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Minerals, Volume 11, Issue 5 (May 2021) – 110 articles

Cover Story (view full-size image): Geological carbon capture and sequestration (CCS) can reduce the overall carbon footprint of human activities. One important issue affecting the long-term success of CCS operations is the degradation of cement wellbore casings due to carbonation reactions in the underground CO2 storage environment. We use ab initio molecular dynamic (AIMD) simulations to quantitatively explore the reactivity of supercritical CO2 with the surfaces of portlandite—a model hydrated cement phase. CO2 undergoes a concerted reaction with H2O and surface –OH groups to form bicarbonate complexes. The free-energy barriers of their formation are controlled by the molecular structure of the surface water layer, which is, in turn, dictated by the surface chemistry and the degree of nanoconfinement. View this paper
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Article
Unusual Perforations in Phlogopite Crystals from Caldara di Manziana (Italy) Caused by Sulphuric Acid Generated by Microbial Oxidation of H2S Emanations
Minerals 2021, 11(5), 547; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050547 - 20 May 2021
Viewed by 623
Abstract
Phlogopite flakes strewn on the soil of Caldara di Manziana (Italy) display multiple minute perforations. The site is a caldera linked to recent volcanism (90 ka to 0.8 Ma) with present emanations of CO2 (~150 t d−1) and H2 [...] Read more.
Phlogopite flakes strewn on the soil of Caldara di Manziana (Italy) display multiple minute perforations. The site is a caldera linked to recent volcanism (90 ka to 0.8 Ma) with present emanations of CO2 (~150 t d−1) and H2S (~2.55 t d−1). Stereomicroscopy and SEM–EDX observation of the phlogopite crystals shows holes and depressions <200 µm to 2 mm across. They are circular, pseudo-hexagonal, or irregular. Within the depressions, there are deposits of phlogopite alteration products consistent with a sulphuric acid attack, showing loss of Mg and K. Some are thin and homogeneous; others are thick, irregular, and chemically heterogeneous, including plates, flakes, tubes of Fe-beidellite or Fe-bearing halloysite, silica, Fe oxides, and gypsum. Areas of phlogopite surface are also altered. Sulphuric acid is produced from the H2S gas by the mediation of sulphur-oxidizing bacteria. Pseudo-hexagonal perforations are interpreted to result from slow acid attack with dissolution controlled by phlogopite crystal symmetry. Some depressions developed surrounding films of pseudo-hexagonal shape, interpreted as jarosite crystallizing radially outwards from the depressions. This style of acid attack is possibly promoted by local high humidity and precipitation that generate long-lived water droplets and films on mineral surfaces where sulphuric acid is active for prolonged times. Full article
(This article belongs to the Special Issue Clay Minerals–Life Interplay)
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Article
Lead Recovery from Solid Residues of Copper Industry Using Triethylenetetramine Solution
Minerals 2021, 11(5), 546; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050546 - 20 May 2021
Cited by 1 | Viewed by 872
Abstract
Industrial processing of mineral ores and concentrates generates large amounts of solid residues, which can be landfilled or further processed to recover selected elements depending on its economical profitability. Pressure leaching is a technology enabling high recovery of base metals like copper and [...] Read more.
Industrial processing of mineral ores and concentrates generates large amounts of solid residues, which can be landfilled or further processed to recover selected elements depending on its economical profitability. Pressure leaching is a technology enabling high recovery of base metals like copper and zinc, transferring others like lead and iron to the solid residue. High temperature and pressure of such leaching leads to formation of sparingly soluble lead jarosite (plumbojarosite). The load of lead landfilled as solid residues resulting from such operation is so big that its recovery is perspective and crucial for waste-limiting technologies. This paper is devoted to lead extraction from pressure leaching residues using triethylenetetramine solution and then its precipitation as a commercial lead carbonate. The highest obtained recovery of lead was 91.3%. Additionally, presented technology allows to manage and recycle amine solution and reuse solid products. Produced pure lead carbonate can be directly added to smelting, not increasing temperature within the furnace. Full article
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Article
Tamuraite, Ir5Fe10S16, a New Species of Platinum-Group Mineral from the Sisim Placer Zone, Eastern Sayans, Russia
Minerals 2021, 11(5), 545; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050545 - 20 May 2021
Viewed by 1340
Abstract
Tamuraite, ideally Ir5Fe10S16, occurs as discrete phases (≤20 μm) in composite inclusions hosted by grains of osmium (≤0.5 mm across) rich in Ir, in association with other platinum-group minerals in the River Ko deposit of the Sisim [...] Read more.
Tamuraite, ideally Ir5Fe10S16, occurs as discrete phases (≤20 μm) in composite inclusions hosted by grains of osmium (≤0.5 mm across) rich in Ir, in association with other platinum-group minerals in the River Ko deposit of the Sisim Placer Zone, southern Krasnoyarskiy Kray, Russia. In droplet-like inclusions, tamuraite is typically intergrown with Rh-rich pentlandite and Ir-bearing members of the laurite–erlichmanite series (up to ~20 mol.% “IrS2”). Tamuraite is gray to brownish gray in reflected light. It is opaque, with a metallic luster. Its bireflectance is very weak to absent. It is nonpleochroic to slightly pleochroic (grayish to light brown tints). It appears to be very weakly anisotropic. The calculated density is 6.30 g·cm−3. The results of six WDS analyses are Ir 29.30 (27.75–30.68), Rh 9.57 (8.46–10.71), Pt 1.85 (1.43–2.10), Ru 0.05 (0.02–0.07), Os 0.06 (0.03–0.13), Fe 13.09 (12.38–13.74), Ni 12.18 (11.78–13.12), Cu 6.30 (6.06–6.56), Co 0.06 (0.04–0.07), S 27.23 (26.14–27.89), for a total of 99.69 wt %. This composition corresponds to (Ir2.87Rh1.75Pt0.18Ru0.01Os0.01)Σ4.82(Fe4.41Ni3.90Cu1.87Co0.02)Σ10.20S15.98, calculated based on a total of 31 atoms per formula unit. The general formula is (Ir,Rh)5(Fe,Ni,Cu)10S16. Results of synchrotron micro-Laue diffraction studies indicate that tamuraite is trigonal. Its probable space group is R3m (#166), and the unit-cell parameters are a = 7.073(1) Å, c = 34.277(8) Å, V = 1485(1) Å3, and Z = 3. The c:a ratio is 4.8462. The strongest eight peaks in the X-ray diffraction pattern [d in Å(hkl)(I)] are: 3.0106(216)(100), 1.7699(420)(71), 1.7583(2016)(65), 2.7994(205)(56), 2.9963(1010)(50), 5.7740(102)(45), 3.0534(201)(43) and 2.4948(208)(38). The crystal structure is derivative of pentlandite and related to that of oberthürite and torryweiserite. Tamuraite crystallized from a residual melt enriched in S, Fe, Ni, Cu, and Rh; these elements were incompatible in the Os–Ir alloy that nucleated in lode zones of chromitites in the Lysanskiy layered complex, Eastern Sayans, Russia. The name honors Nobumichi Tamura, senior scientist at the Advanced Light Source of the Lawrence Berkeley National Laboratory, Berkeley, California. Full article
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Article
Mechanical Performance of Concrete Exposed to Sewage—The Influence of Time and pH
Minerals 2021, 11(5), 544; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050544 - 20 May 2021
Viewed by 622
Abstract
Contact of concrete with aggressive factors, technological structures, reduces their durability through microstructural changes. This work presents the results of research on determining the influence of post grit chamber sewage and sewage from the active sludge chamber in three different environments, i.e., acidic, [...] Read more.
