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Minerals, Volume 9, Issue 8 (August 2019) – 47 articles

Cover Story (view full-size image): Ice, the most abundant mineral in the polar snowpack, is a potential adsorbent for photochemically oxidized Hg (Hg2+) in the atmosphere. As a complement to field and laboratory experiments, the adsorption affinity of Hg2+ for ice surfaces was estimated using ab initio calculations. Results highlighted mild Hg2+ adsorption on ice, which could be the atomic-level cause of the summertime air–snow Hg cycling in the polar regions. View this paper
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Article
Potentially Toxic Elements in Ultramafic Soils: A Study from Metamorphic Ophiolites of the Voltri Massif (Western Alps, Italy)
Minerals 2019, 9(8), 502; https://doi.org/10.3390/min9080502 - 20 Aug 2019
Cited by 7 | Viewed by 1366
Abstract
Ultramafic soils are characterized by severe edaphic conditions induced by a low content of essential nutrients, an adverse Ca/Mg ratio, a low water-holding capacity, and high contents of geogenic potentially toxic elements (PTEs), in particular Cr, Ni, and Co. These metals commonly exceed [...] Read more.
Ultramafic soils are characterized by severe edaphic conditions induced by a low content of essential nutrients, an adverse Ca/Mg ratio, a low water-holding capacity, and high contents of geogenic potentially toxic elements (PTEs), in particular Cr, Ni, and Co. These metals commonly exceed the content limits set by environmental agencies and governments, representing serious environmental risks for ecosystems and human health. In alpine environments, ultramafic soils are characterized by modest thickness and poor horizon differentiation. Several studies on ultramafic soils have shown that their properties may be directly related to the characteristics of the parent rocks, but most of these studies deal with soil chemistry, metal availability, isotopic composition, and pedological characterization. The aim of this research is to investigate how much the geotectonic characteristics of ultramafic bedrocks, such as the degree of serpentinization, metamorphic imprint, and deformation, may affect the mineralogical and chemical variations of ultramafic soils, including the occurrence and potential mobility of the PTEs. Using a multiscale and multi-analytical approach, we fully characterize the properties and mineralogical composition of soil profiles with different ultramafic parent rocks, i.e., partially serpentinized peridotite, massive serpentinites, and foliated serpentinites, sampled within the Voltri Massif High Pressure–Low Temperature (HP–LT) metaophiolite (Western Alps, Italy). Our results, related to soils located at comparable latitude, altitude, landscape position, and pedological environment, outline that the degree of serpentinization, the metamorphic imprint, and the deformation history of the ultramafic parent rocks are key factors influencing soil evolution, mineralogy, and chemistry, as well as PTEs distribution and mobility. Moreover, this study shows that the high content of Cr, Ni, and Co in the studied ultramafic soils has to be considered of geogenic origin and highlights the need for new approaches and methods to obtain indications on the potential contamination of natural or anthropogenic soils. Full article
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Article
Mineralogy and Leachability of Natural Rocks–A Comparison to Electric Arc Furnace Slags
Minerals 2019, 9(8), 501; https://doi.org/10.3390/min9080501 - 20 Aug 2019
Cited by 6 | Viewed by 1768
Abstract
In waste management, recycled and industrial aggregates (e.g., electric arc furnace (EAF) slags) for construction applications have to fulfil the limit values with respect to the total and/or leachable contents of potentially environmentally problematic chemical elements (PEPE, e.g., Cr, Ni, Cu, Mo, V). [...] Read more.
In waste management, recycled and industrial aggregates (e.g., electric arc furnace (EAF) slags) for construction applications have to fulfil the limit values with respect to the total and/or leachable contents of potentially environmentally problematic chemical elements (PEPE, e.g., Cr, Ni, Cu, Mo, V). Natural aggregates, i.e., quarried hard rocks, are neither tested nor regulated for these parameters in most EU member states, e.g., Austria, prior to using them as a construction material. The purpose of this study was to relate the mineralogy to the leachability of natural aggregates with a special emphasis on PEPE and to interpret these findings in comparison with EAF slags. Five samples of Austrian rocks were investigated by polarization microscopy, electron probe microanalyses (EPMA), X-ray diffraction (XRD), and leaching tests as well as by hydrogeochemical modelling using LeachXSTM. Two samples showed elevated total contents of Cr, Ni, and Mo which were present as Cr-spinel, (Fe,Mg)(Al,Cr)2O4, Ni-olivine, (Fe,Mg,Ni)2SiO4, and molybdenite, MoS2. Whereas the former two phases also controlled the leaching of Cr and Ni, the observed leaching of Mo was higher than expected in the case of solubility control by molybdenite. In summary, the leachability of PEPE in natural and industrial aggregates was controlled by similar mineralogical mechanisms. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
A Theoretical Study on the Electronic Structure and Floatability of Rare Earth Elements (La, Ce, Nd and Y) Bearing Fluorapatite
Minerals 2019, 9(8), 500; https://doi.org/10.3390/min9080500 - 20 Aug 2019
Cited by 2 | Viewed by 1245
Abstract
Calcium atoms are often replaced by rare earth elements (REEs) in the lattice of fluorapatite (Ca10F2(PO4)6), making the phosphate ore an important potential rare earth resource. In this paper, the electronic properties of REEs (La, [...] Read more.
Calcium atoms are often replaced by rare earth elements (REEs) in the lattice of fluorapatite (Ca10F2(PO4)6), making the phosphate ore an important potential rare earth resource. In this paper, the electronic properties of REEs (La, Ce, Nd and Y) bearing fluorapatite crystals have been investigated by density functional theory. Results of calculation indicated that the existence of REEs increased the cell parameters of fluorapatite in varying degrees. The REEs substitution made the Fermi level of fluorapatite to move to higher energy levels, making it easier to accept electrons. Except for Y, all the other REEs (La, Ce and Nd) showed that the electronic state mainly exists in the valence band. The Fermi level of REEs were mainly contributed by La5d, Ce4f, Nd4f and Y4d, respectively. The Mulliken values of REE–F and REE–O bonds in REEs-bearing fluorapatites were larger than those of Ca–F and Ca–O bonds in the perfect crystal, and the values of Y–F and Y–O bonds were the largest. The results of interaction between fluorapatite and oleic acid by frontier molecular orbital analysis suggested that the substitution of REEs can improve the reactivity of fluorapatite with oleic acid. Full article
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Review
Tools and Workflows for Grassroots Li–Cs–Ta (LCT) Pegmatite Exploration
Minerals 2019, 9(8), 499; https://doi.org/10.3390/min9080499 - 20 Aug 2019
Cited by 6 | Viewed by 2799
Abstract
The increasing demand for green technology and battery metals necessitates a review of geological exploration techniques for Li–Cs–Ta (LCT) pegmatites, which is applicable to the work of mining companies. This paper reviews the main controls of LCT pegmatite genesis relevant to mineral exploration [...] Read more.
