materials for critical elements (e.g., rare earth elements, Li, Ga, Ge, etc.), which have attracted much attention in recent years. The purpose of this study is to investigate the mineralogical and geochemical characteristics, and controlling geological factors of lithium and rare earth elements in the Lopingian (Wujiaping Formation) coal from the Donggou Mine, southeastern Chongqing Coalfield, China. Results indicate that lithium and rare earth elements are significantly enriched in the Donggou coals, which could be new potential alternative sources for critical elements. Concentrations of lithium and rare earth elements in the Donggou coals gradually increase from top to bottom. Lithium is mainly associated with kaolinite, while rhabdophane, florencite, goyazite, and xenotime are the main hosts of rare earth elements. The controlling geological factor is the groundwater leaching of underlying tuff, and to a lesser extent, the terrigenous clastic materials input from the top layer of the Kangdian Upland. This study provides mineralization information for lithium and rare earth elements exploration in coal measures. Full article
(This article belongs to the Collection Minerals in Coal and Coal Combustion Products)
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Review
The Graphite Occurrences of Northern Norway, a Review of Geology, Geophysics, and Resources
Minerals 2020, 10(7), 626; https://doi.org/10.3390/min10070626 - 14 Jul 2020
Cited by 3 | Viewed by 1805
Abstract
There are three provinces in Northern Norway in which occurrences of graphite are abundant; the Island of Senja, the Vesterålen archipelago, and the Holandsfjorden area. From these provinces, we report graphite resources from 28 occurrences. We use a combination of airborne and ground [...] Read more.
There are three provinces in Northern Norway in which occurrences of graphite are abundant; the Island of Senja, the Vesterålen archipelago, and the Holandsfjorden area. From these provinces, we report graphite resources from 28 occurrences. We use a combination of airborne and ground geophysics to estimate the dimensions of the mineralized areas, and, combined with sampling and analysis of the graphite contents, this gives us inferred resources for almost all the occurrences. The average TC (total carbon) content is 11.6%, and the average size is 9.3 Mt or 0.8 Mt of contained graphite. We demonstrate that the Norwegian graphite occurrences have grades and tonnages of the same order of magnitude as reported elsewhere. The graphite-bearing rocks occur in a sequence that encompasses carbonates, meta-arenites, acid to intermediate pyroxene gneisses, and banded iron formations metamorphosed into the granulite facies. Available radiometric dating shows that the graphite-bearing rocks are predated by Archean gneisses and postdated by Proterozoic intrusions of granitic to intermediate compositions. Full article
(This article belongs to the Special Issue Graphite Deposits)
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Article
Crystallinity and Play-of-Colour in Gem Opal with Digit Patterns from Wegel Tena, Ethiopia
Minerals 2020, 10(7), 625; https://doi.org/10.3390/min10070625 - 13 Jul 2020
Cited by 1 | Viewed by 738
Abstract
A typical feature of Wegel Tena opal is the “digit pattern”. This pattern consists of two parts, columns and matrix, with different colours, transparency or play-of-colour effect, which is still unexplained. This study aims at investigating the various parts of the digit pattern [...] Read more.
A typical feature of Wegel Tena opal is the “digit pattern”. This pattern consists of two parts, columns and matrix, with different colours, transparency or play-of-colour effect, which is still unexplained. This study aims at investigating the various parts of the digit pattern using different spectroscopic methods, and scanning and transmission electron microscopy (SEM and TEM). The band at 780 cm−1 on the Fourier transform infrared (FTIR) spectrum is correlated to the symmetric stretching vibration of Si–O. The bands at 1085, 895, 785 and 3600 cm−1 on Raman spectra indicate that Wegel Tena opal is opal-CT. Comparison of the relative intensity of the Raman signals around 360 cm−1 indicates that the microcrystalline opal on the top of the sample contains a higher amount of tridymite-like structural units, and the tridymite-type regions in the matrix contain a higher degree of structural defects. Silica spheres in the columns tend to be smaller and better ordered than in the matrix. The diameter of the silica spheres (d = 80–500 nm) or agglomerates (d = 200–580 nm) in Wegel Tena opal satisfies the conditions of diffraction of visible light, and the thickness of the silica layer (h = 120–200 nm) satisfies the conditions for film interference. Full article
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Article
An Input-Output Analysis of the Economic Role and Effects of the Mining Industry in South Korea
Minerals 2020, 10(7), 624; https://doi.org/10.3390/min10070624 - 12 Jul 2020
Cited by 1 | Viewed by 925
Abstract
The mining industry (MI) has played a role in proving a stable supply of minerals for industrial production and human survival. The South Korean government is implementing various policies to promote the MI and needs quantitative information on the economic role and effects [...] Read more.