Contact of concrete with aggressive factors, technological structures, reduces their durability through microstructural changes. This work presents the results of research on determining the influence of post grit chamber sewage and sewage from the active sludge chamber in three different environments, i.e., acidic, neutral, and alkaline, on the structure and compressive strength of concrete. Compressive strength tests were carried out after 11.5 months of concrete cubes being submerged in the solutions and compared. To complete the studies, the photos of the microstructure were done. This made it possible to accentuate the relationship between the microstructure and performance characteristics of concrete. The time of storing the cubes in both acidic environments (sewage from post grit chamber and active sludge chamber) has a negative influence on their compressive strength. The compressive strength of cubes decreases along with the time. Compressive strength of cubes increases with increasing pH of the environment. Full article
(This article belongs to the Special Issue Application of Mineral-Based Amendments)
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Erratum
Erratum: Crespo et al. Ore Mineralogy, Trace Element Geochemistry and Geochronological Constraints at the Mollehuaca and San Juan de Chorunga Au-Ag Vein Deposits in the Nazca-Ocoña Metallogenic Belt, Arequipa, Peru. Minerals 2020, 10, 1112
Minerals 2021, 11(5), 543; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050543 - 20 May 2021
Viewed by 484
Abstract
In the published article [...] Full article
Article
Investigation on Dynamical Mechanics, Energy Dissipation, and Microstructural Characteristics of Cemented Tailings Backfill under SHPB Tests
Minerals 2021, 11(5), 542; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050542 - 19 May 2021
Viewed by 714
Abstract
As mining depth increases, the backfill mining method is more and more widely used in underground mines. The dynamic load generated by the blasting can affect the stability of the cemented tailings backfill (CTB). The CTB samples were prepared to conduct a test [...] Read more.
As mining depth increases, the backfill mining method is more and more widely used in underground mines. The dynamic load generated by the blasting can affect the stability of the cemented tailings backfill (CTB). The CTB samples were prepared to conduct a test of the split Hopkinson pressure bar (SHPB) to investigate the dynamic disturbance of CTB. The present paper discusses dynamical mechanics, energy dissipation, and microstructure analysis of CTB. Micro-computer tomography (micro-CT) scanning of CTB samples after the SHPB test was performed to analyze the evolution of internal cracks. The experimental results showed that when the average strain rate (ASR) increased from 30 to 98 s−1, the dynamic uniaxial compression strength (DUCS) of the CTB showed a trend of first increasing and decreasing with the increase in ASR. The dynamic stress–strain pre-peak curve of CTB directly enters the linear elastic stage. As ASR increases, the absorbed energy of the CTB shows a trend of first increasing and then decreasing. Moreover, according to the micro-CT scanning results, the crack area of CTB accounts for about 16% of the sample near the incident bar and about 1% near the transmitted bar. The crack area ratio is exponentially related to the specimen height. These findings can provide reasonable dynamical CTB strength data selection for underground pillar mining. Full article
(This article belongs to the Special Issue Backfilling Materials for Underground Mining, Volume II)
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Article
The Features of Native Gold in Ore-Bearing Breccias with Realgar-Orpiment Cement of the Vorontsovskoe Deposit (Northern Urals, Russia)
Minerals 2021, 11(5), 541; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050541 - 19 May 2021
Cited by 1 | Viewed by 671
Abstract
This paper describes native gold in ore-bearing breccias with realgar-orpiment cement from the Vorontsovskoe gold deposit (Northern Urals, Russia). Particular attention is paid to the morphological features of native gold and its relation to other minerals. The latter include both common (orpiment, barite, [...] Read more.
This paper describes native gold in ore-bearing breccias with realgar-orpiment cement from the Vorontsovskoe gold deposit (Northern Urals, Russia). Particular attention is paid to the morphological features of native gold and its relation to other minerals. The latter include both common (orpiment, barite, pyrite, prehnite, realgar) and rare species (Tl and Hg sulfosalts, such as boscardinite, dalnegroite, écrinsite, gillulyite, parapierrotite, routhierite, sicherite, vrbaite, etc.). The general geological and geochemical patterns of the Turyinsk-Auerbakh metallogenic province, including the presence of small non-economic copper porphyry deposits and general trend in change of the composition of native gold (an increase in the fineness of gold from high-temperature skarns to low-temperature realgar-orpiment breccias) confirm that the Vorontsovskoe deposit is an integral part of a large ore-magmatic system genetically associated with the formation of the Auerbakh intrusion. Full article
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Article
Ultramafic Alkaline Rocks of Kepino Cluster, Arkhangelsk, Russia: Different Evolution of Kimberlite Melts in Sills and Pipes
Minerals 2021, 11(5), 540; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050540 - 19 May 2021
Viewed by 623
Abstract
To provide new insights into the evolution of kimberlitic magmas, we have undertaken a detailed petrographic and mineralogical investigation of highly evolved carbonate–phlogopite-bearing kimberlites of the Kepino cluster, Arkhangelsk kimberlite province, Russia. The Kepino kimberlites are represented by volcanoclastic breccias and massive macrocrystic [...] Read more.
