Minerals

18 pages, 2385 KiB

Open AccessEditor’s ChoiceArticle

The Behaviour of Rare Earth Elements from South African Coal Fly Ash during Enrichment Processes: Wet, Magnetic Separation and Zeolitisation

by Mero-Lee Ursula Cornelius, Alechine Emmanuel Ameh, Chuks Paul Eze, Olanrewaju Fatoba, Asel Sartbaeva and Leslie Felicia Petrik

Minerals 2021, 11(9), 950; https://doi.org/10.3390/min11090950 - 31 Aug 2021

Cited by 18 | Viewed by 5494

Abstract

Rare earth elements (REEs) are essential raw materials in a variety of industries including clean energy technologies such as electric vehicles and wind turbines. This places an ever-increasing demand on global rare earth element production. Coal fly ash (CFA) possesses appreciable levels of [...] Read more.

Rare earth elements (REEs) are essential raw materials in a variety of industries including clean energy technologies such as electric vehicles and wind turbines. This places an ever-increasing demand on global rare earth element production. Coal fly ash (CFA) possesses appreciable levels of REEs. CFA, a waste by-product of coal combustion, is therefore a readily available source of REEs that does not require mining. CFA valorisation to zeolites has been achieved via various synthesis pathways. This study aimed to evaluate one such pathway by monitoring how REEs partition during CFA processing by the wet, magnetic separation process and zeolitisation. South African CFA was subjected to wet, magnetic separation and subsequent zeolitisation of the nonmagnetic fraction (NMF); solid products were characterised by XRD, SEM, XRF and LA-ICP-MS. The wet, magnetic separation process resulted in the partitioning of a specific set of transition metals (such as Fe, Mn, Cr, V, Ni, Zn, Cu, Co and Mo) into the magnetic fraction (MF) of CFA, while REEs partitioned into the NMF with a total REE content of 530.2 ppm; thus, the matrix elements of CFA were extracted with ease. Zeolitisation resulted in a solid zeolite product (hydroxysodalite) with a total REE content of 537.6 ppm. The process of zeolitisation also resulted in the selective enrichment of Ce (259.1 ppm) into the solid zeolite product (hydroxysodalite), while other REEs were largely partitioned into the liquid phase. CFA valorisation by wet, magnetic separation and zeolitisation therefore allowed for the partitioning of REEs into various extraction products while recovering the matrix elements of CFA such as Fe, Si and Al. The findings of this study highlight the geopolitical importance of REEs in terms of the development of alternative processes for REE recovery from waste and alternative sources, which may potentially give countries that employ and develop the technology a key advantage in the production of REEs for the global market. Full article

(This article belongs to the Special Issue Recovery of Precious Metals, Rare Earth Elements and Special Metals from Spent Secondary Products)

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24 pages, 3541 KiB

Open AccessEditor’s ChoiceReview

Geochemical Occurrence of Rare Earth Elements in Mining Waste and Mine Water: A Review

by Konstantina Pyrgaki, Vasiliki Gemeni, Christos Karkalis, Nikolaos Koukouzas, Petros Koutsovitis and Petros Petrounias

Minerals 2021, 11(8), 860; https://doi.org/10.3390/min11080860 - 10 Aug 2021

Cited by 29 | Viewed by 7180

Abstract

Μining waste, processing by-products and mine water discharges pose a serious threat to the environment as in many cases they contain high concentrations of toxic substances. However, they may also be valuable resources. The main target of the current review is the comparative [...] Read more.