The increasing demand for green technology and battery metals necessitates a review of geological exploration techniques for Li–Cs–Ta (LCT) pegmatites, which is applicable to the work of mining companies. This paper reviews the main controls of LCT pegmatite genesis relevant to mineral exploration programs and presents a workflow of grassroots exploration techniques, supported by examples from central Europe and Africa. Geological exploration commonly begins with information gathering, desktop studies and Geographic Information System (GIS) data reviews. Following the identification of prospective regional areas, initial targets are verified in the field by geological mapping and geochemical sampling. Detailed mineralogical analysis and geochemical sampling of rock, soil and stream sediments represent the most important tools for providing vectors to LCT pegmatites, since the interpretation of mineralogical phases, deportment and liberation characteristics along with geochemical K/Rb, Nb/Ta and Zr/Hf metallogenic markers can detect highly evolved rocks enriched in incompatible elements of economic interest. The importance of JORC (Joint Ore Reserves Committee) 2012 guidelines with regards to obtaining geological, mineralogical and drilling data is discussed and contextualised, with the requirement of treating LCT pegmatites as industrial mineral deposits. Full article
(This article belongs to the Special Issue Novel Methods and Applications for Mineral Exploration)
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Article
Investigation of Spectral Variation of Pine Needles as an Indicator of Arsenic Content in Soils
Minerals 2019, 9(8), 498; https://doi.org/10.3390/min9080498 - 19 Aug 2019
Cited by 2 | Viewed by 1145
Abstract
The spectral response to arsenic (As) stress of pine needles (Pinus densiflora Siebold and Zucc.) from an abandoned lead (Pb)–zinc (Zn) mine was investigated based on chemical and spectroscopic analyses. The correlation analysis between the content of As in needle samples and [...] Read more.
The spectral response to arsenic (As) stress of pine needles (Pinus densiflora Siebold and Zucc.) from an abandoned lead (Pb)–zinc (Zn) mine was investigated based on chemical and spectroscopic analyses. The correlation analysis between the content of As in needle samples and that of soils and spectral parameters of the needle samples were conducted. The results showed very high correlation between As content in pine needles and soils. The major spectral response of pine needles to the As stress were characterized by the increase in the green and red color reflectance, the decrease in the first derivatives at 1648 nm, and the shrink in the red absorption feature. These changes were caused by the pigment content loss and the structural changes of phenolic compounds in the pine needles due to the As content. The linear regression analysis with the stepwise method showed the first derivatives at 668 nm and 1648 nm were the most useful variables in the regression model for As content prediction in pine needles. The As index of pine needles could be used to detect As content in soils associated with As and heavy metals contamination and/or mineralization in coniferous forests. Full article
(This article belongs to the Special Issue Arsenic Geochemistry and Health)
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Review
The Tale of Greenlandite: Commemorating the Two-Hundredth Anniversary of Eudialyte (1819–2019)
Minerals 2019, 9(8), 497; https://doi.org/10.3390/min9080497 - 19 Aug 2019
Cited by 3 | Viewed by 1508
Abstract
Twenty years before the discovery of the mineral eudialyte, a red garnet-like mineral from Greenland was distributed among mineralogists and chemists in Europe. Furthermore, the first chemical analyses of the Greenlandic mineral reported 10 percent by weight of zirconium oxide. It was given [...] Read more.
Twenty years before the discovery of the mineral eudialyte, a red garnet-like mineral from Greenland was distributed among mineralogists and chemists in Europe. Furthermore, the first chemical analyses of the Greenlandic mineral reported 10 percent by weight of zirconium oxide. It was given the name greenlandite, and after the discovery of eudialyte many have wondered whether greenlandite could actually be eudialyte. Two-hundred years after the original definition of eudialyte I have tried to find out. Full article
(This article belongs to the Special Issue Zr-minerals)
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Article
Mineralogical and Environmental Geochemistry of Coal Combustion Products from Shenhuo and Yihua Power Plants in Xinjiang Autonomous Region, Northwest China
Minerals 2019, 9(8), 496; https://doi.org/10.3390/min9080496 - 19 Aug 2019
Cited by 2 | Viewed by 1402
Abstract
The mineralogical and geochemical characteristics of feed coals and coal combustion products (CCPs) from the Shenhuo and Yihua Power Plants in Xinjiang Autonomous Region, were studied by means of proximate analysis, Power X-ray diffraction (XRD), scanning electron microscopy with Energy Dispersive X-ray analyzer [...] Read more.
The mineralogical and geochemical characteristics of feed coals and coal combustion products (CCPs) from the Shenhuo and Yihua Power Plants in Xinjiang Autonomous Region, were studied by means of proximate analysis, Power X-ray diffraction (XRD), scanning electron microscopy with Energy Dispersive X-ray analyzer (SEM-EDX), inductively coupled plasma atomic emission spectrometry (ICP-MS) and inductively coupled plasma mass spectrometry (ICP-AES). The environmental geochemistry of CCPs was evaluated by Al-normalized enrichment factor as well as European Standard EN-12457 leaching test. Two feed coals have the characteristics of low sulfur content, medium to high volatiles matter yields, medium moisture content, super low to medium ash yield, medium to high calorific value and low mineral content. The main crystalline facies in fly ash and slag are quartz and mullite, with a small amount of calcite, and some unburned carbon. Hematite, SrSO4 and barite also can be observed in fly ashes by SEM. Typical plerophere occurs in fine fly ash rather than the coarse fly ash. The concentration of most trace elements in CCPs falls within the lower concentration range of European fly ashes. With respect to the partitioning behavior of trace elements during coal combustion, S is highly volatile, and Mg, Na, Zn, B, Co, As, Nb, Zr, Cu and K also show certain volatility, which may to some extent emit to the atmosphere. Furthermore, leaching experiments show that leachable concentrations of most of the potentially toxic elements in CCPs are low, and the CCPs fall in the range between inert and nonhazardous landfill material regulated by the 2003/33/EC Decision. Full article
(This article belongs to the Collection Minerals in Coal and Coal Combustion Products)
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Article
Multiple Metamorphic Events Recorded within Eclogites of the Chandman District, SW Mongolia
Minerals 2019, 9(8), 495; https://doi.org/10.3390/min9080495 - 18 Aug 2019
Cited by 3 | Viewed by 1556
Abstract
The eclogite-bearing Alag Khadny metamorphic complex in the Lake Zone, SW Mongolia occupies the central region of the Central Asian Orogenic Belt, the largest Phanerozoic orogenic belt in the world. The complex consists mainly of orthogneisses intercalated with eclogites and micaschists in a [...] Read more.