To provide new insights into the evolution of kimberlitic magmas, we have undertaken a detailed petrographic and mineralogical investigation of highly evolved carbonate–phlogopite-bearing kimberlites of the Kepino cluster, Arkhangelsk kimberlite province, Russia. The Kepino kimberlites are represented by volcanoclastic breccias and massive macrocrystic units within pipes as well as coherent porphyritic kimberlites within sills. The volcanoclastic units from pipes are similar in petrography and mineral composition to archetypal (Group 1) kimberlite, whereas the sills represent evolved kimberlites that exhibit a wide variation in amounts of carbonate and phlogopite. The late-stage evolution of kimberlitic melts involves increasing oxygen fugacity and fluid-phase evolution (forming carbonate segregations by exsolution, etc.). These processes are accompanied by the transformation of primary Al- and Ti-bearing phlogopite toward tetraferriphlogopite and the transition of spinel compositions from magmatic chromite to magnesian ulvöspinel and titanomagnetite. Similar primary kimberlitic melts emplaced as sills and pipes may be transitional to carbonatite melts in the shallow crust. The kimberlitic pipes are characterised by low carbonate amounts that may reflect the fluid degassing process during an explosive emplacement of the pipes. The Kepino kimberlite age, determined as 397.3 ± 1.2 Ma, indicates two episodes of ultramafic alkaline magmatism in the Arkhangelsk province, the first producing non-economic evolved kimberlites of the Kepino cluster and the second producing economic-grade diamondiferous kimberlites. Full article
(This article belongs to the Special Issue Petrogenesis and Geochemistry in Alkaline Ultramafic Rocks)
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Article
Chalcopyrite and Molybdenite Flotation in Seawater: The Use of Inorganic Dispersants to Reduce the Depressing Effects of Micas
Minerals 2021, 11(5), 539; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050539 - 19 May 2021
Cited by 2 | Viewed by 594
Abstract
The objective of this work was to study the effect of muscovite and biotite on the flotation of chalcopyrite and molybdenite in seawater, and the use of sodium hexametaphosphate and sodium silicate to improve copper and molybdenum recoveries. The impact of the inorganic [...] Read more.
The objective of this work was to study the effect of muscovite and biotite on the flotation of chalcopyrite and molybdenite in seawater, and the use of sodium hexametaphosphate and sodium silicate to improve copper and molybdenum recoveries. The impact of the inorganic dispersants on the settling properties of the resulting flotation tailings was also studied. It was found that muscovite and biotite depress the flotation of chalcopyrite and molybdenite in seawater, with this depressing effect being stronger at pH 11 than at pH 9. Sodium hexametaphosphate and sodium silicate increased the recoveries of copper and molybdenum in seawater. These dispersants render the mineral particles more negatively charged and remove the hydroxy-complexes of magnesium and calcium from the mineral particles causing dispersion of the slimes. The settling rates of the flotation tailings slightly decrease when sodium hexametaphosphate and sodium silicate were added in the flotation stage. The presence of ultrafine particles dispersed by the action of the inorganic dispersants negatively impacted the flocculation and sedimentation processes leading to high flocculant consumption, low settling rates and high turbidity of the supernatant. Full article
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Article
Growth Interruptions in Arctic Rhodoliths Correspond to Water Depth and Rhodolith Morphology
Minerals 2021, 11(5), 538; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050538 - 19 May 2021
Cited by 1 | Viewed by 644
Abstract
Coralline algae that form rhodoliths are widespread globally and their skeletal growth patterns have been used as (paleo-) environmental proxies in a variety of studies. However, growth interruptions (hiati) within their calcareous skeletons are regarded as problematic in this context. Here we investigated [...] Read more.
Coralline algae that form rhodoliths are widespread globally and their skeletal growth patterns have been used as (paleo-) environmental proxies in a variety of studies. However, growth interruptions (hiati) within their calcareous skeletons are regarded as problematic in this context. Here we investigated how hiati in the growth of Arctic rhodoliths from the Svalbard archipelago correspond to their environment and morphology. Using X-ray micro-computed tomography and stepwise model selections, we found that rhodoliths from deeper waters are subject to more frequent hiatus formation. In addition, rhodoliths with a higher sphericity (i.e., roundness) are less often affected by such growth interruptions. We conclude that these correlations are mainly regulated by hydrodynamics, because, in deeper waters, rhodoliths are not turned frequently enough to prevent a dieback of coralline algal thalli forming on the underside of the rhodolith. In this coherence, spheroidal rhodoliths are turned more easily, therefore shortening the amount of time between turnover events. Moreover, the incidence of light is more advantageous in shallower waters where rhodoliths exhibit a greater share of their surface to diffused ambient light, thus enabling thallus growth also on the down-facing surface of the rhodoliths. In consequence, information on the frequency of hiatus formation combined with rhodolith morphology might serve as a valuable proxy for (paleo-)environmental reconstructions in respect to light availability and the hydrodynamic regime. Full article
(This article belongs to the Special Issue Polar Marine Carbonates)
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Article
Long-Term Arsenic Sequestration in Biogenic Pyrite from Contaminated Groundwater: Insights from Field and Laboratory Studies
Minerals 2021, 11(5), 537; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050537 - 19 May 2021
Viewed by 677
Abstract
Pumping groundwater from arsenic (As)-contaminated aquifers exposes millions of people, especially those in developing countries, to high doses of the toxic contaminant. Previous studies have investigated cost-effective techniques to remove groundwater arsenic by stimulating sulfate-reducing bacteria (SRB) to form biogenic arsenian pyrite. This [...] Read more.