Μining waste, processing by-products and mine water discharges pose a serious threat to the environment as in many cases they contain high concentrations of toxic substances. However, they may also be valuable resources. The main target of the current review is the comparative study of the occurrence of rare earth elements (REE) in mining waste and mine water discharges produced from the exploitation of coal, bauxite, phosphate rock and other ore deposits. Coal combustion ashes, bauxite residue and phosphogypsum present high percentages of critical REEs (up to 41% of the total REE content) with ΣREY content ranging from 77 to 1957.7 ppm. The total REE concentrations in mine discharges from different coal and ore mining areas around the globe are also characterised by a high range of concentrations from 0.25 to 9.8 ppm and from 1.6 to 24.8 ppm, respectively. Acid mine discharges and their associated natural and treatment precipitates seem to be also promising sources of REE if their extraction is coupled with the simultaneous removal of toxic pollutants. Full article

(This article belongs to the Special Issue Understanding Geochemical Processes Using Rare Earth Element Content of Natural and Anthropogenic Materials)

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15 pages, 3387 KiB

Open AccessEditor’s ChoiceArticle

The Temperature of Halite Crystallization in the Badenian Saline Basins, in the Context of Paleoclimate Reconstruction of the Carpathian Area

by Anatoliy R. Galamay, Krzysztof Bukowski, Igor M. Zinchuk and Fanwei Meng

Minerals 2021, 11(8), 831; https://doi.org/10.3390/min11080831 - 30 Jul 2021

Cited by 7 | Viewed by 3315

Abstract

Currently, fluid inclusions in halite have been frequently studied for the purpose of paleoclimate reconstruction. For example, to determine the air temperature in the Middle Miocene (Badenian), we examine single-phase primary fluid inclusions of the bottom halites (chevron and full-faceted) and near-surface (cumulate) [...] Read more.

Currently, fluid inclusions in halite have been frequently studied for the purpose of paleoclimate reconstruction. For example, to determine the air temperature in the Middle Miocene (Badenian), we examine single-phase primary fluid inclusions of the bottom halites (chevron and full-faceted) and near-surface (cumulate) halites collected from the salt-bearing deposits of the Carpathian region. Our analyses showed that the temperatures of near-bottom brines varied in ranges from 19.5 to 22.0 °C and 24.0 to 26.0 °C, while the temperatures of the surface brines ranged from 34.0 to 36.0 °C. Based on these data, such as an earlier study of lithology and sedimentary structures of the Badenian rock salts, the crystallization of bottom halite developed in the basin from concentrated and cooled near-surface brines of about 30 m depth. Our results comply with the data on the temperature distribution in the modern Dead Sea. Full article

(This article belongs to the Special Issue Mineralogy, Petrology and Geochemistry of Evaporites)

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21 pages, 7628 KiB

Open AccessEditor’s ChoiceArticle

Investigation of Lateral Confinement, Roller Aspect Ratio and Wear Condition on HPGR Performance Using DEM-MBD-PRM Simulations

by Victor Alfonso Rodriguez, Gabriel K. P. Barrios, Gilvandro Bueno and Luís Marcelo Tavares

Minerals 2021, 11(8), 801; https://doi.org/10.3390/min11080801 - 23 Jul 2021

Cited by 28 | Viewed by 3872

Abstract

It has been known that the performance of high-pressure grinding rolls (HPGR) varies as a function of the method used to laterally confine the rolls, their diameter/length (aspect) ratio as well as their condition, if new or worn. However, quantifying these effects through [...] Read more.

It has been known that the performance of high-pressure grinding rolls (HPGR) varies as a function of the method used to laterally confine the rolls, their diameter/length (aspect) ratio as well as their condition, if new or worn. However, quantifying these effects through direct experimentation in machines with reasonably large dimensions is not straightforward, given the challenge, among others, of guaranteeing that the feed material remains unchanged. The present work couples the discrete element method (DEM) to multibody dynamics (MBD) and a novel particle replacement model (PRM) to simulate the performance of a pilot-scale HPGR grinding pellet feed. It shows that rotating side plates, in particular when fitted with studs, will result in more uniform forces along the bed, which also translates in a more constant product size along the rolls as well as higher throughput. It also shows that the edge effect is not affected by roll length, leading to substantially larger proportional edge regions for high-aspect ratio rolls. On the other hand, the product from the center region of such rolls was found to be finer when pressed at identical specific forces. Finally, rolls were found to have higher throughput, but generate a coarser product when worn following the commonly observed trapezoidal profile. The approach often used in industry to compensate for roller wear is to increase the specific force and roll speed. It has been demonstrated to be effective in maintaining product fineness and throughput, as long as the minimum safety gap is not reached. Full article