The eclogite-bearing Alag Khadny metamorphic complex in the Lake Zone, SW Mongolia occupies the central region of the Central Asian Orogenic Belt, the largest Phanerozoic orogenic belt in the world. The complex consists mainly of orthogneisses intercalated with eclogites and micaschists in a mélange zone. Most of eclogites are strongly amphibolitized. In this study, we examined petrography and mineral chemistry of eclogites and amphibolitized eclogites, respectively. The result of our research shows that Chandman eclogites experienced multiple events of metamorphism in throughout their subduction and subsequent collision history. We revealed that eclogites were subjected to blueschist facies metamorphism before the peak eclogite facies stage. In addition, we have studied amphibolitized eclogite, and revealed that another distinct progressive medium pressure (MP) epidote-amphibolite facies metamorphic event took place in the eclogite, consistent with collision process. The multiple events of metamorphism in eclogites have been revealed by zonation textures of HP amphiboles zoned with glaucophane→barroisite→Mg-hornblende and MP amphiboles zoned with actinolite/winchite→barroisite→Mg-hornblende/tschermakite/Fe-pargasite. These amphiboles with different zonation textures reflect their metamorphic history of subduction to collision events. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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Article
The Early Silurian Sedimentary Environment of Middle-Upper Yangtze: Lithological and Palaeontological Evidence and Impact on Shale Gas Reservoir
Minerals 2019, 9(8), 494; https://doi.org/10.3390/min9080494 - 18 Aug 2019
Cited by 3 | Viewed by 1099
Abstract
The organic-enriched thick shale at the bottom of Longmaxi Formation is laterally continuous distributed and has been proven to be of good production capability in Fuling of Upper Yangtze. Uplifts that developed during the sedimentation influenced the reservoir characteristics by taking control of [...] Read more.
The organic-enriched thick shale at the bottom of Longmaxi Formation is laterally continuous distributed and has been proven to be of good production capability in Fuling of Upper Yangtze. Uplifts that developed during the sedimentation influenced the reservoir characteristics by taking control of the sedimentary environment and provenance. The sedimentary environments are mainly deep-water shelf, shallow-water shelf, and tidal flat. By analyzing reservoir characteristic of these three environments, the deep-water shelf, which dominated the early stage of sedimentation, formed a high-quality reservoir with high TOC (Total Organic Carbon) content, porosity, and brittleness, while the environment was maintained around the basin centre until the Early Silurian. The shales deposited under the shallow-water environment were of low porosity because of the increasing calcareous and argillaceous contents. Sediments which formed on the tidal flat were arenaceous and of the lowest TOC content as the organic preservation conditions deteriorated. The good correlation of graptolite abundance and TOC content, and high porosity within graptolite fossils emphasize the importance of palaeontological development. The argillaceous cap over the Longmaxi shale is of good sealing capability, and the continuous sedimentation zone along southern Sichuan–eastern Chongqing is the best optimized hydrocarbon-bearing system. However, a weak interface on the discontinuity is the potential lateral pathway for gas diffusion at Northern Guizhou and Western Hunan, but on the southeast margin where the dark shale and the tidal sandstone contact, it promises to form a tight gas reservoir. Full article
(This article belongs to the Special Issue Mineralogy of Shale Gas and Other Low Permeability Reservoirs)
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Article
Melt Inclusions in Plagioclase Macrocrysts at Mount Jourdanne, Southwest Indian Ridge (~64° E): Implications for an Enriched Mantle Source and Shallow Magmatic Processes
Minerals 2019, 9(8), 493; https://doi.org/10.3390/min9080493 - 18 Aug 2019
Cited by 5 | Viewed by 1160
Abstract
Plagioclase ultraphyric basalts (PUBs) with up to 40% millimeter-sized plagioclase crystals, were sampled from the Mount Jourdanne volcanic massif (~64° E) in the Southwest Indian Ridge. The geochemistry of the host glass, the glassy melt inclusions and their host plagioclase macrocrysts (An60-69 [...] Read more.
Plagioclase ultraphyric basalts (PUBs) with up to 40% millimeter-sized plagioclase crystals, were sampled from the Mount Jourdanne volcanic massif (~64° E) in the Southwest Indian Ridge. The geochemistry of the host glass, the glassy melt inclusions and their host plagioclase macrocrysts (An60-69) are used to reveal the mantle heterogeneity and to discuss the origin of Mount Jourdanne PUBs. The melt inclusions trapped in plagioclase display low MgO and high SiO2 contents and show rare earth element (REE) patterns resembling enriched mid-ocean ridge basalts (E-MORB). Together with their positive Sr and Eu anomalies, these features indicate that they were derived from an enriched mantle source, likely a refertilized peridotite or a pyroxenite. In contrast to some 61–67° E basalts, there is a lack of negative Eu anomalies in the PUB host glasses, precluding large amounts of plagioclase crystallization from their parental magma. Petrographic observations and the general chemical similarity between melt inclusions and melts equilibrated with the clinopyroxene cores in regional gabbros and/or troctolites suggest that these plagioclase macrocrysts originate from gabbroic mush within the lower crust. The density contrasts allow the effective segregation of plagioclase prior to their incorporation into the host magma. We propose that these plagioclase macrocrysts were entrained when a new batch of magma passed through the crustal mush zone, and resulted in the formation of the PUB. Eruption of Mount Jourdanne PUBs requires a minimum ascending velocity of 5 m d−1 for the host magma, which is not as high as the eruption rate for typical MORB samples. It is likely that the PUB host magma erupts during a period with reduced magma supply, whereas eruption of aphyric lavas correspond to the fast volcanic formation of the Mount Jourdanne massif. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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Article
Dritsite, Li2Al4(OH)12Cl2·3H2O, a New Gibbsite-Based Hydrotalcite Supergroup Mineral
Minerals 2019, 9(8), 492; https://doi.org/10.3390/min9080492 - 17 Aug 2019
Cited by 5 | Viewed by 1843
Abstract
Dritsite, ideally Li2Al4(OH)12Cl2·3H2O, is a new hydrotalcite supergroup mineral formed as a result of diagenesis in the halite−carnallite rock of the Verkhnekamskoe salt deposit, Perm Krai, Russia. Dritsite forms single lamellar or tabular [...] Read more.
Dritsite, ideally Li2Al4(OH)12Cl2·3H2O, is a new hydrotalcite supergroup mineral formed as a result of diagenesis in the halite−carnallite rock of the Verkhnekamskoe salt deposit, Perm Krai, Russia. Dritsite forms single lamellar or tabular hexagonal crystals up to 0.25 mm across. The mineral is transparent and colourless, with perfect cleavage on {001}. The chemical composition of dritsite (wt. %; by combination of electron microprobe and ICP−MS; H2O calculated by structure refinement) is: Li2O 6.6, Al2O3 45.42, SiO2 0.11, Cl 14.33, SO3 0.21, H2Ocalc. 34.86, O = Cl − 3.24, total 98.29. The empirical formula based on Li + Al + Si = 6 apfu (atom per formula unit) is Li1.99Al4.00Si0.01[(OH)12.19Cl1.82(SO4)0.01]Σ14.02·2.60(H2O). The Raman spectroscopic data indicate the presence of O–H bonding in the mineral, whereas CO32– groups are absent. The crystal structure has been refined in the space group P63/mcm, a = 5.0960(3), c = 15.3578(13) Å, and V = 345.4(5) Å3, to R1 = 0.088 using single-crystal data. The strongest lines of the powder X-ray diffraction pattern (d, Å (I, %) (hkl)) are: 7.68 (100) (002), 4.422 (61) (010), 3.832 (99) (004, 012), 2.561 (30) (006), 2.283 (25) (113), and 1.445 (26) (032). Dritsite was found as 2H polytype, which is isotypic with synthetic material and shows strong similarity to chlormagalumite-2H. The mineral is named in honour of the Russian crystallographer and mineralogist Prof. Victor Anatol`evich Drits. Full article
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Article
Composition of Amphiboles in the Tremolite–Ferro–Actinolite Series by Raman Spectroscopy
Minerals 2019, 9(8), 491; https://doi.org/10.3390/min9080491 - 16 Aug 2019
Cited by 7 | Viewed by 1267
Abstract
Amphiboles are an important family of rock forming minerals, whose identification is crucial in provenance studies as well as in many other fields of geology, archaeology and environmental sciences. This study is aimed to find a quick way to characterize Ca-amphiboles in the [...] Read more.