Pumping groundwater from arsenic (As)-contaminated aquifers exposes millions of people, especially those in developing countries, to high doses of the toxic contaminant. Previous studies have investigated cost-effective techniques to remove groundwater arsenic by stimulating sulfate-reducing bacteria (SRB) to form biogenic arsenian pyrite. This study intends to improve upon these past methods to demonstrate the effectiveness of SRB arsenic remediation at an industrial site in Florida. This study developed a ferrous sulfate and molasses mixture to sequester groundwater arsenic in arsenian pyrite over nine months. The optimal dosage of the remediating mixture consisted of 5 kg of ferrous sulfate, ~27 kg (60 lbs) of molasses, and ~1 kg (2 lbs) of fertilizer per 3785.4 L (1000 gallons) of water. The remediating mixture was injected into 11 wells hydrologically upgradient of the arsenic plume in an attempt to obtain full-scale remediation. Groundwater samples and precipitated biominerals were collected from June 2018 to March 2019. X-ray diffraction (XRD), X-ray fluorescence (XRF), electron microprobe (EMP), and scanning electron microscope (SEM) analyses determined that As has been sequestered mainly in the form of arsenian pyrite, which rapidly precipitated as euhedral crystals and spherical aggregates (framboids) 1–30 μm in diameter within two weeks of the injection. The analyses confirmed that the remediating mixture and injection scheme reduced As concentrations to near or below the site’s clean-up standard of 0.05 mg/L over the nine months. Moreover, the arsenian pyrite contained 0.03–0.89 weight percentage (wt%) of sequestered arsenic, with >80% of groundwater arsenic removed by SRB biomineralization. Considering these promising findings, the study is close to optimizing an affordable procedure for sequestrating dissolved As in industry settings. Full article
(This article belongs to the Special Issue Biogenic Metal Compounds for Hazardous Waste Remediation)
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Article
~25 Ma Ruby Mineralization in the Mogok Stone Tract, Myanmar: New Evidence from SIMS U–Pb Dating of Coexisting Titanite
Minerals 2021, 11(5), 536; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050536 - 19 May 2021
Cited by 1 | Viewed by 543
Abstract
Ruby (red corundum) is one of the most prominent colored gemstones in the world. The highest-quality ruby (“pigeon blood” ruby) comes from marbles of the Mogok Stone Tract in central Myanmar. Although Mogok ruby has been exploited since the 6th century AD, the [...] Read more.
Ruby (red corundum) is one of the most prominent colored gemstones in the world. The highest-quality ruby (“pigeon blood” ruby) comes from marbles of the Mogok Stone Tract in central Myanmar. Although Mogok ruby has been exploited since the 6th century AD, the formation time of this gemstone is ambiguous and controversial. In this paper, we describe a mineralogical, geochemical, and geochronological study of ruby and titanite in ruby-bearing marbles obtained from an outcrop in the Mogok Stone Tract, central Myanmar. Petrographic observations have shown that titanite generally occurs in the marble matrix or occurs as inclusions in ruby. These two types of titanite exhibit identical chemical compositions. In situ secondary ion mass spectrometer (SIMS) U–Pb dating of the separated titanite from two representative samples of ruby-bearing marbles yielded lower intercept ages of 25.15 ± 0.24 Ma (MSWD = 0.26) and 25.06 ± 0.22 Ma (MSWD = 0.15), respectively. Because the closure temperature of the U–Pb system in titanite is close to the temperature of ruby growth, the obtained U–Pb ages (~25 Ma) are suggested to represent the timing of the studied ruby formation in Mogok. The acquired ages are in agreement with the timing of post-collisional extension in the Himalaya related to the migration of the eastern Himalayan syntaxis. Combining our dating results with previous geochronological data from the Mogok Stone Tract, we suggest that the formation of the studied ruby is most likely related to the high-temperature metamorphic event in the marbles during the India–Asia collision. Our study not only confirms that texturally constrained titanite could be a precise geochronometer to date the mineralization of different types of ruby, but also provides important geochronological information linking gemstone formation to the India–Asia collision. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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Article
Mudrocks Lithofacies Characteristics and North-South Hydrocarbon Generation Difference of the Shahejie Formation in the Dongpu Sag
Minerals 2021, 11(5), 535; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050535 - 19 May 2021
Cited by 1 | Viewed by 496
Abstract
Lacustrine mudrocks are composed of minerals and organic matter (OM). The origin and preservation of OM are two controlling factors of the hydrocarbon generation capacity of mudrocks. It is a key method in source rock research to study the deposition process from the [...] Read more.
Lacustrine mudrocks are composed of minerals and organic matter (OM). The origin and preservation of OM are two controlling factors of the hydrocarbon generation capacity of mudrocks. It is a key method in source rock research to study the deposition process from the view of the OM and sedimentary environment. Following this idea, the reason for the discrepancy in hydrocarbon production between the northern and the southern part of Dongpu Sag is analyzed and discussed. The lacustrine mudrocks of the Shahejie Formation in Dongpu Sag are sampled and analyzed for information about mineralogy, microstructure, elemental geochemistry, and OM characteristics. The mudrocks are then divided into three lithofacies: silt-rich massive mudstone, homogeneous massive mudstone, and laminated mudstone. Each lithofacies shows distinct characteristics, and the hydrocarbon generation ability of them increases in sequence. Further discussion that the differences in hydrocarbon generation are caused by the sedimentary environment. The water depth, salinity, and reducibility of the sedimentary environments of these three lithofacies increase in sequence, as well. The correlation analysis indicates that it is the environment that controls the origin, accumulation, and preservation of OM in each lithofacies and then causes the great differences in hydrocarbon generation capacity. In Dongpu Sag, the proportion of laminated mudstone is much higher in the northern part, which leads to greater oil/gas production than the southern part. In research of source rocks, both the lithofacies characteristics and the sedimentary environments that control the characteristics should be studied. Full article
(This article belongs to the Special Issue Characterisation of Mudrocks: Textures and Mineralogy)
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Article
Simulation-Based Analysis of Hydrometallurgical Processes. Case Study: Small-Scale Gold Mining in Ecuador
Minerals 2021, 11(5), 534; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050534 - 19 May 2021
Viewed by 951
Abstract
In this work, two hydrometallurgical processes for gold recovery are explored for a small-scale gold mining case study located at Ponce Enriquez, Azuay, Ecuador. The hydrometallurgical systems consider the use of sodium cyanide and sodium thiosulfate as leaching agents, with and without the [...] Read more.
In this work, two hydrometallurgical processes for gold recovery are explored for a small-scale gold mining case study located at Ponce Enriquez, Azuay, Ecuador. The hydrometallurgical systems consider the use of sodium cyanide and sodium thiosulfate as leaching agents, with and without the incorporation of a subsystem for residual mercury removal. The proposed processes are modelled using the commercial simulator PRO/II interconnected with a Python scientific computing environment for performing stochastic simulations. Monte Carlo simulations, in which the conversion of the main units and the prices of gold vary following a random uniform distribution, permit observing the effects of these uncertainties on key recovery and economic indicators. The results facilitate the correlation between the inputs and outputs of interest as well as the visualization of the outputs variability for an adequate assessment of the systems under study by following a technical and social responsibility approach. Full article
(This article belongs to the Special Issue Hydrometallurgy in Gold Extraction)
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Review
Challenges Related to the Processing of Fines in the Recovery of Platinum Group Minerals (PGMs)
Minerals 2021, 11(5), 533; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050533 - 18 May 2021
Viewed by 705
Abstract
In order to increase the recovery of PGMs by flotation, it is necessary to optimise the liberation of the key minerals in which the platinum group elements (PGEs) are contained which include sulphides, arsenides, tellurides, and ferroalloys among others, while at the same [...] Read more.
