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Volume 8
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Minerals, Volume 8, Issue 7 (July 2018) – 48 articles

Cover Story (view full-size image): We have established that spatial distribution of content, morphology, grain size, composition, crystal structure and alteration in rock formation and most accessory minerals within the Kovdor phoscorite–carbonatite pipes, reflect the gradual decrease of crystallization temperature and oxygen fugacity from the pipe margin toward its axis. We believe that 3D mineralogical mapping is the best way to reconstruct genesis of any geological complex and to construct its geometallulgical model. Further, this approach helped predict localities of rare secondary minerals and discover some new minerals. View this paper
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25 pages, 4052 KiB  
Article
Variographic Assessment of Total Process Measurement System Performance for a Complete Ore-to-Shipping Value Chain
by Karin Engström and Kim H. Esbensen
Minerals 2018, 8(7), 310; https://doi.org/10.3390/min8070310 - 23 Jul 2018
Cited by 4 | Viewed by 4398
Abstract
Variographic characterisation has been shown to be a powerful tool to assess the performance of process measurement systems, using existing process data. Variogram interpretation enables decomposition of variabilities stemming from the process and measurement system, respectively, allowing to determine if measurements are able [...] Read more.
Variographic characterisation has been shown to be a powerful tool to assess the performance of process measurement systems, using existing process data. Variogram interpretation enables decomposition of variabilities stemming from the process and measurement system, respectively, allowing to determine if measurements are able to describe the true process variability with sufficient resolution. This study evaluated 14 critical sampling locations, covering a total of 34 separate measurement systems, along the full processing value chain at Luossavaara Kiirunavaara limited company (LKAB), Sweden. A majority of the variograms show low sill levels, indicating that many sub-processes are well controlled. Many also show low nugget effect, indicating satisfactory measurement systems. However, some notable exceptions were observed, pointing to systems in the need of improvement. Even if some of these were previously recognized internally at LKAB, the use of variographic characterisation provide objective and numerical evidence of measurement system performance. The study also showed some unexpected results, for example that slurry shark-fin and spear sampling show acceptable variogram characteristics for the present materials, despite the associated incorrect sampling errors. On the other hand, the results support previous conclusions indicating that manual sampling and cross belt hammer samplers are leading to unacceptably large sampling errors and should be abandoned. Such specific findings underline the strength of comprehensive empirical studies. Based on the present compilation of results, it is possible to conduct rational enquiry of all evaluated measurement systems, enabling objective prioritization of where improvement efforts will have the largest cost–benefit effect. Full article
(This article belongs to the Special Issue Sampling Across the Mine Value Chain)
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16 pages, 5199 KiB  
Article
Determination of Dissolution Rates of Ag Contained in Metallurgical and Mining Residues in the S2O32−-O2-Cu2+ System: Kinetic Analysis
by Julio C. Juárez Tapia, Francisco Patiño Cardona, Antonio Roca Vallmajor, Aislinn M. Teja Ruiz, Iván A. Reyes Domínguez, Martín Reyes Pérez, Miguel Pérez Labra and Mizraim U. Flores Guerrero
Minerals 2018, 8(7), 309; https://doi.org/10.3390/min8070309 - 23 Jul 2018
Cited by 8 | Viewed by 3620
Abstract
The materials used to conduct kinetic study on the leaching of silver in the S2O32−-O2-Cu2+ system were mining residues (tailings) from the Dos Carlos site in the State of Hidalgo, Mexico, which have an estimated [...] Read more.
The materials used to conduct kinetic study on the leaching of silver in the S2O32−-O2-Cu2+ system were mining residues (tailings) from the Dos Carlos site in the State of Hidalgo, Mexico, which have an estimated concentration of Ag = 71 g∙ton−1. The kinetic study presented in this paper assessed the effects of the following variables on Ag dissolution rate: particle diameter (d0), temperature (T), copper concentration [Cu2+], thiosulfate concentration [S2O32−], pH, [OH−], stirring rate (RPM), and partial pressure of oxygen (PO2). Temperature has a favorable effect on the leaching rate of Ag, obtaining an activation energy (Ea) = 43.5 kJ∙mol−1 in a range between 288 K (15 °C) and 328 K (55 °C), which indicates that the dissolution reaction is controlled by the chemical reaction. With a reaction order of n = 0.4, the addition of [Cu2+] had a catalytic effect on the leaching rate of silver, as opposed to not adding it. The dissolution rate is dependent on [S2O32−] in a range between 0.02 mol·L−1 and 0.06 mol·L−1. Under the studied conditions, variables d0, [OH−] and RPM did not have an effect on the overall rate of silver leaching. Full article
(This article belongs to the Special Issue Modeling, Design and Optimization of Multiphase Systems in Minerals Processing)
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24 pages, 6221 KiB  
Article
Sharyginite, Ca3TiFe2O8, A New Mineral from the Bellerberg Volcano, Germany
by Rafał Juroszek, Hannes Krüger, Irina Galuskina, Biljana Krüger, Lidia Jeżak, Bernd Ternes, Justyna Wojdyla, Tomasz Krzykawski, Leonid Pautov and Evgeny Galuskin
Minerals 2018, 8(7), 308; https://doi.org/10.3390/min8070308 - 21 Jul 2018
Cited by 10 | Viewed by 4983
Abstract
The new mineral sharyginite, Ca3TiFe2O8 (P21ma, Z = 2, a = 5.423(2) Å, b = 11.150(8) Å, c = 5.528(2) Å, V = 334.3(3) Å3), a member of the anion deficient [...] Read more.
The new mineral sharyginite, Ca3TiFe2O8 (P21ma, Z = 2, a = 5.423(2) Å, b = 11.150(8) Å, c = 5.528(2) Å, V = 334.3(3) Å3), a member of the anion deficient perovskite group, was discovered in metacarbonate xenoliths in alkali basalt from the Caspar quarry, Bellerberg volcano, Eifel, Germany. In the holotype specimen, sharyginite is widespread in the contact zone of xenolith with alkali basalt. Sharyginite is associated with fluorellestadite, cuspidine, brownmillerite, rondorfite, larnite and minerals of the chlormayenite-wadalite series. The mineral usually forms flat crystals up to 100 µm in length, which are formed by pinacoids {100}, {010} and {001}. Crystals are flattened on (010). Sharyginite is dark brown, opaque with a brown streak and has a sub-metallic lustre. In reflected light, it is light grey and exhibits rare yellowish-brown internal reflections. The calculated density of sharyginite is 3.943 g·cm-3. The empirical formula calculated on the basis of 8 O apfu is Ca3.00(Fe3+1.00Ti4+0.86Mn4+0.11Zr0.01Cr3+0.01Mg0.01)Σ2(Fe3+0.76Al0.20Si0.04)Σ1.00O8. The crystal structure of sharyginite, closely related to shulamitite Ca3TiFeAlO8 structure, consists of double layers of corner-sharing (Ti, Fe3+) O6 octahedra, which are separated by single layers of (Fe3+O4) tetrahedra. We suggest that sharyginite formed after perovskite at high-temperature conditions >1000°C. Full article
(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)
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3 pages, 164 KiB  
Editorial
Editorial for Special Issue “Fluid Inclusions: Study Methods, Applications, and Case Histories”
by Martin Feely
Minerals 2018, 8(7), 307; https://doi.org/10.3390/min8070307 - 21 Jul 2018
Cited by 1 | Viewed by 2274
Abstract
The pioneering work of H.C. Sorby [1] in the mid-19th century highlighted the scientific importance of fluid inclusions in minerals [...] Full article
(This article belongs to the Special Issue Fluid Inclusions: Study Methods, Applications and Case Histories)
18 pages, 5703 KiB  
Article
Physicochemical Model of Formation of Gold-Bearing Magnetite-Chlorite-Carbonate Rocks at the Karabash Ultramafic Massif (Southern Urals, Russia)
by Valery Murzin, Konstantin Chudnenko, Galina Palyanova, Aleksandr Kissin and Dmitry Varlamov
Minerals 2018, 8(7), 306; https://doi.org/10.3390/min8070306 - 20 Jul 2018
Cited by 6 | Viewed by 4991
Abstract
We present a physicochemical model for the formation of magnetite-chlorite-carbonate rocks with copper gold in the Karabash ultramafic massif in the Southern Urals, Russia. The model was constructed based on the formation geotectonics of the Karabash massif, features of spatial distribution of metasomatically [...] Read more.