Amphiboles are an important family of rock forming minerals, whose identification is crucial in provenance studies as well as in many other fields of geology, archaeology and environmental sciences. This study is aimed to find a quick way to characterize Ca-amphiboles in the tremolite (Ca2Mg5Si8O22(OH)2)–ferro–actinolite (Ca2Fe5Si8O22(OH)2) series. Raman spectroscopy is established as technique to perform non-destructive and quick analysis, with micrometric resolution, able to give the composition in terms of Mg/(Mg + Fe2+) ratio. To exploit the method, a preliminary characterization is performed by Scanning Electron Microscopy coupled with Energy-dispersed X-ray Spectroscopy (SEM-EDS). Two independent methods to evaluate the composition from the Raman data (aiming to an accuracy of about 5%), using the low-wavenumbers part of the spectrum and the OH stretching bands, are developed. The application of the proposed method to micro-Raman mappings and the possible use of handheld Raman spectroscopy to have compositional information on Ca-amphiboles are discussed. Full article
(This article belongs to the Special Issue Heavy Minerals: Methods & Case Histories)
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Article
Pyrochlore-Group Minerals in the Granite-Hosted Katugin Rare-Metal Deposit, Transbaikalia, Russia
Minerals 2019, 9(8), 490; https://doi.org/10.3390/min9080490 - 15 Aug 2019
Cited by 2 | Viewed by 1402
Abstract
Pyrochlore group minerals are the main raw phases in granitic rocks of the Katugin complex-ore deposit that stores Nb, Ta, Y, REE, U, Th, Zr, and cryolite. There are three main types: Primary magmatic, early postmagmatic (secondary-I), and late hydrothermal (secondary-II) pyrochlores. The [...] Read more.
Pyrochlore group minerals are the main raw phases in granitic rocks of the Katugin complex-ore deposit that stores Nb, Ta, Y, REE, U, Th, Zr, and cryolite. There are three main types: Primary magmatic, early postmagmatic (secondary-I), and late hydrothermal (secondary-II) pyrochlores. The primary magmatic phase is fluornatropyrochlore, which has high concentrations of Na2O (to 10.5 wt.%), F (to 5.4 wt.%), and REE2O3 (to 17.3 wt.%) but also low CaO (0.6–4.3 wt.%), UO2 (to 2.6 wt.%), ThO2 (to 1.8 wt.%), and PbO (to 1.4 wt.%). Pyrochlore of this type is very rare in nature and is limited to a few occurrences: Rare-metal deposits of Nechalacho in syenite and nepheline syenite (Canada) and Mariupol in nepheline syenite (Ukraine). It may have crystallized synchronously with or slightly later than melanocratic minerals (aegirine, biotite, and arfvedsonite) at the late magmatic stage when Fe from the melt became bound, which hindered the crystallization of columbite. Secondary-I pyrochlore follows cracks or replaces primary pyrochlore in grain rims and is compositionally similar to the early phase, except for lower Na2O concentrations (2.8 wt.%), relatively low F (4 wt.%), and less complete A- and Y-sites occupancy. Secondary-II pyrochlore is a product of late hydrothermal alteration, which postdated the formation of the Katugin deposit. It differs in large ranges of elements and contains minor K, Ba, Pb, Fe, and significant Si concentrations but also low Na and F. Its composition mostly falls within the field of hydro- and keno-pyrochlore. Full article
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
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Article
Mustard Gold of the Gaching Ore Deposit (Maletoyvayam Ore Field, Kamchatka, Russia)
Minerals 2019, 9(8), 489; https://doi.org/10.3390/min9080489 - 15 Aug 2019
Cited by 10 | Viewed by 1429
Abstract
The Gaching high-sulfidation (HS) epithermal Au–Ag deposits, part of the Maletoyvayam ore field, which is located in the volcanic belts of the Kamchatka Peninsula (Russia). The main ore components are native gold, tellurides, selenides, and sulphoselenotellurides of Au and oxidation products of Au-tellurides. [...] Read more.
The Gaching high-sulfidation (HS) epithermal Au–Ag deposits, part of the Maletoyvayam ore field, which is located in the volcanic belts of the Kamchatka Peninsula (Russia). The main ore components are native gold, tellurides, selenides, and sulphoselenotellurides of Au and oxidation products of Au-tellurides. This study examines the different types of native gold in this ore deposit and the mechanisms and sequential transformation of calaverite (AuTe2) into mustard gold. The primary high fineness gold (964‰–978‰) intergrown with maletoyvayamite Au3Te6Se4 and other unnamed phases (AuSe, Au(Te,Se)) differ from the secondary (mustard) gold in terms of fineness (1000‰) and texture. Primary gold is homogeneous, whereas mustard is spongy. Two types of mustard gold were identified: (a) Mixtures of Fe-Sb(Te,Se,S) oxides and fine gold particles, which formed during the hypogenic transformation stage of calaverite due to the impact of hydrothermal fluids, and (b) spotted and colloform gold consisting of aggregates of gold particles in a goethite/hydrogoethite matrix. This formed during the hypergenic transformation stage. Selenides and sulphoselenotellurides of gold did not undergo oxidation. Pseudomorphic replacement of calaverite by Au-Sb(Te,Se,S,As) oxides was also observed. Full article
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Article
Niobium Mineralogy of Pliocene A1-Type Granite of the Carpathian Back-Arc Basin, Central Europe
Minerals 2019, 9(8), 488; https://doi.org/10.3390/min9080488 - 15 Aug 2019
Cited by 4 | Viewed by 1198
Abstract
A1-type granite xenoliths occur in alkali basalts erupted during Pliocene–Pleistocene continental rifting of Carpathian back-arc basin (Central Europe). The Pliocene (5.2 Ma) peraluminous calc-alkalic granite contains unusually high concentrations of critical metals bound in Nb, Ta, REE, U, Th-oxides typical for [...] Read more.
A1-type granite xenoliths occur in alkali basalts erupted during Pliocene–Pleistocene continental rifting of Carpathian back-arc basin (Central Europe). The Pliocene (5.2 Ma) peraluminous calc-alkalic granite contains unusually high concentrations of critical metals bound in Nb, Ta, REE, U, Th-oxides typical for silica-undersaturated alkalic granites, and syenites: columbite-Mn, fergusonite-Y, oxycalciopyrochlore, Nb-rutile, and Ca-niobate (fersmite or viggezite). In contrast, it does not contain allanite and monazite—the main REE-carriers in calc-alkalic granites. The crystallization of REE-bearing Nb-oxides instead of OH-silicates and phosphates was probably caused by strong water deficiency and low phosphorus content in the parental magma. Increased Nb and Ta concentrations have been inherited from the mafic parental magma derived from the metasomatized mantle. The strong Al- and Ca-enrichment probably reflects the specific composition of the mantle wedge modified by fluids, alkalic, and carbonatitic melts liberated from the subducted slab of oceanic crust prior to the Pliocene-Pleistocene rifting. Full article
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
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Review
Removal of Heavy Metals and Metalloids from Water Using Drinking Water Treatment Residuals as Adsorbents: A Review
Minerals 2019, 9(8), 487; https://doi.org/10.3390/min9080487 - 14 Aug 2019
Cited by 33 | Viewed by 2911
Abstract
Heavy metal contamination is one of the most important environmental issues. Therefore, appropriate steps need to be taken to reduce heavy metals and metalloids in water to acceptable levels. Several treatment methods have been developed recently to adsorb these pollutants. This paper reviews [...] Read more.