In order to increase the recovery of PGMs by flotation, it is necessary to optimise the liberation of the key minerals in which the platinum group elements (PGEs) are contained which include sulphides, arsenides, tellurides, and ferroalloys among others, while at the same time ensuring the optimal depression of gangue minerals. In order to achieve this, comminution circuits usually consist of two or three stages of milling, in which the first stage is autogeneous, followed by ball milling. Further liberation is achieved in subsequent stages using ultra-fine grinding. Each comminution stage is followed by flotation in the so-called MF2 or MF3 circuits. While this staged process increases overall recoveries, overgrinding may occur, hence creating problems associated with fine particle flotation. This paper presents an overview of the mineralogy of most of the more significant PGM ores processed in South Africa and the various technologies used in comminution circuits. The paper then summarises the methodology used in flotation circuits to optimise recovery of fine particles in terms of the collectors, depressants, and frothers used. The effect of entrainment, slimes coating, changes in rheology caused by the presence of a significant amount of fines and of chromite recovery is addressed. Full article
(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)
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Article
Uranium Deposits of Erlian Basin (China): Role of Carbonaceous Debris Organic Matter and Hydrocarbon Fluids on Uranium Mineralization
Minerals 2021, 11(5), 532; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050532 - 18 May 2021
Cited by 1 | Viewed by 565
Abstract
The relationship of sedimentary organic matter, oil-gas and sandstone-type uranium (U) deposits is the key problem of U-mineralization. Whether migrate hydrocarbons participate in U-mineralization is still a controversy. Typical U deposits of the Erlian Basin in northeast China have been investigated through detailed [...] Read more.
The relationship of sedimentary organic matter, oil-gas and sandstone-type uranium (U) deposits is the key problem of U-mineralization. Whether migrate hydrocarbons participate in U-mineralization is still a controversy. Typical U deposits of the Erlian Basin in northeast China have been investigated through detailed petrography, mineralogical, micro spectroscopic, organic geochemical and C-isotope studies. Petrographic observations, Microscopic Laser Raman Spectroscopic, Infrared Spectroscopic and Scanning Electron Microscope analyses indicated there are three types of organic matter (including carbonaceous debris and migrated hydrocarbons). A significant amount of uranium was associated with pyrites, clay minerals and carbonaceous debris organic matter, either coexisted with hydrocarbon fluids. There are at least two stages mineralization events, stage I is related to sedimentary organic matter (syngenetic pre-enrichment stage), and stage II is related to mobile hydrocarbon fluids (main mineralization stage). Therefore, our results support that migrated hydrocarbons were involved as a reducing agent for the main uranium mineralization after synsedimentary mineralization. Full article
(This article belongs to the Special Issue Geology of Uranium Deposits)
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Article
Occurrence and Distribution of Moganite and Opal-CT in Agates from Paleocene/Eocene Tuffs, El Picado (Cuba)
Minerals 2021, 11(5), 531; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050531 - 18 May 2021
Cited by 1 | Viewed by 700
Abstract
Agates in Paleocene/Eocene tuffs from El Picado/Los Indios, Cuba were investigated to characterize the mineral composition of the agates and to provide data for the reconstruction of agate forming processes. The volcanic host rocks are strongly altered and fractured and contain numerous fissures [...] Read more.
Agates in Paleocene/Eocene tuffs from El Picado/Los Indios, Cuba were investigated to characterize the mineral composition of the agates and to provide data for the reconstruction of agate forming processes. The volcanic host rocks are strongly altered and fractured and contain numerous fissures and veins mineralized by quartz and chalcedony. These features indicate secondary alteration and silicification processes during tectonic activities that may have also resulted in the formation of massive agates. Local accumulation of manganese oxides/hydroxides, as well as uranium (uranyl-silicate complexes), in the agates confirm their contemporaneous supply with SiO2 and the origin of the silica-bearing solutions from the alteration processes. The mineral composition of the agates is characterized by abnormal high bulk contents of opal-CT (>6 wt%) and moganite (>16 wt%) besides alpha-quartz. The presence of these elevated amounts of “immature” silica phases emphasize that agate formation runs through several structural states of SiO2 with amorphous silica as the first solid phase. A remarkable feature of the agates is a heterogeneous distribution of moganite within the silica matrix revealed by micro-Raman mapping. The intensity ratio of the main symmetric stretching-bending vibrations (A1 modes) of alpha-quartz at 465 cm−1 and moganite at 502 cm−1, respectively, was used to depict the abundance of moganite in the silica matrix. The zoned distribution of moganite and variations in the microtexture and porosity of the agates indicate a multi-phase deposition of SiO2 under varying physico-chemical conditions and a discontinuous silica supply. Full article
(This article belongs to the Special Issue Agates: Types, Mineralogy, Deposits, Host Rocks, Ages and Genesis)
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Article
Geochemical and Petrographic Characterization of Bricks and Mortars of the Parish Church SANTA Maria in Padovetere (Comacchio, Ferrara, Italy)
Minerals 2021, 11(5), 530; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050530 - 18 May 2021
Cited by 2 | Viewed by 702
Abstract
From the 1950s and 1960s of the last century, a parish church dating back to the 6th century AD was identified during reclamation works of Valle Pega. The archaeological investigation allowed the recovery of the parish and the attached baptistery, as well as [...] Read more.
From the 1950s and 1960s of the last century, a parish church dating back to the 6th century AD was identified during reclamation works of Valle Pega. The archaeological investigation allowed the recovery of the parish and the attached baptistery, as well as some tombs closely connected to the church. Following the excavation, it was possible to collect some samples of bricks and mortars in order to identify the different compositions of the materials used for the construction of the parish. All the samples were analyzed through optical microscopy, X-ray powder diffractometric analysis and observation through scanning electron microscope. Thanks to the investigations carried out on the samples, it was possible to hypothesize the different construction phases and the different materials used and to identify the firing temperatures at which the bricks were built. Full article
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Article
Recovery of Iron from Mill Scale by Reduction with Carbon Monoxide
Minerals 2021, 11(5), 529; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050529 - 17 May 2021
Viewed by 666
Abstract
The mill scale is a waste from the iron and steel industry. Due to the high content of iron in the form of oxides, it is an attractive material for the recovery of metallic iron by reduction. The product of mill scale reduction [...] Read more.