We present a physicochemical model for the formation of magnetite-chlorite-carbonate rocks with copper gold in the Karabash ultramafic massif in the Southern Urals, Russia. The model was constructed based on the formation geotectonics of the Karabash massif, features of spatial distribution of metasomatically altered rocks in their central part, geochemical characteristics and mineral composition of altered ultramafic rocks, data on the pressure and temperature conditions of formation, and composition of the ore-forming fluids. Magnetite-chlorite-carbonate rocks were formed by the hydrothermal filling of the free space, whereas chloritolites were formed by the metasomatism of the serpentinites. As the source of the petrogenic and ore components, we considered rocks (serpentinites, gabbro, and limestones), deep magmatogenic fluids, probably mixed with metamorphogenic fluids released during dehydration and deserpentinization of rocks in the lower crust, and meteoric waters. The model supports the involvement of sodium chloride-carbon dioxide fluids extracting ore components (Au, Ag, and Cu) from deep-seated rocks and characterized by the ratio of ore elements corresponding to Clarke values in ultramafic rocks. The model calculations show that copper gold can also be deposited during serpentinization of deep-seated olivine-rich rocks and ore fluids raised by the tectonic flow to a higher hypsometric level. The results of our research allow predicting copper gold-rich ore occurrences in ultramafic massifs. Full article
(This article belongs to the Special Issue Experimental and Thermodynamical Modeling of Ore-Forming Processes in Magmatic and Hydrothermal Systems)
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16 pages, 548 KiB  
Article
What the Diffuse Layer (DL) Reveals in Non-Linear SFG Spectroscopy
by Simone Pezzotti, Daria Ruth Galimberti, Y. Ron Shen and Marie-Pierre Gaigeot
Minerals 2018, 8(7), 305; https://doi.org/10.3390/min8070305 - 20 Jul 2018
Cited by 29 | Viewed by 4710
Abstract
Following our recent work [Phys. Chem. Chem. Phys. 20:5190–99 (2018)] that provided the means to unambigously define and extract the three water regions at any charged interface (solid–liquid and air–liquid alike), denoted the BIL (Binding Interfacial Layer), DL (Diffuse Layer) and Bulk, and [...] Read more.
Following our recent work [Phys. Chem. Chem. Phys. 20:5190–99 (2018)] that provided the means to unambigously define and extract the three water regions at any charged interface (solid–liquid and air–liquid alike), denoted the BIL (Binding Interfacial Layer), DL (Diffuse Layer) and Bulk, and how to calculate their associated non-linear Sum Frequency Generation Spectroscopy (SFG) χ2(ω) spectroscopic contributions from Density Functional Theory (DFT)-based ab initio molecular dynamics simulations (DFT-MD/AIMD), we show here that the χDL2(ω) signal arising from the DL water region carries a wealth of essential information on the microscopic and macroscopic properties of interfaces. We show that the χDL2(ω) signal carries information on the surface potential and surface charge, the isoelectric point, EDL (Electric Double Layer) formation, and the relationship between a nominal electrolyte solution pH and surface hydroxylation state. This work is based on DFT-MD/AIMD simulations on a (0001) α–quartz–water interface and on the air–water interface, with various surface quartz hydroxylation states and various electrolyte concentrations. The conclusions drawn make use of the interplay between experiments and simulations. Most of the properties listed above can now be extracted from experimental χDL2(ω) alone with the protocols given in this work, or by making use of the interplay between experiments and simulations, as described in this work. Full article
(This article belongs to the Special Issue Molecular Simulation of Mineral-Solution Interfaces)
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12 pages, 11248 KiB  
Article
Interaction Mechanism between Molybdenite and Kaolinite in Gypsum Solution Using Kerosene as the Flotation Collector
by Liqing Sun, Yijun Cao, Yinfei Liao and Zilong Ma
Minerals 2018, 8(7), 304; https://doi.org/10.3390/min8070304 - 20 Jul 2018
Cited by 5 | Viewed by 3347
Abstract
This paper aims to understand the fundamental interaction mechanism between molybdenite and kaolinite in gypsum solution using kerosene as collector. Micro-flotation tests were conducted to study the effect of gypsum solution on the flotation performance of mixed −74 μm molybdenite and −10 μm [...] Read more.
This paper aims to understand the fundamental interaction mechanism between molybdenite and kaolinite in gypsum solution using kerosene as collector. Micro-flotation tests were conducted to study the effect of gypsum solution on the flotation performance of mixed −74 μm molybdenite and −10 μm kaolinite mineral. The results showed that the recovery of molybdenite decreased from 86% to 74% while the gypsum solution concentration increased from 0 to 800 mg/L, indicating the detrimental effect of kaolinite on molybdenite flotation could be enhanced by gypsum solution. This is mainly caused by the slime coating of kaolinite on molybdenite through dissolved calcium ion of gypsum solution. In order to confirm the slime coating phenomenon, zeta potential distribution, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were used to investigate interaction characteristics and mechanisms. The zeta potential distribution results revealed that mixed samples had the value between signal molybdenite and kaolinite samples in gypsum solution, which proved the coating phenomenon of kaolinite on molybdenite. Moreover, the coating phenomenon was becoming more and more obvious with the gypsum solution concentration. The coating phenomenon of kaolinite on molybdenite surface was also directly observed from SEM results. The AFM results provided further evidence for the possibility of slime coating, as the adhesion force increased with the gypsum solution concentration, which means the aggregates of molybdenite and kaolinite were becoming more stable. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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12 pages, 2578 KiB  
Article
Shkatulkalite, a Rare Mineral from the Lovozero Massif, Kola Peninsula: A Re-Investigation
by Andrey A. Zolotarev, Jr., Ekaterina A. Selivanova, Sergey V. Krivovichev, Yevgeny E. Savchenko, Taras L. Panikorovskii, Lyudmila M. Lyalina, Leonid A. Pautov and Victor N. Yakovenchuk
Minerals 2018, 8(7), 303; https://doi.org/10.3390/min8070303 - 18 Jul 2018
Cited by 8 | Viewed by 3537
Abstract
The crystal structure of shkatulkalite has been solved from the crystal from the Lovozero alkaline massif, Kola Peninsula, Russia. The mineral is monoclinic, P2/m, a = 5.4638(19), b = 7.161(3), c = 15.573(6) Å, β = 95.750(9)°, V = 606.3(4) [...] Read more.
The crystal structure of shkatulkalite has been solved from the crystal from the Lovozero alkaline massif, Kola Peninsula, Russia. The mineral is monoclinic, P2/m, a = 5.4638(19), b = 7.161(3), c = 15.573(6) Å, β = 95.750(9)°, V = 606.3(4) Å3, R1 = 0.080 for 1551 unique observed reflections. The crystal structure is based upon the HOH blocks consisting of one octahedral (O) sheet sandwiched between two heteropolyhedral (H) sheets. The blocks are parallel to the (001) plane and are separated from each other by the interlayer space occupied by Na1 atoms and H2O groups. The Na2, Na3, and Ti sites are located within the O sheet. The general formula of shkatulkalite can be written as Na5(Nb1−xTix)2(Ti1−yMn2+y)[Si2O7]2O2(OH)2·nH2O, where x + y = 0.5 and x ≈ y ≈ 0.25 for the sample studied. Shkatulkalite belongs to the seidozerite supergroup and is a member of the lamprophyllite group. The species most closely related to shkatulkalite are vuonnemite and epistolite. The close structural relations and the reported observations of pseudomorphs of shkatulkalite after vuonnemite suggest that, at least in some environments, shkatulkalite may form as a transformation mineral species. Full article
(This article belongs to the Special Issue Arctic Mineral Resources: Science and Technology)
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17 pages, 4332 KiB  
Article
Insights into Extinct Seafloor Massive Sulfide Mounds at the TAG, Mid-Atlantic Ridge
by Berit Lehrmann, Iain J. Stobbs, Paul A.J. Lusty and Bramley J. Murton
Minerals 2018, 8(7), 302; https://doi.org/10.3390/min8070302 - 18 Jul 2018
Cited by 13 | Viewed by 6766
Abstract
Over the last decade there has been an increasing interest in deep-sea mineral resources that may contribute to future raw metal supply. However, before seafloor massive sulfides (SMS) can be considered as a resource, alteration and weathering processes that may affect their metal [...] Read more.