Heavy metal contamination is one of the most important environmental issues. Therefore, appropriate steps need to be taken to reduce heavy metals and metalloids in water to acceptable levels. Several treatment methods have been developed recently to adsorb these pollutants. This paper reviews the ability of residuals generated as a by-product from the water treatment plants to adsorb heavy metals and metalloids from water. Water treatment residuals have great sorption capacities due to their large specific surface area and chemical composition. Sorption capacity is also affected by sorption conditions. A survey of the literature shows that water treatment residuals may be a suitable material for developing an efficient adsorbent for the removal of heavy metals and metalloids from water. Full article
(This article belongs to the Special Issue Mineral Sorbents)
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Article
Crystal Chemistry and High-Temperature Behaviour of Ammonium Phases NH4MgCl3·6H2O and (NH4)2Fe3+Cl5·H2O from the Burned Dumps of the Chelyabinsk Coal Basin
Minerals 2019, 9(8), 486; https://doi.org/10.3390/min9080486 - 14 Aug 2019
Cited by 5 | Viewed by 1276
Abstract
The technogenic mineral phases NH4MgCl3·6H2O and (NH4)2Fe3+Cl5·H2O from the burned dumps of the Chelyabinsk coal basin have been investigated by single-crystal X-ray diffraction, scanning electron microscopy and [...] Read more.
The technogenic mineral phases NH4MgCl3·6H2O and (NH4)2Fe3+Cl5·H2O from the burned dumps of the Chelyabinsk coal basin have been investigated by single-crystal X-ray diffraction, scanning electron microscopy and high-temperature powder X-ray diffraction. The NH4MgCl3·6H2O phase is monoclinic, space group C2/c, unit cell parameters a = 9.3091(9), b = 9.5353(7), c = 13.2941(12) Å, β = 90.089(8)° and V = 1180.05(18) Å3. The crystal structure of NH4MgCl3·6H2O was refined to R1 = 0.078 (wR2 = 0.185) on the basis of 1678 unique reflections. The (NH4)2Fe3+Cl5·H2O phase is orthorhombic, space group Pnma, unit cell parameters a = 13.725(2), b = 9.9365(16), c = 7.0370(11) Å and V = 959.7(3) Å3. The crystal structure of (NH4)2Fe3+Cl5·H2O was refined to R1 = 0.023 (wR2 = 0.066) on the basis of 2256 unique reflections. NH4MgCl3·6H2O is stable up to 90 °C and then transforms to the less hydrated phase isotypic to β-Rb(MnCl3)(H2O)2 (i.e., NH4MgCl3·2H2O), the latter phase being stable up to 150 °C. (NH4)2Fe3+Cl5·H2O is stable up to 120 °C and then transforms to an X-ray amorphous phase. Hydrogen bonds provide an important linkage between the main structural units and play the key role in determining structural stability and physical properties of the studied phases. The mineral phases NH4MgCl3·6H2O and (NH4)2Fe3+Cl5·H2O are isostructural with natural minerals novograblenovite and kremersite, respectively. Full article
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Article
Geological Mapping and Characterization of Possible Primary Input Materials for the Mineral Sequestration of Carbon Dioxide in Europe
Minerals 2019, 9(8), 485; https://doi.org/10.3390/min9080485 - 13 Aug 2019
Cited by 7 | Viewed by 2191
Abstract
This work investigates the possible mineral input materials for the process of mineral sequestration through the carbonation of magnesium or calcium silicates under high pressure and high temperatures in an autoclave. The choice of input materials that are covered by this study represents [...] Read more.
This work investigates the possible mineral input materials for the process of mineral sequestration through the carbonation of magnesium or calcium silicates under high pressure and high temperatures in an autoclave. The choice of input materials that are covered by this study represents more than 50% of the global peridotite production. Reaction products are amorphous silica and magnesite or calcite, respectively. Potential sources of magnesium silicate containing materials in Europe have been investigated in regards to their availability and capability for the process and their harmlessness concerning asbestos content. Therefore, characterization by X-ray fluorescence (XRF), X-ray diffraction (XRD), and QEMSCAN® was performed to gather information before the selection of specific material for the mineral sequestration. The objective of the following carbonation is the storage of a maximum amount of CO2 and the utilization of products as pozzolanic material or as fillers for the cement industry, which substantially contributes to anthropogenic CO2 emissions. The characterization of the potential mineral resources for mineral sequestration in Europe with a focus on the forsterite content led to a selection of specific input materials for the carbonation tests. The mineralogical analysis of an Italian olivine sample before and after the carbonation process states the reasons for the performed evaluation. The given data serves as an example of the input material suitability of all the collected mineral samples. Additionally, the possible conversion of natural asbestos occurring in minerals as a side effect of the carbonation process is taken into consideration. Full article
(This article belongs to the Special Issue Mineral Deposits of Central Europe)
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Article
Synthesis of Hydroxy-Sodalite/Cancrinite Zeolites from Calcite-Bearing Kaolin for the Removal of Heavy Metal Ions in Aqueous Media
Minerals 2019, 9(8), 484; https://doi.org/10.3390/min9080484 - 13 Aug 2019
Cited by 11 | Viewed by 1619
Abstract
A hydroxy-sodalite/cancrinite zeolite composite was synthesized from low-grade calcite-bearing kaolin by hydrothermal alkali-activation method at 160 °C for 6 h. The effect of calcite addition on the formation of the hydroxy-sodalite/cancrinite composite was investigated using artificial mixtures. The chemical composition and crystal morphology [...] Read more.
A hydroxy-sodalite/cancrinite zeolite composite was synthesized from low-grade calcite-bearing kaolin by hydrothermal alkali-activation method at 160 °C for 6 h. The effect of calcite addition on the formation of the hydroxy-sodalite/cancrinite composite was investigated using artificial mixtures. The chemical composition and crystal morphology of the synthesized zeolite composite were characterized by X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy, and N2 adsorption/desorption analyses. The average specific surface area is around 17–20 m2·g−1, whereas the average pore size lies in the mesoporous range (19–21 nm). The synthesized zeolite composite was used as an adsorbent for the removal of heavy metals in aqueous solutions. Batch experiments were employed to study the influence of adsorbent dosage on heavy metal removal efficiency. Results demonstrate the effective removal of significant quantities of Cu, Pb, Ni, and Zn from aqueous media. A comparative study of synthesized hydroxy-sodalite and hydroxy-sodalite/cancrinite composites revealed the latter was 16–24% more efficient at removing heavy metals from water. The order of metal uptake efficiency for these zeolites was determined to be Pb > Cu > Zn > Ni. These results indicate that zeolite composites synthesized from natural calcite-bearing kaolin materials could represent effective and low-cost adsorbents for heavy metal removal using water treatment devices in regions of water shortage. Full article
(This article belongs to the Special Issue Mineral Sorbents)
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Article
Organo-Modified Vermiculite: Preparation, Characterization, and Sorption of Arsenic Compounds
Minerals 2019, 9(8), 483; https://doi.org/10.3390/min9080483 - 12 Aug 2019
Cited by 8 | Viewed by 1388
Abstract
Among the various technologies tested for removing the anionic species resulting from arsenic contamination, sorption methods have received unflagging interest. Being potential sorbent materials, clay minerals modified by cationic surfactants are often examined for this purpose. Among the clay minerals tested, information regarding [...] Read more.