The mill scale is a waste from the iron and steel industry. Due to the high content of iron in the form of oxides, it is an attractive material for the recovery of metallic iron by reduction. The product of mill scale reduction is an iron with a very extended surface and a high affinity for oxygen. The smaller iron particles are, the easier it is for spontaneous rapid oxidation, which can be linked to pyrophoricity. This article presents results of experiments using the TG/DTA thermal analysis method aimed at verifying the possibility of recovering iron from the mill scale by a reduction with carbon monoxide at 850 °C, 950 °C, and 1050 °C, taking into account the phenomenon of secondary oxidation in contact with oxygen from air at temperatures of 300 °C, 350 °C, and 400 °C. Two forms of mill scale were used for tests, in the original state and after grinding to develop the surface. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Insights into Selection of the Auxiliary Collector and Its Applicability Analysis for Improving Molybdenite Flotation
Minerals 2021, 11(5), 528; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050528 - 17 May 2021
Viewed by 536
Abstract
In this study, two auxiliary collectors (methyl naphthalene and naphthalene) of molybdenite and the traditional collector (kerosene) were mixed for molybdenite flotation, respectively. According to the selection and analysis of the auxiliary collector, it was found that the surface energy ( [...] Read more.
In this study, two auxiliary collectors (methyl naphthalene and naphthalene) of molybdenite and the traditional collector (kerosene) were mixed for molybdenite flotation, respectively. According to the selection and analysis of the auxiliary collector, it was found that the surface energy (γC= 44.50 mJ/m2) of the polycyclic aromatic hydrocarbons is very close to that (γS= 42.55 mJ/m2) of the molybdenite {100} surface. Therefore, it can be physically adsorbed onto the molybdenite {100} surface according to the principle of similar compatibility. Batch flotation was conducted on actual ore with the mixed collector, compared with kerosene alone. Batch flotation results showed that the mixed collector at a mass ratio of 95:5 of main collector to auxiliary collector at pH 11.0 improved molybdenite flotation, that is, the Mo recovery was increased by 3–4%. The practical application feasibility of the auxiliary collector was analyzed by the filtration speed of the flotation concentrate and the crystal resolution characteristics of the auxiliary collector. The results show that solid naphthalene (Nap) is easy to crystallize at low temperature and adhere to the surface of the flotation concentrate, resulting in a decrease of filtration velocity, while liquid methylnaphthalene (MNap) does not crystallize at low temperature. These results imply that the mixed collector Kerosene/MNap can generate a superior synergistic effect and achieve better collecting capacity than kerosene alone, resulting in the increase of flotation recovery by 3–4 percentage points. Moreover, the addition of MNap has little negative impact on the subsequent treatment of the product. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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Article
Geochronological and Paleomagnetic Constraints on the Lower Cretaceous Dalazi Formation from the Yanji Basin, NE China, and its Tectonic Implication
Minerals 2021, 11(5), 527; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050527 - 17 May 2021
Cited by 1 | Viewed by 591
Abstract
The Lower Cretaceous Dalazi Formation in the Yanji Basin, eastern Jilin Province is of particular interest because it contains key fresh water fossil taxa, oil and gas resources, a potential terrestrial Albian–Cenomanian boundary, and regional unconformities. However, the lack of a precise chronology [...] Read more.
The Lower Cretaceous Dalazi Formation in the Yanji Basin, eastern Jilin Province is of particular interest because it contains key fresh water fossil taxa, oil and gas resources, a potential terrestrial Albian–Cenomanian boundary, and regional unconformities. However, the lack of a precise chronology for the non-marine strata has precluded a better understanding of the regional stratigraphic correlation and terrestrial processes. Here, we report magnetostratigraphic and U–Pb geochronologic results of a sedimentary sequence from the Xing’antun section in the Yanji Basin. Thirty-two zircons from the tuff sample were analyzed by secondary ion mass spectrometry (SIMS); the U–Pb zircon dating method yielded a weighted mean of 206Pb/238U age of 105.7 ± 0.8 Ma (2σ, internal error). Paleomagnetic results show that the Dalazi Formation is of normal polarity, which was correlated to the early chron C34n constrained by the SIMS U–Pb zircon geochronologic data, further demonstrating that the terrestrial sedimentary sequence of the upper Dalazi Formation is of late Albian age. The established geochronologic framework allows the regional correlation of the Dalazi Formation in the Yanji Basin to the strata from other terrestrial sequences in northeastern China. The similar geodynamic and geologic background between the Yanji Basin and other terrestrial rift basins in northeastern China suggests that the unconformity between the Dalazi and Longjing formations may represent syn-rift and post-rift stages in the Yanji Basin, and thus the switch from extension to contraction during the mid-Cretaceous, precisely constrained to ~106–101 Ma based on our new chronology and previously published high-precision U–Pb dating of the lower Longjing Formation. It is most likely attributable to the docking of the west Pacific plate along the East Asian continental margin. Full article
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Editorial
Editorial for Special Issue “Microtexture Characterization of Rocks and Minerals”
Minerals 2021, 11(5), 526; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050526 - 17 May 2021
Viewed by 441
Abstract
Microtextures, the physical or structural aspects of minerals and rocks, may include the interrelationships of minerals, the preferred orientation of grains, the internal textures of minerals, etc [...] Full article
(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)
Review
Asbestiform Amphiboles and Cleavage Fragments Analogues: Overview of Critical Dimensions, Aspect Ratios, Exposure and Health Effects
Minerals 2021, 11(5), 525; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050525 - 16 May 2021
Cited by 2 | Viewed by 605
Abstract
The term asbestos refers to a group of serpentine (chrysotile) and amphibole (amosite, crocidolite, anthophyllite, tremolite and actinolite) minerals with a fibrous habit. Their chemical-physical properties make them one of the most important inorganic materials for industrial purposes and technological applications. However, the [...] Read more.