Over the last decade there has been an increasing interest in deep-sea mineral resources that may contribute to future raw metal supply. However, before seafloor massive sulfides (SMS) can be considered as a resource, alteration and weathering processes that may affect their metal tenor have to be fully understood. This knowledge cannot be obtained by assessing the surface exposures alone. Seafloor drilling is required to gain information about the third dimension. In 2016, three extinct seafloor massive sulfide mounds, located in the Trans-Atlantic Geotraverse (TAG) hydrothermal area of the Mid-Atlantic Ridge were drilled. A mineralogical and textural comparison of drill core and surface-grab samples revealed that in recent ceased mounds high-temperature copper assemblages typical for black smoker chimneys are still present whereas in longer extinct mounds the mineralogy is pre-dominated by an iron mineral assemblage. Zinc becomes remobilized early in the mound evolution and forms either a layer in the upper part of the mound or has been totally leached from its interior. Precipitation temperatures of sphalerite calculated using the Fe/Zn ratio can help to identify these remobilization processes. While the Fe/Zn ratios of primary sphalerites yield temperatures that are in very good agreement with fluid temperatures measured in white smokers, calculated temperatures for sphalerites affected by remobilization are too high for SMS. Overall drilling of SMS provides valuable information on the internal structure and mineralogy of the shallow sub-surface, however, additional drilling of SMS, at a greater depth, is required to fully understand the processes affecting SMS and their economic potential. Full article
(This article belongs to the Special Issue Deep-Sea Minerals and Gas Hydrates)
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15 pages, 2737 KiB  
Article
Carbon Material with High Specific Surface Area Improves Complex Copper Ores’ Bioleaching Efficiency by Mixed Moderate Thermophiles
by Xiaodong Hao, Xueduan Liu, Ping Zhu, Aijia Chen, Hongwei Liu, Huaqun Yin, Guanzhou Qiu and Yili Liang
Minerals 2018, 8(7), 301; https://doi.org/10.3390/min8070301 - 16 Jul 2018
Cited by 11 | Viewed by 3651
Abstract
The catalysis of carbon materials with different specific surface areas (SSA) (2, 400, 800 and 1200 m2/g) on complex copper ores bioleaching by moderately mixed thermophiles was investigated. The copper extractions increased with the rise in SSA of carbon materials. A [...] Read more.
The catalysis of carbon materials with different specific surface areas (SSA) (2, 400, 800 and 1200 m2/g) on complex copper ores bioleaching by moderately mixed thermophiles was investigated. The copper extractions increased with the rise in SSA of carbon materials. A recovery of 98.8% copper in the presence of 1200 m2/g activated carbon was achieved, and improved by 30.7% and 76.4% compared with biotic control and chemical leaching. Moreover, the addition of 1200 m2/g activated carbon adsorbed large amount of bacteria, accelerated the oxidation rate of ferrous iron and maintained the solution redox potential at relatively low values, and significantly increased the dissolution of primary copper sulfide (62.7%) compared to biotic control (6.0%). Microbial community succession revealed that activated carbon changed the microbial community composition dramatically. The S. thermosulfidooxidans ST strain gained a competitive advantage and dominated the microbial community through the whole bioleaching process. The promoting effect of carbon material with higher SSA on copper extraction was mainly attributed to better galvanic interaction, biofilm formation, direct contact and lower redox potential. Full article
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23 pages, 41465 KiB  
Article
Quantitative 3D Association of Geological Factors and Geophysical Fields with Mineralization and Its Significance for Ore Prediction: An Example from Anqing Orefield, China
by Yaozu Qin and Liangming Liu
Minerals 2018, 8(7), 300; https://doi.org/10.3390/min8070300 - 13 Jul 2018
Cited by 22 | Viewed by 4066
Abstract
Quantitative 3D spatial association of geological factors and geophysical fields with orebodies is critical for ore prediction. The Anqing orefield, a principal Cu–Fe orefield in China, is closely associated with the Yueshan intrusion. By compiling the data from drilling and tunnelling exploration, Controlled [...] Read more.
Quantitative 3D spatial association of geological factors and geophysical fields with orebodies is critical for ore prediction. The Anqing orefield, a principal Cu–Fe orefield in China, is closely associated with the Yueshan intrusion. By compiling the data from drilling and tunnelling exploration, Controlled Source Audiofrequency Magnetotelluric (CSAMT) surveying and the computational modelling of magmatic intrusion’s cooling process, we constructed models of the Yueshan intrusion, ore-favourable carbonate formation, orebodies, resistivity field and volume strain field. These models are used as evidential factors to analyse their spatial association with mineralization by the weights-of-evidence (WofE) method. The location of orebodies is closely related to the shape of the contact zone of the Yueshan intrusion. The spaces with the distance ≤200 m to the concaves that were selected by minimum principal curvature (|Kmin| ≥ 0.0025) from contact zones, are very favourable for localization of orebodies. Most orebodies are not located in the spaces of the lowest resistivity, suggesting that the lowest resistivity cannot be used as an indicator for mineralization. The spaces with higher positive volumetric strain have higher positive weights with orebodies, implying that the mineralization is positively related to the positive volumetric strain. The spaces of all evidential factors that had positive correlation with mineralization were integrated to create a 3D prospectivity map by calculating posterior probability. Five areas with higher posterior probability, indicating higher prospectivity potential, are selected as targets for future exploration. Full article
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21 pages, 13097 KiB  
Review
Fly Ash-Based Geopolymer Binder: A Future Construction Material
by Nakshatra B. Singh
Minerals 2018, 8(7), 299; https://doi.org/10.3390/min8070299 - 12 Jul 2018
Cited by 171 | Viewed by 30426
Abstract
A large amount of waste coming out from industries has posed a great challenge in its disposal and effect on the environment. Particularly fly ash, coming out from thermal power plants, which contains aluminosilicate minerals and creates a lot of environmental problems. In [...] Read more.
A large amount of waste coming out from industries has posed a great challenge in its disposal and effect on the environment. Particularly fly ash, coming out from thermal power plants, which contains aluminosilicate minerals and creates a lot of environmental problems. In recent years, it has been found that geopolymer may give solutions to waste problems and environmental issues. Geopolymer is an inorganic polymer first introduced by Davidovits. Geopolymer concrete can be considered as an innovative and alternative material to traditional Portland cement concrete. Use of fly ash as a raw material minimizes the waste production of thermal power plants and protects the environment. Geopolymer concretes have high early strength and resistant to an aggressive atmosphere. Methods of preparation and characterization of fly ash-based geopolymers have been presented in this paper. The properties of geopolymer cement/mortar/concrete under different conditions have been highlighted. Fire resistance properties and 3D printing technology have also been discussed. Full article
(This article belongs to the Special Issue Geopolymers)
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24 pages, 9380 KiB  
Article
Geochemical Characterization of Bauxite Deposits from the Abruzzi Mining District (Italy)
by Francesco Putzolu, Armando Piccolo Papa, Nicola Mondillo, Maria Boni, Giuseppina Balassone and Angela Mormone
Minerals 2018, 8(7), 298; https://doi.org/10.3390/min8070298 - 12 Jul 2018
Cited by 52 | Viewed by 7709
Abstract
The Abruzzi bauxite district includes the deposits located on the Campo Felice plateau and those of the Monti d’Ocre, which had been mined in the first part of the 20th century. Bauxite is of the karst type, with textures ranging between oolitic and [...] Read more.