Among the various technologies tested for removing the anionic species resulting from arsenic contamination, sorption methods have received unflagging interest. Being potential sorbent materials, clay minerals modified by cationic surfactants are often examined for this purpose. Among the clay minerals tested, information regarding sorption properties of expanded vermiculite modified with surfactants is scarce. Therefore, the present study aims to prepare organo-vermiculites modified with hexadecyltrimethylammonium (HDTMA) and benzyldimethylhexadecylammonium (HDBA) at surfactant concentrations of 0.5, 1.0, and 2.0 cation exchange capacity. Modified sorbents were identified and characterized using the analytical methods that can determine phase composition and textural properties of the samples. The sorption of As(III) and As(V) as a function of initial pH value, initial concentration of As(III, V), and initial dosage of sorbent was investigated. The results show that HDTMA and HDBA affect the properties of raw vermiculite. For instance, increase in the concentration of surfactants is often accompanied by a change in interlayer space or textural properties of vermiculite. It was observed that tested organo-minerals adsorbed As(V) to a greater extent compared to As(III). Various analytical studies were carried out and the results revealed the successful synthesis of organo-vermiculite. Moreover, the study also showed that the structure of organo-vermiculite has a significant impact on the uptake of As(III) and As(V) anions. Full article
(This article belongs to the Special Issue Mineral Sorbents)
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Article
Simultaneous Leaching of Seafloor Massive Sulfides and Polymetallic Nodules
Minerals 2019, 9(8), 482; https://doi.org/10.3390/min9080482 - 10 Aug 2019
Cited by 1 | Viewed by 1335
Abstract
Simultaneous leaching of seafloor massive sulfides (SMS) from Loki’s Castle on the Arctic Mid-Ocean Ridge (AMOR) and polymetallic nodules (PN) from Clarion Clipperton Zone (CCZ) of the Central Pacific Ocean was studied. Leaching tests were conducted using sulfuric acid and sodium chloride, at [...] Read more.
Simultaneous leaching of seafloor massive sulfides (SMS) from Loki’s Castle on the Arctic Mid-Ocean Ridge (AMOR) and polymetallic nodules (PN) from Clarion Clipperton Zone (CCZ) of the Central Pacific Ocean was studied. Leaching tests were conducted using sulfuric acid and sodium chloride, at a temperature of 80 °C for 48 h under reflux. The effect of PN-to-SMS ratio was examined. It was shown that simultaneous leaching of two different types of marine resources was possible resulting in high dissolution rates of metals. The proposed process has many advantages as it does not require pyrometallurgical pretreatment, and yields solid products (i.e., silica, barite, elemental sulfur, albite, microcline, muscovite), which might be utilized for various industrial applications. Full article
(This article belongs to the Special Issue Marine Geology and Minerals)
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Article
Reuse of Dunite Mining Waste and Subproducts for the Stabilization of Metal(oid)s in Polluted Soils
Minerals 2019, 9(8), 481; https://doi.org/10.3390/min9080481 - 08 Aug 2019
Cited by 1 | Viewed by 1200
Abstract
The circular economy seeks to minimize the use of raw materials and waste generation. In this context, here we addressed the use of dunite mining tailings and subproducts to stabilize metal(oid)s in polluted soils. We first characterized the dunite mining tailings and subproducts, [...] Read more.
The circular economy seeks to minimize the use of raw materials and waste generation. In this context, here we addressed the use of dunite mining tailings and subproducts to stabilize metal(oid)s in polluted soils. We first characterized the dunite mining tailings and subproducts, and a paradigmatic polluted soil in depth to determine their chemical and mineralogical properties. Experimental trials using Brassica juncea L. were performed to evaluate the impact of the two materials on vegetation growth, edaphic properties and pollutant stabilization yields. To this end, the plants were grown over 75 days in 1 kg pots containing the polluted soil amended with the dunite materials. Notably, both amendments caused a dramatic decrease in the available Zn and a moderate reduction in available Cu, Cd and Pb. In contrast, the concentration of available As was not modified. The cation exchange capacity (CEC) was improved by treatment with the amendments, allowing an increase in the biomass harvested. The immobilization mechanism achieved was probably due to an increase in pH and CEC. In conclusion, the dunite tailings and subproducts could be effective amendments for stabilizing polluted soil. This work paves the way for additional studies with distinct types of soils and conditions. Full article
(This article belongs to the Special Issue Application of Mineral-Based Amendments)
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Article
Mineral Precipitation in Fractures and Nanopores within Shale Imaged Using Time-Lapse X-ray Tomography
Minerals 2019, 9(8), 480; https://doi.org/10.3390/min9080480 - 07 Aug 2019
Cited by 3 | Viewed by 1600
Abstract
Barite precipitation in fractures and nanopores within a shale sample is analysed in situ, in 3D, and over time. Diffusion of barium and sulphate from opposite sides of the sample creates a supersaturated zone where barium sulphate crystals precipitate. Time-lapse synchrotron-based computed tomography [...] Read more.
Barite precipitation in fractures and nanopores within a shale sample is analysed in situ, in 3D, and over time. Diffusion of barium and sulphate from opposite sides of the sample creates a supersaturated zone where barium sulphate crystals precipitate. Time-lapse synchrotron-based computed tomography was used to track the growth of precipitates over time, even within the shale’s matrix where the nanopores are much smaller than the resolution of the technique. We observed that the kinetics of precipitation is limited by the type and size of the confinement where crystals are growing, i.e., nanopores and fractures. This has a major impact on the ion transport at the growth front, which determines the extent of precipitation within wider fractures (fast and localised precipitation), thinner fractures (non-localised and slowing precipitation) and nanopores (precipitation spread as a front moving at an approximately constant velocity of 10 ± 3 µm/h). A general sequence of events during precipitation in rocks containing pores and fractures of different sizes is proposed and its possible implications to earth sciences and subsurface engineering, e.g., fracking and mineral sequestration, are discussed. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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Article
Re Sulfides from Zhelos and Tokty-Oi Intrusions (East Sayan, Russia)
Minerals 2019, 9(8), 479; https://doi.org/10.3390/min9080479 - 07 Aug 2019
Cited by 2 | Viewed by 1177
Abstract
Re sulfides were discovered in Cu–Ni–platinum-group elements (PGE) ores of the Zhelos and Tokty-Oi intrusions. These intrusions can be considered as products of the mantle superplume responsible for Rodinia’s break-up. The mineral compositions were determined in situ in polished samples. Electron microprobe analyses [...] Read more.