The mining industry (MI) has played a role in proving a stable supply of minerals for industrial production and human survival. The South Korean government is implementing various policies to promote the MI and needs quantitative information on the economic role and effects of the MI. Thus, this article aims to derive the information through an input-output (IO) analysis using the recently published 2015 IO table, subdividing the MI into four sectors, namely coal, crude petroleum and natural gas, metal ores, and non-metallic mineral mining, and treating the MI as exogenous rather than endogenous. To this end, three models are employed. First, the production-inducing effects, value-added creation effects, and wage-inducing effects of 1 dollar of production in the MI sector are analyzed using a demand-driven model. One dollar of production or investment in the sector causes 1.81 of production, 0.85 dollar of value-added, and 0.33 dollar of wage, respectively. Second, by applying a supply-driven model, it is found that one dollar of supply shortage in the MI causes 2.24 dollars of production failure throughout the national economy. Third, by utilizing a price-side model, it is discovered that a 10% increase in the price of output of the MI raises the overall price level by 0.025%. Full article
Article
Tellurium Minerals: Structural and Chemical Diversity and Complexity
Minerals 2020, 10(7), 623; https://doi.org/10.3390/min10070623 - 12 Jul 2020
Cited by 2 | Viewed by 779
Abstract
The chemical diversity and complexity of tellurium minerals were analyzed using the concept of mineral systems and Shannon informational entropy. The study employed data for 176 Te mineral species known today. Tellurium minerals belong to six mineral systems in the range of one-to-six [...] Read more.
The chemical diversity and complexity of tellurium minerals were analyzed using the concept of mineral systems and Shannon informational entropy. The study employed data for 176 Te mineral species known today. Tellurium minerals belong to six mineral systems in the range of one-to-six species-defining elements. For 176 tellurium minerals, only 36 chemical elements act as essential species-defining constituents. The numbers of minerals of main elements are calculated as follows (the number of mineral species is given in parentheses): O (89), H (48), Cu (48), Pb (43), Bi (31), S (29), Ag (20), Fe (20), Pd (16), Cl (13), and Zn (11). In accordance with their chemistry, all Te minerals are classified into five types of mineral systems: tellurium, oxides, tellurides and intermetalides, tellurites, and tellurates. A statistical analysis showed positive relationships between the chemical, structural, and crystallochemical complexities and the number of essential species-defining elements in a mineral. A positive statistically significant relationship between chemical and structural complexities was established. It is shown that oxygen-free and oxygen-bearing Te minerals differ sharply from each other in terms of chemical and structural complexity, with the first group of minerals being simpler than the second group. The oxygen-free Te minerals (tellurium, tellurides, and intermetallides) are formed under reducing conditions with the participation of hydrothermal solutions. The most structurally complex oxygen-bearing Te minerals originate either from chemical weathering and the oxidation of ore deposits or from volcanic exhalations (Nabokoite). Full article
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Article
Pyrite Varieties at Pobeda Hydrothermal Fields, Mid-Atlantic Ridge 17°07′–17°08′ N: LA-ICP-MS Data Deciphering
Minerals 2020, 10(7), 622; https://doi.org/10.3390/min10070622 - 12 Jul 2020
Cited by 6 | Viewed by 1135
Abstract
The massive sulfide ores of the Pobeda hydrothermal fields are grouped into five main mineral microfacies: (1) isocubanite-pyrite, (2) pyrite-wurtzite-isocubanite, (3) pyrite with minor isocubanite and wurtzite-sphalerite microinclusions, (4) pyrite-rich with framboidal pyrite, and (5) marcasite-pyrite. This sequence reflects the transition from feeder [...] Read more.