The Abruzzi bauxite district includes the deposits located on the Campo Felice plateau and those of the Monti d’Ocre, which had been mined in the first part of the 20th century. Bauxite is of the karst type, with textures ranging between oolitic and oolitic-conglomeratic, the latter suggesting a partial reworking of evolved lateritic soils. The high contents of Al2O3 and Fe2O3 (average values 53.76 and 21.76 wt %, respectively) are associated with the presence of boehmite, hematite, and minor goethite. SiO2 and TiO2 have average values of 7.79 and 2.75 wt %, corresponding to the presence of kaolinite, anatase and rutile. Among the minor so-called “bauxitophile” elements V, Co, Ni, Cr and Zr, the most enriched is Cr, with an average value of 0.07 wt %. Nickel has an average value of 210.83 ppm. Vanadium shows an average value of 266.57 ppm, whereas the average Co concentration is 35.89 ppm. The total rare earth elements (REE) concentration in the sampled bauxite sites is variable between ca. 700 and 550 ppm. Among REEs, the most abundant element is Ce, with Ce anomalies commonly associated with authigenic REE-fluoro-carbonates, probably produced after the REEs remobilization from primary detrital minerals and their precipitation in neo-formed phases during the bauxitization process. Scandium and Ga occur in small amounts (57 and 60 ppm, respectively), but geochemical proxies of their remobilization and uptake in neo-formed minerals (Fe- and Al-(hydr)oxides, respectively) have been observed. The mean Eu/Eu* and Al2O3/TiO2 ratios and the Ni-Cr contents of the Abruzzi bauxites suggest that the parent rock of these deposits was a material of acid affinity, likely corresponding to volcanic tephra or eolic loess-type sands. Full article
(This article belongs to the Special Issue Bauxite Deposits)
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22 pages, 4260 KiB  
Article
Mineralogical and Geochemical Characteristics of Trace Elements in the Yongdingzhuang Mine, Datong Coalfield, Shanxi Province, China
by Yue Yuan, Shuheng Tang, Songhang Zhang and Ning Yang
Minerals 2018, 8(7), 297; https://doi.org/10.3390/min8070297 - 11 Jul 2018
Cited by 13 | Viewed by 3288
Abstract
Fifteen samples of No. 4 coal from the Yongdingzhuang Mine in Datong Coalfield were tested for their elemental compositions, modes of occurrence, and mineralogical compositions, using X-ray powder diffraction, X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, and scanning electron microscopy equipped with [...] Read more.
Fifteen samples of No. 4 coal from the Yongdingzhuang Mine in Datong Coalfield were tested for their elemental compositions, modes of occurrence, and mineralogical compositions, using X-ray powder diffraction, X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, and scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer. The samples have low sulfur content (0.63%). The major minerals are kaolinite and quartz, followed by pyrite and anatase. Compared with averages for the Chinese coals, the percentages of SiO2 (15.11%), TiO2 (0.7%), and Al2O3 (10.39%) are much higher. In No. 4 coals, Li (62.81 μg/g), Be (6.94 μg/g), Zr (235 μg/g), Ga (17.04 μg/g), F (165.53 μg/g), Tl (1.93 μg/g), and Hg (0.34 μg/g) are some potentially valuable and toxic trace elements with higher concentrations than Chinese coals and World hard coals. Lithium and F mainly have kaolinite associations. With the exception of kaolinite, Li, and F also partly occur in anatase, gorceixite and goyazite. Beryllium largely occurs in anatase; gallium is mainly associated with kaolinite and to a lesser extent, with gorceixite and goyazite; zirconium is associated with kaolinite, gorceixite and goyazite; and thallium and Hg occur in in pyrite. Potentially valuable elements (including Al, Li, Ga, and Zr) might be recovered as value-added byproducts from coal ash. Toxic elements (e.g., Be, F, Tl, and Hg) might have potential adverse effects to the environment and human health during coal processing. In addition, the distribution patterns of rare earth elements and yttrium (REY) indicate that the REY in No. 4 coals originated from the granite of Yinshan Oldland, and natural waters or hydrothermal solutions that may circulate in coal basins. Full article
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13 pages, 8588 KiB  
Article
Selective Fabrication of Barium Carbonate Nanoparticles in the Lumen of Halloysite Nanotubes
by Jing Ouyang, Dawei Mu, Yi Zhang, Huaming Yang and Steven L. Suib
Minerals 2018, 8(7), 296; https://doi.org/10.3390/min8070296 - 11 Jul 2018
Cited by 12 | Viewed by 4430
Abstract
Barium carbonate (BaCO3) materials with the controllable morphology of nanoparticles were selectively loaded into the lumen halloysite nanotubes (abbreviated as Hal) by a urease assisted catalytic implementation strategy. The Hal mineral was pre-treated through leaching by hydrochloric acid (abbreviated as A-Hal), [...] Read more.
Barium carbonate (BaCO3) materials with the controllable morphology of nanoparticles were selectively loaded into the lumen halloysite nanotubes (abbreviated as Hal) by a urease assisted catalytic implementation strategy. The Hal mineral was pre-treated through leaching by hydrochloric acid (abbreviated as A-Hal), resulting in increased defect sites and zeta potential. The negatively charged urease was loaded inside the positively charged A-Hal lumen, and then through the decomposition of urea catalyzed by urease to produce carbonate ions and ammonia. When Ba2+ diffused in, BaCO3 particles were selectively synthesized in the lumen of A-Hal, the pore channels of A-Hal effectively controlled the growth and aggregation of BaCO3 nanocrystals and their geometrical morphology. The obtained BaCO3/A-Hal-T was characterized by transmission electron microscopy, Fourier transformation infrared spectroscopy and X-ray diffraction, differential scanning calorimetry-thermogravimetry (DSC-TG). The BaCO3/A-Hal-T may provide a candidate for potential applications. Full article
(This article belongs to the Special Issue Mineral Materials)
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18 pages, 1835 KiB  
Article
Reprocessing of a Southern Chilean Zn Tailing by Flotation—A Case Study
by Bent Babel, Maike Penz, Edgar Schach, Stefanie Boehme and Martin Rudolph
Minerals 2018, 8(7), 295; https://doi.org/10.3390/min8070295 - 11 Jul 2018
Cited by 20 | Viewed by 6246
Abstract
The reprocessing of tailings can have economic and environmental benefits compared to the processing of primary ore deposits. In this paper we present the characterization of a tailings dam in southern Chile by means of mineralogical and geochemical investigations, focusing on sphalerite and [...] Read more.
The reprocessing of tailings can have economic and environmental benefits compared to the processing of primary ore deposits. In this paper we present the characterization of a tailings dam in southern Chile by means of mineralogical and geochemical investigations, focusing on sphalerite and trace elements with the aim to investigate a potential reprocessing. The assessment is followed by a flotation study, focusing on the recovery of sphalerite with a high selectivity towards sulfidic and non-sulfidic gangue minerals. An in-depth analysis of a selected test based on mineral liberation analysis data is used to refine the liberation, concentration and flotation weighting function for future investigations. Full article
(This article belongs to the Special Issue Geometallurgy)
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18 pages, 8901 KiB  
Article
The Effects of Sodium Ions, Phosphorus, and Silicon on the Eco-Friendly Process of Vanadium Precipitation by Hydrothermal Hydrogen Reduction
by Guobin Zhang, Yimin Zhang and Shenxu Bao
Minerals 2018, 8(7), 294; https://doi.org/10.3390/min8070294 - 11 Jul 2018
Cited by 11 | Viewed by 3467
Abstract
The effects of sodium ions, phosphorus, and silicon on the eco-friendly process of vanadium precipitation by hydrothermal hydrogen reduction were investigated to establish the suitable concentrated solution system for this eco-friendly process. The results showed that sodium ions had no negative effects on [...] Read more.