The term asbestos refers to a group of serpentine (chrysotile) and amphibole (amosite, crocidolite, anthophyllite, tremolite and actinolite) minerals with a fibrous habit. Their chemical-physical properties make them one of the most important inorganic materials for industrial purposes and technological applications. However, the extraction, use and marketing of these minerals have been prohibited due to proven harmful effects, mainly involving the respiratory system. In addition to the known six minerals classified as asbestos, the natural amphiboles and serpentine polymorphs antigorite and lizardite, despite having the same composition of asbestos, do not have the same morphology. These minerals develop chemical and geometric (length > 5 μm, width < 3 μm and length: diameter > 3:1), but not morphological, analogies with asbestos, which is regulated by the WHO. The debate about their potential hazardous properties is open and ongoing; therefore, their morphological characterization has a key role in establishing a reliable asbestos hazard scenario. This review focuses on evaluating the most relevant papers, evidencing the need for a reappraisal. Different in vitro, in vivo and epidemiological studies report information about cleavage fragments with critical dimensions similar to asbestos fibres, but very few works target fragments below 5 µm in length. Breathable smaller fibres could have deleterious effects on human health and cannot be disregarded from the risk assessment process. Furthermore, a few studies suggest that the carcinogenic nature of short fibres is not excluded. This review highlights that it is worth investigating the effects of this size range of elongated mineral particles and fibres. Full article
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Article
Digital Twins with Distributed Particle Simulation for Mine-to-Mill Material Tracking
Minerals 2021, 11(5), 524; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050524 - 15 May 2021
Viewed by 858
Abstract
Systems for transport and processing of granular media are challenging to analyse, operate and optimise. In the mining and mineral processing industries, these systems are chains of processes with a complex interplay among the equipment, control and processed material. The material properties have [...] Read more.
Systems for transport and processing of granular media are challenging to analyse, operate and optimise. In the mining and mineral processing industries, these systems are chains of processes with a complex interplay among the equipment, control and processed material. The material properties have natural variations that are usually only known at certain locations. Therefore, we explored a material-oriented approach to digital twins with a particle representation of the granular media. In digital form, the material is treated as pseudo-particles, each representing a large collection of real particles of various sizes, shapes and mineral properties. Movements and changes in the state of the material are determined by the combined data from control systems, sensors, vehicle telematics and simulation models at locations where no real sensors could see. The particle-based representation enables material tracking along the chain of processes. Each digital particle can act as a carrier of observational data generated by the equipment as it interacts with the real material. This make it possible to better learn the material properties from process observations and to predict the effect on downstream processes. We tested the technique on a mining simulator and demonstrated the analysis that can be performed using data from cross-system material tracking. Full article
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Article
Low Temperature Illitization through Illite-Dioctahedral Vermiculite Mixed Layers in a Tropical Saline Lake Rich in Hydrothermal Fluids (Sochagota Lake, Colombia)
Minerals 2021, 11(5), 523; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050523 - 15 May 2021
Viewed by 722
Abstract
In this investigation, we showed that high salinity promoted by hydrothermal inputs, reducing conditions of sediments with high content in organic matter, and the occurrence of an appropriate clay mineral precursor provide a suitable framework for low-temperature illitization processes. We studied the sedimentary [...] Read more.
In this investigation, we showed that high salinity promoted by hydrothermal inputs, reducing conditions of sediments with high content in organic matter, and the occurrence of an appropriate clay mineral precursor provide a suitable framework for low-temperature illitization processes. We studied the sedimentary illitization process that occurs in carbonaceous sediments from a lake with saline waters (Sochagota Lake, Colombia) located at a tropical latitude. Water isotopic composition suggests that high salinity was produced by hydrothermal contribution. Materials accumulated in the Sochagota Lake’s southern entrance are organic matter-poor sediments that contain detrital kaolinite and quartz. On the other hand, materials formed at the central segment and near the lake exit (north portion) are enriched in organic matter and characterized by the crystallization of Fe-sulfides. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and energy dispersive X-ray spectrometry (EDX) data allowed for the identification of illite and illite-dioctahedral vermiculite mixed layers (I-DV), which are absent in the southern sediments. High humidity and temperate climate caused the formation of small-sized metastable intermediates of I-DV particles by the weathering of the source rocks in the Sochagota Lake Basin. These particles were deposited in the low-energy lake environments (middle and north part). The interaction of these sediments enriched in organic matter with the saline waters of the lake enriched in hydrothermal K caused a reducing environment that favored Fe mobilization processes and its incorporation to I-DV mixed layers that acted as mineral precursor for fast low temperature illitization, revealing that in geothermal areas clays in lakes favor a hydrothermal K uptake. Full article
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Article
Taloe—Sedimentation in an Intermittent Lake (Russian Federation, Republic of Khakassia)
Minerals 2021, 11(5), 522; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050522 - 14 May 2021
Cited by 1 | Viewed by 552
Abstract
This paper examines the mineral and geochemical features of lake sediments and waters in intermittent Lake Taloe, located in a semiarid climate. Minerals that belong to groups of oxides, sulfides, aluminosilicates, carbonates, sulfates, and halides are identified through the use of precision methods. [...] Read more.
This paper examines the mineral and geochemical features of lake sediments and waters in intermittent Lake Taloe, located in a semiarid climate. Minerals that belong to groups of oxides, sulfides, aluminosilicates, carbonates, sulfates, and halides are identified through the use of precision methods. The resulting mineral species are divided by genetic features into two associations: terrigenous and hydrogenic. The terrigenous association includes water-insoluble minerals, while the hydrogenic association combines typical hydrogenic minerals. The regularities of the accumulation and distribution of minerals along the lake laterally and to a depth of up to one meter are also examined. The order of deposition of hydrogenous association minerals from sulfate-chloride lake waters was established. The obtained results are confirmed and supplemented by physicochemical calculations, which show the equilibrium of lake waters with hydroxides, oxides, aluminosilicates, carbonates, and sulfates. It has been established that the formation of minerals mainly occurs through evaporative concentration in conjunction with bedrock weathering. Full article
(This article belongs to the Special Issue Mineralogy, Petrology and Geochemistry of Evaporites)
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Review
The Surface-Vacancy Model—A General Theory of the Dissolution of Minerals and Salts
Minerals 2021, 11(5), 521; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050521 - 14 May 2021
Viewed by 534
Abstract
The kinetics of the dissolution of salts and minerals remains a field of active research because these reactions are important to many fields, such as geochemistry, extractive metallurgy, corrosion, biomaterials, dentistry, and dietary uptake. A novel model, referred to as the surface-vacancy model, [...] Read more.