Re sulfides were discovered in Cu–Ni–platinum-group elements (PGE) ores of the Zhelos and Tokty-Oi intrusions. These intrusions can be considered as products of the mantle superplume responsible for Rodinia’s break-up. The mineral compositions were determined in situ in polished samples. Electron microprobe analyses were mostly consistent with a general formula of (Cu,Fe,Mo,Os,Re)5S8, (Cu,Fe,Mo,Os,Re)4S7, and (Cu,Fe,Mo,Re)S2. One of the major features of Re sulfide from the Zhelos intrusion is its high osmium content. The ΣMe/S ratio for a part of our data is consistent with that of the tarkianite. Re sulfides from the Tokty-Oi have a ΣMe/S ratio similar to those in rheniite or dzeskazganite, but differ from them by the presence of Fe and Cu and the metal-to-metal ratio. The localization of the Re sulfide within the chalcopyrite suggests its crystallization from the residual Cu-rich liquid. Full article
(This article belongs to the Special Issue Sulfide Geochemistry)
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Article
Geology, Fluid Inclusions and Stable Isotopes of the Xialiugou Polymetallic Deposit in North Qilian, Northwest China: Constraints on its Metallogenesis
Minerals 2019, 9(8), 478; https://doi.org/10.3390/min9080478 - 07 Aug 2019
Viewed by 1287
Abstract
The Xialiugou polymetallic deposit is located in the North Qilian Orogenic Belt, Northwest China, of which the main ore-bearing strata are the Middle Cambrian Heicigou Group. The mineralization is zoned with “black” orebodies (galena–sphalerite), which are stratigraphically above the “yellow” orebodies (pyrite–chalcopyrite–tennantite) at [...] Read more.
The Xialiugou polymetallic deposit is located in the North Qilian Orogenic Belt, Northwest China, of which the main ore-bearing strata are the Middle Cambrian Heicigou Group. The mineralization is zoned with “black” orebodies (galena–sphalerite), which are stratigraphically above the “yellow” orebodies (pyrite–chalcopyrite–tennantite) at the lower zone, corresponding to the alteration assemblages of quartz–sericite in the ore-proximal zone and chlorite in the ore-distal zone. The Xialiugou mineralization can be divided into three stages: (1) Stage I (pyrite); (2) Stage II (chalcopyrite–tennantite–sphalerite); and (3) Stage III (galena–sphalerite). Fluid inclusions data indicate that the physicochemical conditions that lead to ore formation were the medium–low temperature (157–350 °C) and low salinity (0.17–6.87 wt % NaCleqv), and that the ore-forming temperature tended to decrease with the successive mineralization processes. Taking the H–O isotopic compositions (δDV-SMOW = −51.0‰ to −40.5‰, δ18OH2O = −0.4‰ to 8.6‰) into consideration, the ore-forming fluids were most likely derived from seawater with a small amount of magmatic- and meteoric-fluids input. In addition, the combined S (−3.70‰ to 0.10‰) and Pb isotopic (206Pb/204Pb = 18.357 to 18.422, 207Pb/204Pb = 15.615 to 15.687, 208Pb/204Pb = 38.056 to 38.248) data of pyrite indicate that the ore-bearing volcanic rocks may be an important source of ore-forming materials. Finally, we inferred that the Xialiugou deposit shares similarities with the most important volcanogenic massive sulfide (VMS) deposits (Baiyinchang ore field) in China and typical “black ore” type VMS deposits worldwide. Full article
(This article belongs to the Special Issue Massive Sulfide Deposits all around the World)
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Article
Rare Earth Element Recovery from Acidic Extracts of Florida Phosphate Mining Materials Using Chelating Polymer 1-Octadecene, Polymer with 2,5-Furandione, Sodium Salt
Minerals 2019, 9(8), 477; https://doi.org/10.3390/min9080477 - 06 Aug 2019
Cited by 5 | Viewed by 1752
Abstract
To meet the growing global demand for rare earth elements (REEs), nontraditional mining sources of these metals are being investigated. Phosphate ore and phosphate mining wastes have been identified as possible alternative sources to REEs. In this study, REEs were extracted from Florida [...] Read more.
To meet the growing global demand for rare earth elements (REEs), nontraditional mining sources of these metals are being investigated. Phosphate ore and phosphate mining wastes have been identified as possible alternative sources to REEs. In this study, REEs were extracted from Florida phosphate mining materials using mineral and organic acids. The REEs were then recovered at high efficiencies using a chelating polymer, 1-octadecene, polymer with 2,5-furandione, sodium salt. At pH 1.5, the chelation polymer effectively bound nearly 100% of the rare earth elements extracted from the solids. Overall extraction and recovery yields were between 80% for gadolinium and 8% for praseodymium from amine tailings, between 70% for terbium and 7% for praseodymium from phosphogypsum, between 56% for scandium and 15% for praseodymium from phosphate rock, and between 77% for samarium and 31% for praseodymium from waste clay. These results suggest that this chelating polymer efficiently recovers rare earth elements from acidic extracts of phosphate mining waste products. Full article
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Article
Zircon U-Pb, Molybdenite Re-Os and Quartz Vein Rb-Sr Geochronology of the Luobuzhen Au-Ag and Hongshan Cu Deposits, Tibet, China: Implications for the Oligocene-Miocene Porphyry–Epithermal Metallogenic System
Minerals 2019, 9(8), 476; https://doi.org/10.3390/min9080476 - 04 Aug 2019
Cited by 5 | Viewed by 1072
Abstract
The Gangdese metallogenic belt in Tibet is an important copper and iron polymetallic, metallogenic belt in western China. The Luobuzhen epithermal Au-Ag and Hongshan porphyry Cu deposits, as two new discovery deposits in the last few years, are located in the western Gangdese [...] Read more.
The Gangdese metallogenic belt in Tibet is an important copper and iron polymetallic, metallogenic belt in western China. The Luobuzhen epithermal Au-Ag and Hongshan porphyry Cu deposits, as two new discovery deposits in the last few years, are located in the western Gangdese metallogenic belt. In this paper, we present quartz vein Rb-Sr isochron, zircon U-Pb and molybdenite Re-Os ages for a better understanding of the minerallogenetic epoch of the deposits. Geochronological data show that the Rb-Sr isochron age of a quartz vein in a Luobuzhen Au-Ag deposit is 21.1 ± 1.8 Ma (MSWD (mean standard weighted deviation) = 0.19), zircon U-Pb ages from diorite and granodiorite porphyry in Hongshan Cu deposit are 50.0 ± 0.4 Ma (MSWD = 0.94) and 23.7 ± 0.1 Ma (MSWD = 0.73), respectively, and a Re-Os isochron age of molybdenite in Hongshan Cu deposit is 23.0 ± 2.0 Ma (MSWD = 0.014). These data suggest that the Luobuzhen epithermal Au-Ag and Hongshan porphyry Cu deposits formed at ca. 23–21 Ma, which were controlled by the same magmatic hydrothermal events. Formation of both the Luobuzhen and Hongshan deposits were obviously earlier than the Miocene porphyry metallogenetic events in the Gangdese porphyry copper belt. Full article
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Article
Formation of the Granodiorite-Hosting Magushan Cu–Mo Polymetallic Deposit in Southern Anhui, Eastern China: Evidences from Geochronology and Geochemistry
Minerals 2019, 9(8), 475; https://doi.org/10.3390/min9080475 - 02 Aug 2019
Cited by 9 | Viewed by 1158
Abstract
The newly discovered Magushan Cu-Mo polymetallic deposit, located in southeastern Anhui, eastern China, is a middle-scale skarn-type polymetallic deposit with different ore types of veinlets-disseminated skarn (the primary type), quartz veins, and porphyry. LA-ICP-MS zircon U–Pb analyses yielded a crystallization age of 135.7 [...] Read more.