The effects of sodium ions, phosphorus, and silicon on the eco-friendly process of vanadium precipitation by hydrothermal hydrogen reduction were investigated to establish the suitable concentrated solution system for this eco-friendly process. The results showed that sodium ions had no negative effects on the vanadium precipitation process. Phosphorus can reduce vanadate ion activity, and results in the decrease of vanadium precipitation percentage from 99.5% to 61.3%, as the phosphorus concentration in the feed solution increased from 0.05 g/L to 3 g/L. As a result, the aimed products of V2O3 were hard to be obtained, and the purity of the precipitates was lowered. Silicon can absorb in the form of H3Si3O7 on the surface of the precipitates, thus it was difficult for H (activity hydrogen atom) to react with the intermediate vanadium-bearing precipitates. As a result, the vanadium precipitation percentage decreased from 99.5% to 86.2% as the silicon concentration in the feed solution increased from 0.1 g/L to 3 g/L. The aimed products of V2O3 were not easy to be obtained, and only the intermediate vanadium-bearing precipitates containing sodium ions were obtained. The upper limits of the concentrations of phosphorus and silicon in the feed V (V) solution were ascertained as 0.5 g/L and 0.1 g/L, respectively. As the concentrations of phosphorus and silicon in the purified alkaline-concentrated V (V) solution extracted from vanadium-bearing shale are usually below the upper limits of the concentrations, the eco-friendly process of vanadium precipitation by hydrothermal hydrogen reduction has a great application prospect in the field of vanadium extraction from vanadium-bearing shale. Full article
(This article belongs to the Special Issue Towards Sustainability in Extractive Metallurgy)
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20 pages, 4446 KiB  
Article
Geochemistry, Zircon U–Pb Age, and Lu–Hf Isotope of the Granite Porphyry in Leimengou Mo Deposit in the East Qinling Molybdenum Ore Belt, China
by Jing Cao, Huishou Ye, Xiaodan Chen, Wen He and Peng Wang
Minerals 2018, 8(7), 293; https://doi.org/10.3390/min8070293 - 10 Jul 2018
Cited by 13 | Viewed by 3550
Abstract
The Leimengou Mo deposit is one of the typical porphyry deposits in the East Qinling molybdenum ore belt. The Mo mineralization mainly hosts in the Leimengou intrusion, with minor by the gneiss of Archean Taihua Group. The Leimengou intrusion is composed of granite [...] Read more.
The Leimengou Mo deposit is one of the typical porphyry deposits in the East Qinling molybdenum ore belt. The Mo mineralization mainly hosts in the Leimengou intrusion, with minor by the gneiss of Archean Taihua Group. The Leimengou intrusion is composed of granite porphyry and monzonitic granite porphyry. Zircon U–Pb LA-(MC)-ICP-MS dating of the two rocks yield the same age of 131 ± 0.6 Ma (N = 23, MSWD = 1.6), consistent with 132 ± 2 Ma of Mo mineralization age obtained by the Re–Os method. The Leimengou intrusion is peraluminous (A/CNK = 1.06–1.28) and high-K calc-alkaline series (K2O + Na2O = 7.84%–9.07%). The REE and trace elements are enriched in large ion lithophile elements (LREE, K, Rb, Ba, Sr, Th and U), and depleted in high-field strength elements (HREE, Nb, Ti and P), with moderately negative abnormal of Eu. Both granite porphyry and monzonitic granite porphyry show a large variation in zircon Hf isotopic compositions with εHf(t) values of −27.9 to −16.9 and −26.0 to −15.2, and two-stage model ages of 2259 to 2946 Ma and 2149 to 2827 Ma, respectively. Whole rock geochemistry and zircon Lu–Hf isotopic compositions suggest that the Leimengou intrusion was derived mainly from an ancient continental crust (probably Archean Taihua Group), with the addition of mantle-derived components. Full article
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30 pages, 12307 KiB  
Article
Three-D Mineralogical Mapping of the Kovdor Phoscorite-Carbonatite Complex, NW Russia: II. Sulfides
by Gregory Yu. Ivanyuk, Yakov A. Pakhomovsky, Taras L. Panikorovskii, Julia A. Mikhailova, Andrei O. Kalashnikov, Ayya V. Bazai, Victor N. Yakovenchuk, Nataly G. Konopleva and Pavel M. Goryainov
Minerals 2018, 8(7), 292; https://doi.org/10.3390/min8070292 - 9 Jul 2018
Cited by 7 | Viewed by 4248
Abstract
The world largest phoscorite-carbonatite complexes of the Kovdor (Russia) and Palabora (South Africa) alkaline-ultrabasic massifs have comparable composition, structure and metallogenic specialization, and can be considered close relatives. Distribution of rock-forming sulfides within the Kovdor phoscorite-carbonatite complex reflects gradual concentric zonation of the [...] Read more.
The world largest phoscorite-carbonatite complexes of the Kovdor (Russia) and Palabora (South Africa) alkaline-ultrabasic massifs have comparable composition, structure and metallogenic specialization, and can be considered close relatives. Distribution of rock-forming sulfides within the Kovdor phoscorite-carbonatite complex reflects gradual concentric zonation of the pipe: pyrrhotite with exsolution inclusions of pentlandite in marginal (apatite)-forsterite phoscorite, pyrrhotite with exsolution inclusions of cobaltpentlandite in intermediate low-carbonate magnetite-rich phoscorite and chalcopyrite (±pyrrhotite with exsolution inclusions of cobaltpentlandite) in axial carbonate-rich phoscorite and phoscorite-related carbonatite. Chalcopyrite (with relicts of earlier bornite and exsolution inclusions of cubanite and mackinawite) predominates in the axial carbonate-bearing phoscorite and carbonatite, where it crystallizes around grains of pyrrhotite (with inclusions of pentlandite-cobaltpentlandite and pyrite), and both of these minerals contain exsolution inclusions of sphalerite. In natural sequence of the Kovdor rocks, iron content in pyrrhotite gradually increases from Fe7S8 (pyrrhotite-4C, Imm2) to Fe9S10 (pyrrhotite-5C, C2 and P21) and Fe11S12 (pyrrhotite-6C) due to gradual decrease of crystallization temperature and oxygen fugacity. Low-temperature pyrrhotite 2C (troilite) occurs as lens-like exsolition inclusions in grains of pyrrhotite-4C (in marginal phoscorite) and pyrrhotite-5C (in axial phoscorite-related carbonatite). Within the phoscorite-carbonatite complex, Co content in pyrrhotite gradually increases from host silicate rocks and marginal forsterite-dominant phoscorite to axial carbonate-rich phoscorite and carbonatite at the expense of Ni and Fe. Probably, this dependence reflects a gradually decreasing temperature of the primary monosulfide solid solutions crystallization from the pipe margin toward its axis. The Kovdor and Loolekop phoscorite-carbonatite pipes in the Palabora massif have similar sequences of sulfide formation, and the copper specialization of the Palabora massif can be caused by higher water content in its initial melt allowing it to dissolve much larger amounts of sulfur and, correspondingly, chalcophile metals. Full article
(This article belongs to the Special Issue Arctic Mineral Resources: Science and Technology)
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24 pages, 5118 KiB  
Article
Geochemistry and Biomarker Analysis of the Bentonites from Esquivias (Toledo, Spain)
by Javier García-Rivas, Mercedes Suárez, Trinidad Torres, Yolanda Sánchez-Palencia, Emilia García-Romero and José E. Ortiz
Minerals 2018, 8(7), 291; https://doi.org/10.3390/min8070291 - 9 Jul 2018
Cited by 5 | Viewed by 3891
Abstract
The Tajo Basin is one of the richest in Mg-clays known around the world. Mg-bentonites, kwon as pink clays and green clays, alter in the Intermediate Unit of the Miocene sediments. In this work, a new approach to the genesis of these bentonites [...] Read more.