The massive sulfide ores of the Pobeda hydrothermal fields are grouped into five main mineral microfacies: (1) isocubanite-pyrite, (2) pyrite-wurtzite-isocubanite, (3) pyrite with minor isocubanite and wurtzite-sphalerite microinclusions, (4) pyrite-rich with framboidal pyrite, and (5) marcasite-pyrite. This sequence reflects the transition from feeder zone facies to seafloor diffuser facies. Spongy, framboidal, and fine-grained pyrite varieties replaced pyrrhotite, greigite, and mackinawite “precursors”. The later coarse and fine banding oscillatory-zoned pyrite and marcasite crystals are overgrown or replaced by unzoned subhedral and euhedral pyrite. In the microfacies range, the amount of isocubanite, wurtzite, unzoned euhedral pyrite decreases versus an increasing portion of framboidal, fine-grained, and spongy pyrite and also marcasite and its colloform and radial varieties. The trace element characteristics of massive sulfides of Pobeda seafloor massive sulfide (SMS) deposit are subdivided into four associations: (1) high temperature—Cu, Se, Te, Bi, Co, and Ni; (2) mid temperature—Zn, As, Sb, and Sn; (3) low temperature—Pb, Sb, Ag, Bi, Au, Tl, and Mn; and (4) seawater—U, V, Mo, and Ni. The high contents of Cu, Co, Se, Bi, Te, and values of Co/Ni ratios decrease in the range from unzoned euhedral pyrite to oscillatory-zoned and framboidal pyrite, as well as to colloform and crystalline marcasite. The trend of Co/Ni values indicates a change from hydrothermal to hydrothermal-diagenetic crystallization of the pyrite. The concentrations of Zn, As, Sb, Pb, Ag, and Tl, as commonly observed in pyrite formed from mid- and low-temperature fluids, decline with increasing crystal size of pyrite and marcasite. Coarse oscillatory-zoned pyrite crystals contain elevated Mn compared to unzoned euhedral varieties. Framboidal pyrite hosts maximum concentrations of Mo, U, and V probably derived from ocean water mixed with hydrothermal fluids. In the Pobeda SMS deposit, the position of microfacies changes from the black smoker feeder zone at the base of the ore body, to seafloor marcasite-pyrite from diffuser fragments in sulfide breccias. We suggest that the temperatures of mineralization decreased in the same direction and determined the zonal character of deposit. Full article
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Article
Development of Ceramic Materials for the Manufacture of Bricks with Stone Cutting Sludge from Granite
Minerals 2020, 10(7), 621; https://doi.org/10.3390/min10070621 - 10 Jul 2020
Cited by 1 | Viewed by 933
Abstract
The manufacture of bricks for building purposes consumes large quantities of virgin materials, such as clay. On the other hand, the ornamental stone processing industry produces a huge amount of stone cutting sludge in its process. Therefore, this study presents the development of [...] Read more.
The manufacture of bricks for building purposes consumes large quantities of virgin materials, such as clay. On the other hand, the ornamental stone processing industry produces a huge amount of stone cutting sludge in its process. Therefore, this study presents the development of ceramic materials for the manufacture of bricks with stone cutting sludges, more specifically from granite. For this purpose, the physical properties of the stone cutting sludge and the chemical composition were mainly analyzed. Subsequently, different groups of ceramic samples were conformed and sintered with various combinations of clay and of stone cutting sludges. The conformed samples were evaluated with different physical tests and with the compressive strength test. The addition of stone cutting sludges to the ceramics reflected the creation of a material with lower density and higher porosity. The compressive strength of the different groups reflected a maximum allowable percentage of stone cutting sludges incorporation of 70%. Therefore, ceramic materials were developed with stone cutting sludges, developing a sustainable, lighter material with acceptable mechanical and physical characteristics. Avoiding the deposition of a polluting waste in a landfill and at the same time avoiding the extraction of new virgin materials. Full article
(This article belongs to the Special Issue Reutilization and Valorization of Mine Waste)
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Article
Characterization of Weathering Processes of the Giant Copper Deposit of Tizert (Igherm Inlier, Anti-Atlas, Morocco)
Minerals 2020, 10(7), 620; https://doi.org/10.3390/min10070620 - 10 Jul 2020
Cited by 4 | Viewed by 1411
Abstract
The giant Tizert copper deposit is considered as the largest copper resource in the western Anti-Atlas (Morocco). The site is characterized by Cu mineralization carried by malachite, chalcocite, covellite, bornite and chalcopyrite; azurite is not observed. The host rocks are mainly limestones (Formation [...] Read more.