The kinetics of the dissolution of salts and minerals remains a field of active research because these reactions are important to many fields, such as geochemistry, extractive metallurgy, corrosion, biomaterials, dentistry, and dietary uptake. A novel model, referred to as the surface-vacancy model, has been proposed by the author as a general mechanism for the primary events in dissolution. This paper expands on the underlying physical model while serving as an update on current progress with the application of the model. This underlying physical model envisages that cations and anions depart separately from the surface leaving a surface vacancy of charge opposite to that of the departing ion on the surface. This results in an excess surface charge, which in turn affects the rate of departing ions. Thus, a feedback mechanism is established in which the departing of ions creates excess surface charge, and this net surface charge, in turn, affects the rate of departure. This model accounts for the orders of reaction, the equilibrium conditions, the acceleration or deceleration of rate in the initial phase and the surface charge. The surface-vacancy model can also account for the effect of impurities in the solution, while it predicts phenomena, such as ‘partial equilibrium’, that are not contemplated by other models. The underlying physical model can be independently verified, for example, by measurements of the surface charge. This underlying physical model has implications for fields beyond dissolution studies. Full article
(This article belongs to the Special Issue Mineral Dissolution and Growth Kinetics)
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Article
U-Pb Age Dating and Geochemistry of Soft-Sediment Deformation Structure-Bearing Late Cretaceous Volcano-Sedimentary Basins in the SW Korean Peninsula and Their Tectonic Implications
Minerals 2021, 11(5), 520; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050520 - 14 May 2021
Viewed by 531
Abstract
Cretaceous volcano-sedimentary basins and successions in the Korean Peninsula are located along NE-SW- and NNE-SSW-trending sinistral strike–slip fault systems. Soft-sediment deformation structures (SSDS) of lacustrine sedimentary strata occur in the Wido, Buan, and Haenam areas of the southwestern Korean Peninsula. In this study, [...] Read more.
Cretaceous volcano-sedimentary basins and successions in the Korean Peninsula are located along NE-SW- and NNE-SSW-trending sinistral strike–slip fault systems. Soft-sediment deformation structures (SSDS) of lacustrine sedimentary strata occur in the Wido, Buan, and Haenam areas of the southwestern Korean Peninsula. In this study, systematic geological, geochronological, and geochemical investigations of the volcanic-sedimentary successions were conducted to constrain the origin and timing of SSDS-bearing lacustrine strata. The SSDS-bearing strata is conformably underlain and overlain by volcanic rocks, and it contains much volcaniclastic sediment and is interbedded with tuffs. The studied SSDSs were interpreted to have formed by ground shaking during syndepositional earthquakes. U-Pb zircon ages of volcanic and volcaniclastic rocks within the studied volcano-sedimentary successions were ca. 87–84 Ma, indicating that active volcanism was concurrent with lacustrine sedimentation. Geochemical characteristics indicate that these mostly rhyolitic rocks are similar to subduction-related calc-alkaline volcanic rocks from an active continental margin. This suggests that the SSDSs in the study area were formed by earthquakes related to proximal volcanic activity due to the oblique subduction of the Paleo-Pacific Plate during the Late Cretaceous. Full article
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Article
X-ray Total Scattering Study of Phases Formed from Cement Phases Carbonation
Minerals 2021, 11(5), 519; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050519 - 14 May 2021
Viewed by 610
Abstract
Carbonation in cement binders has to be thoroughly understood because it affects phase assemblage, binder microstructure and durability performance of concretes. This is still not the case as the reaction products can be crystalline, nanocrystalline and amorphous. The characterisation of the last two [...] Read more.
Carbonation in cement binders has to be thoroughly understood because it affects phase assemblage, binder microstructure and durability performance of concretes. This is still not the case as the reaction products can be crystalline, nanocrystalline and amorphous. The characterisation of the last two types of components are quite challenging. Here, carbonation reactions have been studied in alite-, belite- and ye’elimite-containing pastes, in controlled conditions (3% CO2 and RH = 65%). Pair distribution function (PDF) jointly with Rietveld and thermal analyses have been applied to prove that ettringite decomposed to yield crystalline aragonite, bassanite and nano-gibbsite without any formation of amorphous calcium carbonate. The particle size of gibbsite under these conditions was found to be larger (~5 nm) than that coming from the direct hydration of ye’elimite with anhydrite (~3 nm). Moreover, the carbonation of mixtures of C-S-H gel and portlandite, from alite and belite hydration, led to the formation of the three crystalline CaCO3 polymorphs (calcite, aragonite and vaterite), amorphous silica gel and amorphous calcium carbonate. In addition to their PDF profiles, the thermal analyses traces are thoroughly analysed and discussed. Full article
(This article belongs to the Special Issue Cement Related Minerals)
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Article
Use of Natural Clinoptilolite in the Preparation of an Efficient Adsorbent for Ciprofloxacin Removal from Aqueous Media
Minerals 2021, 11(5), 518; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050518 - 14 May 2021
Cited by 1 | Viewed by 689
Abstract
The adsorption of the antibiotic ciprofloxacin (CIP) from an aqueous solution by natural zeolite, the calcium-rich clinoptilolite (CLI), and magnetite-coated CLI (MAG-CLI) was investigated. Both CLI and MAG-CLI showed a high adsorption affinity towards CIP at 283, 288 and 293 K at a [...] Read more.
The adsorption of the antibiotic ciprofloxacin (CIP) from an aqueous solution by natural zeolite, the calcium-rich clinoptilolite (CLI), and magnetite-coated CLI (MAG-CLI) was investigated. Both CLI and MAG-CLI showed a high adsorption affinity towards CIP at 283, 288 and 293 K at a pH of 5. Adsorption kinetics studied for the initial concentrations of 15–75 mg CIP dm−3 follow Lagergren’s pseudo-second order equation and the adsorption is best represented by the Langmuir model. The adsorption mechanism involves strong electrostatic interactions between negatively charged aluminosilicate lattice and the cationic form of CIP accompanied by an ion-exchange reaction. Magnetite coverage (approx. 12 wt.%) induces magnetism, which can facilitate the separation process. The coverage does not influence the adsorption activity of CLI. The leaching test showed that the MAG coating protects the adsorbent from CIP leaching. This is ascribed to interactions between the CIP carboxyl groups and magnetite nano-particles. Antibacterial tests showed strong antibacterial activity of the ciprofloxacin-containing adsorbents towards pathogenic E. coli and S. aureus. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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