The Tajo Basin is one of the richest in Mg-clays known around the world. Mg-bentonites, kwon as pink clays and green clays, alter in the Intermediate Unit of the Miocene sediments. In this work, a new approach to the genesis of these bentonites is performed by studying for the first time the biomarkers present in these clays in relation to the mineralogy and geochemistry, as well as using discriminatory criteria between green and pink clays. Samples were collected at a quarry of Mg-bentonites, in the proximities of Esquivias (Toledo, Spain). Mineralogical characterization and semi-quantification (X-ray diffraction (XRD)) allowed a well-defined classification according to the mineralogical content of the samples to be established, differentiating four associations. Geochemical analyses are clearly linked to the mineralogy and provide criteria to differentiate the genesis of the materials studied. In this regard, green clays are interpreted as having a more detrital character than pink clays, which present a more authigenic character. Biomarkers (n-alkanes and n-alkanoic acids) were studied, not showing a clear link with the mineralogy as in the case of the geochemistry, but providing interesting information about the origin and degradation of the organic matter. Pink clays have higher contents in biomarkers than green clays, providing a discriminative criterion. Full article
(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)
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13 pages, 3816 KiB  
Article
Distribution and Characteristics of Nanotubular Halloysites in the Thach Khoan Area, Phu Tho, Vietnam
by Bui Hoang Bac, Nguyen Tien Dung, Luong Quang Khang, Khuong The Hung, Nguyen Van Lam, Do Manh An, Phan Viet Son, Tran Thi Van Anh, Doan Van Chuong and Bui Thanh Tinh
Minerals 2018, 8(7), 290; https://doi.org/10.3390/min8070290 - 8 Jul 2018
Cited by 13 | Viewed by 5249
Abstract
Two types of halloysite collected from the upper (UPS) and lower (LOS) zones of a weathered pegmatite profile in the Thach Khoan area, Phu Tho were defined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy [...] Read more.
Two types of halloysite collected from the upper (UPS) and lower (LOS) zones of a weathered pegmatite profile in the Thach Khoan area, Phu Tho were defined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermal analysis (TG and DTG), and N2 adsorption-desorption isotherms. XRD analysis showed that halloysite and kaolinite coexist in samples of size fractions <2 µm. Semi-quantitative analysis by XRD after formamide (FA) treatment indicated that the halloysite contents are approximately 81% and 93% in UPS and LOS samples, respectively. The results of SEM and TEM analyses showed that while short halloysite type is mainly distributed in the upper zone, long halloysite type occurs primarily in the lower zone of the weathered pegmatite profile. The length of short halloysite ranging from 250 to 750 nm is most popular, accounting for 47.2% of halloysites in the UPS sample. Meanwhile, long halloysites which have the length of 750–1250 nm are dominant in the LOS sample with 69.9%. In addition, short halloysites with outer diameter of >100 nm constitute 79.1% of halloysites in the UPS sample while long halloysites with outer diameter of 50–100 nm make up 74.2% of halloysites in LOS sample. Specific surface areas are 15.7434 and 22.0211 m2/g and average pore sizes are 18.9837 and 17.0281 nm for the UPS and LOS samples, respectively. The analysis implies that although forming under same natural geographical and climatic conditions, halloysites at different depths in the weathered pegmatite profile may have different morphological and other properties. Full article
(This article belongs to the Special Issue Mineral Materials)
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16 pages, 10559 KiB  
Article
Origins and Geochemistry of Dolomites and Their Dissolution in the Middle Triassic Leikoupo Formation, Western Sichuan Basin, China
by Shunli Zhang, Zhengxiang Lv, Yi Wen and Sibing Liu
Minerals 2018, 8(7), 289; https://doi.org/10.3390/min8070289 - 6 Jul 2018
Cited by 19 | Viewed by 6478
Abstract
Triassic dolomites occur pervasively in the Western Sichuan Basin. Although these strata have been deeply buried and affected by multiple phases of dolomitization and dissolution, some intervals in the upper part of the Leikoupo Formation have developed high porosity. Based on their petrographic [...] Read more.
Triassic dolomites occur pervasively in the Western Sichuan Basin. Although these strata have been deeply buried and affected by multiple phases of dolomitization and dissolution, some intervals in the upper part of the Leikoupo Formation have developed high porosity. Based on their petrographic and geochemical features, three major types of dolomite fabrics are recognized, namely, dolomicrite, fabric-retentive dolomite, and fabric-destructive dolomite. Geochemical evidence indicates that the dolomicrite formed following the Sabkha model in a low-temperature hypersaline environment, as these rocks exhibit abnormally high Sr and Na contents, lower Fe and Mn contents, δ18O values generally ranging from −1.70‰ to −1.67‰ (with an average value of −1.69‰), and higher Mg/Ca ratios. The fabric-retentive dolomite formed following the seepage-reflux model in a shallow burial environment, and these rocks exhibit the highest 87Sr/86Sr ratios, δ18O values generally ranging from −6.10‰ to −2.50‰ (with an average value of −3.98‰), and a wide range of Fe and Mn contents, indicating that they may have been altered by meteoric water. The fabric-destructive dolomite formed following the burial model at elevated temperatures; these rocks exhibit the lowest Sr and Na contents, δ18O values generally ranging from −7.01‰ to −6.62‰ (with an average value of −6.79‰), relatively higher Mg/Ca values, and lower 87Sr/86Sr ratios. The early Sabkha, seepage-reflux dolomitization and penecontemporaneous periodic meteoric freshwater selective dissolution processes formed multi-period, overlapping moldic pores, algal framework pores, and intragranular dissolution pores. The superposition of organic acid dissolution during the burial period is the main controlling factor of the formation of deeply buried, high-quality dolomite reservoirs in the Leikoupo Formation. Full article
(This article belongs to the Special Issue Mineralogy, Petrology, Geochemistry and Diagenesis of Carbonate Minerals and Rocks)
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16 pages, 2408 KiB  
Article
Distribution and Chemical Speciation of Molybdenum in River and Pond Sediments Affected by Mining Activity in Erdenet City, Mongolia
by Tsetsgee Solongo, Keisuke Fukushi, Ochir Altansukh, Yoshio Takahashi, Akitoshi Akehi, Gankhurel Baasansuren, Yunden Ariuntungalag, Odgerel Enkhjin, Boldbaatar Davaajargal, Davaasuren Davaadorj and Noriko Hasebe
Minerals 2018, 8(7), 288; https://doi.org/10.3390/min8070288 - 5 Jul 2018
Cited by 23 | Viewed by 6691
Abstract
Rivers and ponds near the Erdenet mine, one of the world’s largest copper-molybdenum mines, exhibit high concentrations of molybdenum (Mo). This study evaluates the distribution and chemical speciation of Mo in surface sediments from ponds and rivers in Erdenet city to elucidate the [...] Read more.
Rivers and ponds near the Erdenet mine, one of the world’s largest copper-molybdenum mines, exhibit high concentrations of molybdenum (Mo). This study evaluates the distribution and chemical speciation of Mo in surface sediments from ponds and rivers in Erdenet city to elucidate the mobility and solubility of Mo in the surface aquatic environments in the area. The waters and sediments were collected in two shallow ponds connected to the tailing pond and from three rivers flowing through Erdenet city. The distribution and chemical speciation of Mo in the sediments were examined using five-step sequential extraction and X-ray absorption fine structure (XAFS) analyses. The XAFS spectra of the sediments showed that large amounts of Mo in the sediments are molybdate or polymeric molybdate, weakly adsorbed onto ferrihydrite. Sequential extraction consistently showed a large amount of Mo distributed in the labile fractions. Results suggest that the surface sediments from ponds and rivers play a role as secondary contamination sources of Mo rather than as sinks of Mo in the area. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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20 pages, 3534 KiB  
Article
REE and Y Mineralogy of the Krudum Granite Body (Saxothuringian Zone)
by Miloš René
Minerals 2018, 8(7), 287; https://doi.org/10.3390/min8070287 - 5 Jul 2018
Cited by 5 | Viewed by 4960
Abstract
The Krudum granite body comprises highly fractionated granitic rocks ranging from medium-F biotite granites to high-F, high-P2O5 Li-mica granites. This unique assemblage is an ideal site to continue recent efforts in petrology to characterize the role of zircon, monazite, and [...] Read more.