The giant Tizert copper deposit is considered as the largest copper resource in the western Anti-Atlas (Morocco). The site is characterized by Cu mineralization carried by malachite, chalcocite, covellite, bornite and chalcopyrite; azurite is not observed. The host rocks are mainly limestones (Formation of Tamjout Dolomite) and sandstones/siltstones (Basal Series) of the Ediacaran/Cambrian transition. The supergene enrichment is most likely related to episodes of uplift/doming (last event since 30 Ma), which triggered the exhumation of primary/hypogene mineralization (chalcopyrite, pyrite, galena, chalcocite I and bornite I), generating their oxidation and the precipitation of secondary/supergene sulfides, carbonates and Fe-oxyhydroxides. The Tizert supergene deposit mainly consists of (i) a residual patchwork of laterite rich in Fe-oxyhydroxides; (ii) a saprolite rich in malachite, or “green oxide zone” where primary structures such as stratification are preserved; (iii) a cementation zone containing secondary sulfides (covellite, chalcocite II and bornite II). The abundance of Cu carbonates results from the rapid neutralization of acidic meteoric fluids, due to oxidation of primary sulfides, by carbonate host rocks. Chlorite is also involved in the neutralization processes in the sandstones/siltstones of the Basal Series, in which supergene clays, such as kaolinite and smectites, subsequently precipitated. At Tizert, as can be highlighted in other supergene Cu-deposits around the world, azurite is absent due to low pCO2 and relatively high pH conditions. In addition to copper, Ag enrichment is also observed in weathered rocks; Fe-oxyhydroxides contain high Zn, As, and Pb contents. However, these secondary enrichments are quite low compared to Cu in the whole Tizert site, which is therefore, considered as relatively homogeneous. Full article
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Article
An Improvement on Selective Separation by Applying Ultrasound to Rougher and Re-Cleaner Stages of Copper Flotation
Minerals 2020, 10(7), 619; https://doi.org/10.3390/min10070619 - 09 Jul 2020
Cited by 7 | Viewed by 1077
Abstract
It has been known that the power ultrasound is used as a pretreatment and rarely applied as a simultaneous method to improve grade and recovery during froth flotation processes. This work aimed at investigating the impact of simultaneously used ultrasonic waves under variant [...] Read more.
It has been known that the power ultrasound is used as a pretreatment and rarely applied as a simultaneous method to improve grade and recovery during froth flotation processes. This work aimed at investigating the impact of simultaneously used ultrasonic waves under variant operating configurations on the flotation of representative porphyry copper ore during rougher and re-cleaner stages. For this purpose, four different operating outlines were examined as (I) conventional flotation, (II) homogenizer, (III) ultrasonic bath, and (IV) combination of a homogenizer and an ultrasonic bath. The ultrasonic vibration was generated by the homogenizer (21 kHz, 1 kW) in the froth zone and ultrasonic bath (35 kHz, 0.3 kW) in the bulk zone. The rougher and re-cleaner flotation experiments were conducted using Denver-type mechanically agitated cells with 4.2 and 1 L capacities, respectively. The results showed that using the homogenizer (at 0.4 kW) slightly affected the selectivity separation index of chalcopyrite and pyrite, although it positively increased the grade of chalcopyrite from 21.5% to 25.7%. The ultrasonic-assisted flotation experiments with the ultrasonic bath and its combination with the homogenizer (0.4 kW) (i.e., configurations III and IV) led to an increase of approximately 16.1% and 26.9% in the chalcopyrite selectivity index compared to the conventional flotation, respectively. At the cleaning stage, a lower grade of aluminum silicate-based minerals was obtained desirably in every ultrasonic-treated configuration, which was supported with the water recoveries. Finally, applying the homogenizer and its combination with the ultrasonic bath were recommended for re-cleaner and rougher stages, respectively. Further fundamental and practical knowledge gaps required to be studied were highlighted. Full article
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Article
Zircon U-Pb Dating and Petrogenesis of Multiple Episodes of Anatexis in the North Dabie Complex Zone, Central China
Minerals 2020, 10(7), 618; https://doi.org/10.3390/min10070618 - 09 Jul 2020
Cited by 1 | Viewed by 897
Abstract
The North Dabie complex zone (NDZ), central China, is a high-T ultrahigh-pressure (UHP) metamorphic terrane. It underwent a complex evolution comprising of multistage metamorphism and multiple anatectic events during the Mesozoic continental collision, characterized by granulite-facies overprinting and a variety of migmatites with [...] Read more.