The newly discovered Magushan Cu-Mo polymetallic deposit, located in southeastern Anhui, eastern China, is a middle-scale skarn-type polymetallic deposit with different ore types of veinlets-disseminated skarn (the primary type), quartz veins, and porphyry. LA-ICP-MS zircon U–Pb analyses yielded a crystallization age of 135.7 ± 1.5 Ma for the ore-related granodiorite in Magushan. The granodiorites are I-type granites in nature, characterized by metaluminous and high-K calc-alkaline characteristics. They are enriched in large ion lithophile elements (LILEs, e.g., Ba, Th, and U) and light rare earth elements (LREEs), and depleted in high field strength elements (NFSEs, e.g., Nb, Ta, and Ti) and heavy rare earth element (HREEs), with slightly negative Eu anomalies (Eu/Eu* = 0.81–0.86). These granodiorites show high Mg# (mainly > 40) values, high MgO (1.73–1.96 wt. %) and low Na2O (<4.21 wt. %) contents, with whole-rock (87Sr/86Sr)i ratios (0.708877 to 0.710398), negative εNd(t) values of −5.4 to −5.2, and negative zircon εHf(t) values of −4.60 to −1.37, with old two-stage Hf model ages (TDM2) between 1.2‒1.5 Ga. Besides, they are characterized by high radiogenic Pb isotopic compositions with (206Pb/204Pb)i = 18.44–18.56, (207Pb/204Pb)i = 15.66–15.67, and (208Pb/204Pb)i = 38.77–38.87. These granodiorites are characterized by high zircon Ce4+/Ce3+ ratios (average 893) and Eu/Eu* ratios (average 0.51), indicating high magmatic oxygen fugacities. The distinct geochemical and isotopic features suggest that the Magushan granodiorites could be formed by metasomatized mantle-derived magmas, mixing with materials from Neoproterozoic crust that is widely distributed in the Southern Anhui. This study concludes that the formation of the Magushan Cu-Mo polymetallic deposits may largely depend on an oxidizing environment and multi-sources mixed of mantle- and crust-derived materials. Full article
(This article belongs to the Special Issue Role of Magmatic Activity in Generation of Ore Deposits)
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Article
Processes and Conditions of the Origin for Fe3+-Bearing Magnesiowüstite under Lithospheric Mantle Pressures and Temperatures
Minerals 2019, 9(8), 474; https://doi.org/10.3390/min9080474 - 01 Aug 2019
Cited by 2 | Viewed by 1219
Abstract
An experimental study, implicated in the revealing of the conditions for the origin for Fe3+-bearing magnesiowüstite in the lithospheric mantle, was performed using Mössbauer spectroscopy of pre-synthesized samples. Experiments were carried out using a multi-anvil high-pressure split-sphere apparatus at 6.3–7.5 GPa, [...] Read more.
An experimental study, implicated in the revealing of the conditions for the origin for Fe3+-bearing magnesiowüstite in the lithospheric mantle, was performed using Mössbauer spectroscopy of pre-synthesized samples. Experiments were carried out using a multi-anvil high-pressure split-sphere apparatus at 6.3–7.5 GPa, in the range of 1100–1650 °C in carbonate-metal, carbonate–oxide-metal, carbonate-oxide, carbide-oxide and carbonate–metal- sulphur systems. In three experimental series, oxygen fugacity gradient in the samples was created, which enabled the study of the processes of magnesiowüstite formation under oxidizing and reducing conditions (ΔlogfO2 (FMQ) values from −1 to −5). It was established that Fe3+-bearing magnesiowüstite can form both in assemblage with oxidized phases, such as carbonate or with reduced ones—metal, carbides, sulphides, graphite and diamond. According to the Mössbauer spectroscopy, the composition of synthesized magnesiowüstite varied within a range of Fe3+/ΣFe values from 0 to 0.3, with IV and VI coordination of Fe3+ depending on P, T, fO2, x-parameters. It was established that Fe3+-bearing magnesiowüstite formation processes under upper mantle P,T-conditions include redox reactions, with magnesiowüstite being (1) reductant or (2) product of interaction, (3) crystallization processes of magnesiowüstite from an oxidized melt, where magnesiowüstite acts as a sink for ferric iron and (4) iron disproportionation. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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Article
Comparative Studies of Quaternary Ammonium Salts on the Aggregation and Dispersion Behavior of Kaolinite and Quartz
Minerals 2019, 9(8), 473; https://doi.org/10.3390/min9080473 - 31 Jul 2019
Cited by 1 | Viewed by 1109
Abstract
Fine particles in the presence of flotation reagents exhibit different dispersion and aggregation behaviors in a mineral suspension, and affect the flotation separation processes. In this study, the effects of three quaternary ammonium salts (i.e., dodecyltrimethylammonium chloride (DTAC), tetradecyltrimethylammonium chloride (TTAC), and hexadecyltrimethylammonium [...] Read more.
Fine particles in the presence of flotation reagents exhibit different dispersion and aggregation behaviors in a mineral suspension, and affect the flotation separation processes. In this study, the effects of three quaternary ammonium salts (i.e., dodecyltrimethylammonium chloride (DTAC), tetradecyltrimethylammonium chloride (TTAC), and hexadecyltrimethylammonium chloride (CTAC)) on the dispersion and aggregation behaviors of kaolinite and quartz were studied. The mechanism was systematically investigated using sedimentation tests, reagent adsorption analysis, zeta potential measurements, and SEM analysis. In the absence of reagents, the kaolinite and quartz particles exhibited good aggregation behaviors at acid and neutral pHs compared with alkaline conditions. Except for CTAC, the presence of DTAC and TTAC improved the aggregation behavior of both minerals in neutral and alkaline conditions. More, the sedimentation yields of both minerals were increased significantly with increasing the concentration of DTAC and TTAC. However, the increasing concentration of CTAC resulted in an increase in the dispersion of kaolinite and quartz particles under the same conditions. At neutral and alkaline conditions, the zeta potentials and adsorbed amounts of all three salts on the mineral surfaces were increased significantly with increasing the concentrations of salts, and the adsorbed amount adopted the following sequence: CTAC > TTAC > DTAC. The zeta potential results showed that the stronger adsorption of quaternary ammonium salts on mineral surfaces at neutral and alkaline conditions was mainly because of electrostatic interactions. Full article
(This article belongs to the Special Issue Flotation Reagents)
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