The Krudum granite body comprises highly fractionated granitic rocks ranging from medium-F biotite granites to high-F, high-P2O5 Li-mica granites. This unique assemblage is an ideal site to continue recent efforts in petrology to characterize the role of zircon, monazite, and xenotime as hosts to rare earth elements (REEs). The granitic rocks of the Krudum body analyzed in this study were found to contain variable concentrations of monazite and zircon, while xenotime was only found in the high-F, high-P2O5 Li-mica granites and in the alkali-feldspar syenites of the Vysoký Kámen stock. Intermediate trends between cheralite and huttonite substitutions are characteristic for analyzed monazite grains from all magmatic suites. The highest concentration of cheralite was found in monazite from the alkali-feldspar syenites (up to 69.3 mol %). The proportion of YPO4 in analyzed xenotime grains ranges from 71 to 84 mol %. Xenotime grains are commonly enriched in heavy rare earth elements (HREEs; 9.3–19.5 wt % HREE2O3) and thorite-coffinite and cheralite exchange was observed. Some xenotime analyses return low totals, suggesting their hydration during post-magmatic alterations. Analyzed zircon from granite suites of the Krudum granite body contains moderate Hf concentrations (1.0–4.7 wt % HfO2; 0.010–0.047 apfu Hf). The highest concentrations of HfO2 were found in zircon from the high-F, high-P2O5 Li-mica granites (1.2–4.7 wt % HfO2). Analyzed zircon grains from the high-F, high-P2O5 Li-mica granites and alkali-feldspar syenites are enriched in P (up to 8.29 wt % P2O5; 0.24 apfu P), Al (0.02–2.0 wt % Al2O3; 0.00–0.08 apfu Al), Ca (up to 3.9 wt % CaO; 0.14 apfu Ca), Y (up to 5.5 wt % Y2O3; 0.10 apfu Y), and Sc (up to 1.17 wt % Sc2O3; 0.03 apfu Sc). Zircon grains from the high-F, high-P2O5 Li-mica granites were sometimes hydrated and fluorized. The concentrations of F in zircon from partly greisenised high-F, high-P2O5 Li-mica granites reached up to 1.2 wt % (0.26 apfu F). Full article
(This article belongs to the Special Issue Mineral Deposits of Critical Elements)
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15 pages, 3593 KiB  
Article
Stability of AuCl2− from 25 to 1000 °C at Pressures to 5000 bar and Consequences for Hydrothermal Gold Mobilization
by Alexander V. Zotov, Nikolai N. Kuzmin, Vladimir L. Reukov and Boris R. Tagirov
Minerals 2018, 8(7), 286; https://doi.org/10.3390/min8070286 - 4 Jul 2018
Cited by 24 | Viewed by 5027
Abstract
Gold is transported in high-temperature chloride-bearing hydrothermal fluids in the form of AuCl2−. The stability of this complex has been extensively studied, but there is still considerable disagreement between available experimental data on the temperature region 300–500 °C. To solve [...] Read more.
Gold is transported in high-temperature chloride-bearing hydrothermal fluids in the form of AuCl2−. The stability of this complex has been extensively studied, but there is still considerable disagreement between available experimental data on the temperature region 300–500 °C. To solve this problem, we measured the solubility of gold in HCl/NaCl fluids (NaCl concentration varied from 0.1 to 3 mol·(kg·H2O)−1) at 450 °C and pressures from 500 to 1500 bar (1 bar = 105 Pa). The experiments were performed using a batch autoclave method at contrasting redox conditions: in reduced experiments hydrogen was added to the autoclave, and in oxidized experiments the redox state was controlled by the aqueous SO2/SO3 buffer. Hydrogen pressure in the autoclaves was measured after the experiments in the reduced system. The gold solubility constant, Au(cr) + HCl°(aq) + Cl− = AuCl2− + 0.5 H2°(aq), was determined for the experimental T-P parameters as log Ks° = −4.77 ± 0.07 (500 bar), −5.11 ± 0.08 (1000 bar), and −5.43 ± 0.09 (1500 bar). These data, together with values from the literature for temperatures from 25 to 1000 °C, were fitted to the simple equation log Ks° = 4.302 − 7304∙T(K)−1 − 4.77∙log d(w) + 11080∙(log d(w))∙T(K)−1 − 6.94 × 106∙(log d(w)) T(K)−2, where d(w) is the pure water density. This equation can be used together with the extended Debye–Hückel equation for activity coefficients to calculate gold solubility at pressures up to 5000 bar at fluid chlorinities at least up to 30 wt %. The speciation of gold in natural chloride-bearing fluids is discussed. Full article
(This article belongs to the Special Issue Experimental and Thermodynamical Modeling of Ore-Forming Processes in Magmatic and Hydrothermal Systems)
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36 pages, 40685 KiB  
Article
High-Resolution Analysis of Critical Minerals and Elements in Fe–Mn Crusts from the Canary Island Seamount Province (Atlantic Ocean)
by Egidio Marino, Francisco Javier González, Rosario Lunar, Jesús Reyes, Teresa Medialdea, Mercedes Castillo-Carrión, Eva Bellido and Luis Somoza
Minerals 2018, 8(7), 285; https://doi.org/10.3390/min8070285 - 2 Jul 2018
Cited by 50 | Viewed by 8473
Abstract
Two Fe–Mn crusts among 35 samples, from six seamounts in the Canary Island Seamount Province, were selected as representatives of the endpoint members of two distinct types of genetic processes, i.e., mixed diagenetic/hydrogenetic and purely hydrogenetic. High-resolution analyses pursued the main aim of [...] Read more.
Two Fe–Mn crusts among 35 samples, from six seamounts in the Canary Island Seamount Province, were selected as representatives of the endpoint members of two distinct types of genetic processes, i.e., mixed diagenetic/hydrogenetic and purely hydrogenetic. High-resolution analyses pursued the main aim of distinguishing the critical elements and their association with mineral phases and genetic processes forming a long-lived Fe–Mn crust. The Fe–Mn crust collected on the Tropic Seamount is composed of dense laminations of Fe-vernadite (>90%) and goethite group minerals, reflecting the predominance of the hydrogenetic process during their formation. Based on high-resolution age calculation, this purely hydrogenetic crust yielded an age of 99 Ma. The Fe–Mn crust collected on the Paps Seamount shows a typical botryoidal surface yielding an age of 30 Ma. electron probe microanalyzer (EPMA) spot analyses show two main types of manganese oxides, indicating their origin: (i) hydrogenetic Fe-vernadite, the main Mn oxide, and (ii) laminations of interlayered buserite and asbolane. Additionally, the occurrence of calcite, authigenic carbonate fluor-apatite (CFA) and palygorskite suggests early diagenesis and pervasive phosphatization events. Sequential leaching analysis indicated that Co, Ni, Cu, Ba and Ce are linked to Mn minerals. Therefore, Mn-oxides are enriched in Ni and Cu by diagenetic processes or in Co and Ce by hydrogenetic processes. On the other hand, Fe-oxides concentrate V, Zn, As and Pb. Moreover, the evidence of HREE enrichment related to Fe-hydroxides is confirmed in the mixed hydrogenetic/diagenetic crust. Full article
(This article belongs to the Special Issue Deep-Sea Minerals and Gas Hydrates)
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27 pages, 2208 KiB  
Review
Mining Waste and Its Sustainable Management: Advances in Worldwide Research
by José A. Aznar-Sánchez, José J. García-Gómez, Juan F. Velasco-Muñoz and Anselmo Carretero-Gómez
Minerals 2018, 8(7), 284; https://doi.org/10.3390/min8070284 - 2 Jul 2018
Cited by 104 | Viewed by 12472
Abstract
Growing social awareness of the need to adequately treat mining waste in order to protect the environment has led to an increase in the research in this field. The aim of this study was to analyze the dynamics of the research focused on [...] Read more.