The North Dabie complex zone (NDZ), central China, is a high-T ultrahigh-pressure (UHP) metamorphic terrane. It underwent a complex evolution comprising of multistage metamorphism and multiple anatectic events during the Mesozoic continental collision, characterized by granulite-facies overprinting and a variety of migmatites with different generations of leucosomes. In this contribution, we carried out an integrated study including field investigation, petrographic observations, zircon U-Pb dating, and whole-rock element and Sr-Nd-Pb isotope analysis for the migmatites in the NDZ and their leucosomes and melanosomes. As a result, four groups of leucosomes have been recognized: Group 1 (garnet-bearing leucosome), strongly deformed leucosomes with coarse-grained peritectic garnet; Group 2 (amphibole-rich leucosome), weakly deformed to undeformed amphibole-rich leucosomes with coarse-grained peritectic amphibole and no garnet; Group 3 (amphibole-poor leucosome), weakly deformed to undeformed amphibole-poor leucosomes with minor fine-grained amphibole; Group 4 (K-feldspar-rich leucosome), K-feldspar-rich leucosomes mainly composed of coarse-grained quartz, plagioclase and K-feldspar. Zircon SHRIMP and LA-ICPMS U-Pb dating suggest that the Group 1 leucosomes formed at 209 ± 2 Ma whereas the rest of the leucosome groups (Groups 2–4) occurred between 145–110 Ma, in response to decompression under granulite-facies conditions during the early stage of exhumation, and to heating during post-orogenic collapse, respectively. Furthermore, the garnet-bearing leucosomes were resulted from fluid-absent anatexis related to biotite dehydration melting, while the other three groups of leucosomes were formed during large-scale fluid-present partial melting and coeval migmatization. This migmatization comes from heating from the mountain-root removal and asthenosphere upwelling, together with the influx of fluids derived from country rocks at mid-upper crustal levels. However, all the leucosomes and melanosomes display Pb-isotopic compositions similar to those observed for the NDZ UHP rocks (eclogites and granitic gneisses), suggesting a common source from the Triassic subducted Neoproterozoic lower-crustal rocks. In addition, the Cretaceous partial melting and migmatization began at 143 ± 2 Ma with three age-peaks at 133 ± 3 Ma, 124 ± 3 Ma and 114 ± 7 Ma, respectively. Full article
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Article
Experimental Procedure for the Determination of the Critical Coalescence Concentration (CCC) of Simple Frothers
Minerals 2020, 10(7), 617; https://doi.org/10.3390/min10070617 - 09 Jul 2020
Cited by 5 | Viewed by 971
Abstract
In this study, the critical coalescence concentrations (CCC) of selected commercial frother solutions, namely polypropylene glycols (PPG 200, 400, and 600), tri propylene glycol (BTPG), triethylene glycol (BTEG), dipropylene glycol (BDPG), and as a reference, methyl isobutyl carbinol (MIBC), were determined using a [...] Read more.
In this study, the critical coalescence concentrations (CCC) of selected commercial frother solutions, namely polypropylene glycols (PPG 200, 400, and 600), tri propylene glycol (BTPG), triethylene glycol (BTEG), dipropylene glycol (BDPG), and as a reference, methyl isobutyl carbinol (MIBC), were determined using a bubble column based on light absorption. The results for all seven frothers showed that BTEG has the worst bubble inhibiting performance, and PPG 600 has the best bubble inhibiting performance. While critical coalescence concentration (CCC) was found as 3 ppm for PPG 600, it increased to 25 ppm for BTEG. In the case of MIBC, which was the reference point, the CCC value was found as 10 ppm, which was consistent with the literature. The surface tension isotherms of the frothers were determined and analyzed with one of the latest adsorption models. The results indicated that the polypropylene glycol frothers showed more surface activity compared to alcohol or other frothers investigated. This is due to the additional reorganization of the PPG molecules on the air/water interface, thus boosting its surface activity. Full article
(This article belongs to the Special Issue Surfactants at Interfaces and Thin Liquid Films)
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