Growing social awareness of the need to adequately treat mining waste in order to protect the environment has led to an increase in the research in this field. The aim of this study was to analyze the dynamics of the research focused on mining waste and its sustainable management on a worldwide scale from 1988 to 2017. A systematic review and a bibliometric analysis of 3577 articles were completed. The results show that research into mining waste has increased, with studies focusing on waste management accounting for almost 40% of the total. The most productive journals in this field were Applied Geochemistry and Science of the Total Environment. The five most productive countries were the United States, Canada, Spain, Australia, and China. Works on the sustainable management of mining waste were in the minority, but it is an area of research that has considerable potential given the growing social awareness of the environmental repercussions of mining activities and the demands for increasingly sustainable practices. The findings of this study could prove useful for studies into mine waste, as they depict a global view of this line of research. Full article
(This article belongs to the Special Issue Towards a Sustainable Management of Mine Wastes: Reprocessing, Reuse, Revalorization and Repository)
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16 pages, 2247 KiB  
Article
Comparative Analysis of the Siliceous Source and Organic Matter Enrichment Mechanism of the Upper Ordovician–Lower Silurian Shale in the Upper-Lower Yangtze Area
by Kun Zhang, Zhuo Li, Shu Jiang, Zhenxue Jiang, Ming Wen, Chengzao Jia, Yan Song, Weiwei Liu, Yizhou Huang, Xuelian Xie, Tianlin Liu, Pengfei Wang, Chang’an Shan and Yinghui Wu
Minerals 2018, 8(7), 283; https://doi.org/10.3390/min8070283 - 2 Jul 2018
Cited by 38 | Viewed by 3764
Abstract
Organic matter is the material basis of hydrocarbon generation and the abundance of organic matter is a main factor of regional selection and evaluation in shale gas. Also the enrichment is influenced by sedimentary environments. Thus, it is important for the study on [...] Read more.
Organic matter is the material basis of hydrocarbon generation and the abundance of organic matter is a main factor of regional selection and evaluation in shale gas. Also the enrichment is influenced by sedimentary environments. Thus, it is important for the study on the geological factors controlling organic matter enrichment and further to provide scientific basis of regional selection and evaluation by organic matter enrichment area with analysis of the factors. In this paper, the Upper Ordovician–Lower Silurian shale from representative wells in the Upper-Lower Yangtze area is selected as the research object. The goal of this study is to quantitatively calculate the excess siliceous mineral content in shale siliceous minerals and determine the origin of excess silicon based on Al, Fe, and Mn elements; as well as to analyze the sedimentary organic matter enrichment mechanism based on the water body redox environment and bio-productivity. The results show that excess silicon from the Upper Ordovician–Lower Silurian shale in the Upper Yangtze area is biogenic and deposited in closed water bodies. On the one hand, the upper water body contains oxygen, which leads to higher bio-productivity. On the other hand, the lower water body has strong reducibility, which is conducive to sedimentary organic matter preservation. However, the excess silicon in the Upper Ordovician–Lower Silurian shale of the Lower Yangtze area is derived from hydrothermal solution. Hydrothermal activity can enhance the bottom water reducibility, and its nutrient elements can improve bio-productivity and enrich sedimentary organic matter. Therefore, the organic matter enrichment, which depends on the biological productivity and redox conditions, is controlled by the water closure in the Upper Yangtze and hydrothermal activities in the Lower Yangtze respectively. It led to a conclusion that in the process of regional selection and evaluation of shale gas in the Late Ordovician–Early Silurian, it is favorable in the area of relatively strong closure, which is the center of cratonic depression, in the Upper Yangtze and in the hydrotherm-active area, which is the plate connection of the Lower Yangtze and the Cathaysian, in the Lower Yangtze. Full article
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27 pages, 4076 KiB  
Article
Trace Element Partitioning Dualism under Mineral–Fluid Interaction: Origin and Geochemical Significance
by Vladimir L. Tauson, Sergey V. Lipko, Nikolay V. Smagunov and Raisa G. Kravtsova
Minerals 2018, 8(7), 282; https://doi.org/10.3390/min8070282 - 30 Jun 2018
Cited by 24 | Viewed by 4544
Abstract
Trace element (TE) partitioning in the system “mineral-hydrothermal solution” is studied by the method of thermo-gradient crystal growth coupled with internal sampling of a fluid phase. The analytical procedure used enables evaluating of structurally bound and superficially bound modes of TE in crystals [...] Read more.
Trace element (TE) partitioning in the system “mineral-hydrothermal solution” is studied by the method of thermo-gradient crystal growth coupled with internal sampling of a fluid phase. The analytical procedure used enables evaluating of structurally bound and superficially bound modes of TE in crystals and determining corresponding dual partition coefficients. The case of precious metals (PM—Au, Pt, Pd) at 450 and 500 °C and 100 MPa pressure is considered. The minerals are pyrite, As-pyrite, magnetite, Mn-magnetite and hematite and fluids are ammonium chloride-based hydrothermal solutions. The partition coefficients for structural and surficial modes, Dpstr and Dpsur, are found to be unexpectedly high (except for Au in pyrite). High concentrations of PM are attributed to superficial nonautonomous phases (NAPs), which can be considered as primary concentrators of PM. We also have studied the co-crystallization (exchange) coefficients (De) of REE (Ce, Eu, Er, Yb) and Fe in magnetite and hematite at 450 °C and 100 MPa. Desur is elevated to two orders of magnitude as compared to Destr. It is shown that not only physicochemical parameters affect REE distribution in hydrothermal systems, but also NAP presence and its composition. The crystal growth mechanism specified by the agency of NAP is suggested. The study of PM distribution in natural pyrite of gold-ore deposits supported the importance of differentiating between structurally and superficially bound TE modes for correct use of experimental D values to determining element concentrations in ore-forming fluids. Full article
(This article belongs to the Special Issue Experimental and Thermodynamical Modeling of Ore-Forming Processes in Magmatic and Hydrothermal Systems)
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21 pages, 6394 KiB  
Article
Transition from Endothermic to Exothermic Dissolution of Hydroxyapatite Ca5(PO4)3OH–Johnbaumite Ca5(AsO4)3OH Solid Solution Series at Temperatures Ranging from 5 to 65 °C
by Bartosz Puzio, Maciej Manecki and Monika Kwaśniak-Kominek
Minerals 2018, 8(7), 281; https://doi.org/10.3390/min8070281 - 30 Jun 2018
Cited by 17 | Viewed by 5937
Abstract
Five crystalline members of the hydroxyapatite (HAP; Ca5(PO4)3OH)–johnbaumite (JBM; Ca5(AsO4)3OH) series were crystallized at alkaline pH from aqueous solutions and used in dissolution experiments at 5, 25, 45, and 65 °C. [...] Read more.
Five crystalline members of the hydroxyapatite (HAP; Ca5(PO4)3OH)–johnbaumite (JBM; Ca5(AsO4)3OH) series were crystallized at alkaline pH from aqueous solutions and used in dissolution experiments at 5, 25, 45, and 65 °C. Equilibrium was established within three months. Dissolution was slightly incongruent, particularly at the high-P end of the series. For the first time, the Gibbs free energy of formation ΔGf0, enthalpy of formation ΔHf0, entropy of formation Sf0, and specific heat of formation Cpf0 were determined for HAP–JBM solid solution series. Based on the dissolution reaction, Ca5(AsO4)m(PO4)3−mOH = 5Ca2+(aq) + mAsO43−(aq) + (3 − m)PO43−(aq) + OH−(aq), their solubility product Ksp,298.15 was determined. Substitution of arsenic (As) for phosphorus (P) in the structure of apatite resulted in a linear increase in the value of Ksp: from HAP logKsp,298.15 = −57.90 ± 1.57 to JBM logKsp,298.15 = −39.22 ± 0.56. The temperature dependence of dissolution in this solid solution series is very specific; in the temperature range of 5 °C to 65 °C, the enthalpy of dissolution ΔHr varied around 0. For HAP, the dissolution reaction at 5 °C and 25 °C was endothermic, which transitioned at around 40 °C and became exothermic at 45 °C and 65 °C. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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