(This article belongs to the Special Issue Simulation Using the Discrete Element Method (DEM) in the Minerals Industry)

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21 pages, 4528 KiB

Open AccessEditor’s ChoiceArticle

Organic and Isotopic Geochemistry of Evaporites and Shales of the Santana Group (Araripe Basin, Brazil): Clues on the Evolution of Depositional Systems and Global Correlation during the Lower Cretaceous

by Naedja Vasconcelos Pontes, Daniel Bezerra das Chagas, Ana Clara Braga de Souza, Daniel Rodrigues do Nascimento Junior, Wellington Ferreira da Silva Filho, Ramsés Capilla, Antônio Jorge Vasconcellos Garcia and José de Araújo Nogueira Neto

Minerals 2021, 11(8), 795; https://doi.org/10.3390/min11080795 - 22 Jul 2021

Cited by 12 | Viewed by 4437

Abstract

Even being the more studied of the interior basins of Northeast Brazil, the Araripe Basin still lacks research in organic geochemistry designed to support interpretations of depositional systems and conditions of formation. This work aims to investigate the organic behavior of evaporites and [...] Read more.

Even being the more studied of the interior basins of Northeast Brazil, the Araripe Basin still lacks research in organic geochemistry designed to support interpretations of depositional systems and conditions of formation. This work aims to investigate the organic behavior of evaporites and shales from the Santana Group (Lower Cretaceous), as well as discuss their role in the evolution of its depositional systems. A total of 23 samples, 17 shales and six evaporites, were collected in outcrops and quarries. Analyses of Total Organic Carbon (TOC), Total Sulfur (TS), Rock Eval pyrolysis, and the δ³⁴S isotope ratio were performed. The TOC results revealed high organic content for seven intervals, of which only five had high TS content. From the Rock Eval pyrolysis, dominance of the Type I kerogen was verified, thus corresponding to the best type of organic matter (mainly algal) for the generation of liquid and gaseous hydrocarbons. The Lower Cretaceous (probably Aptian) response to the progressive evolution in redox conditions is linked to a remarked Oceanic Anoxic Event (OAE-1a). The TOC/TS ratio suggests variable palaeosalinity, indicating most of the shales were formed under brackish waters with saline influence, yet tending to increase the salinity upwards where hypersaline conditions dominate in the Ipubi Formation. The isotope data also suggest the occurrence of marine ingressions in the depositional systems even prior to the well-documented event of the Romualdo Formation. Full article

(This article belongs to the Special Issue Mineralogy, Petrology and Geochemistry of Evaporites)

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19 pages, 8239 KiB

Open AccessEditor’s ChoiceArticle

Freeze–Thaw Damage Model of Polypropylene Fiber Reinforced Cement Stabilized Waste Construction Slurry under Uniaxial Action

by Ping Jiang, Lin Zhou, Yue Wang, Biao Qian, Wei Wang, Na Li and Fang Zhang

Minerals 2021, 11(7), 743; https://doi.org/10.3390/min11070743 - 8 Jul 2021

Cited by 12 | Viewed by 2270

Abstract

In order to apply the fiber reinforced cement stabilized waste construction slurry more widely, it is crucial to evaluate its mechanical behavior under freeze and thaw (F–T) cycles. The mechanical properties of fiber cement-modified waste construction slurry (FCMS) under five different F–T cycles [...] Read more.

In order to apply the fiber reinforced cement stabilized waste construction slurry more widely, it is crucial to evaluate its mechanical behavior under freeze and thaw (F–T) cycles. The mechanical properties of fiber cement-modified waste construction slurry (FCMS) under five different F–T cycles were studied using unconfined compressive strength tests. One fixed cement sample with five different types of polypropylene fiber was used in the FCMS. Using the meso random damage model, the two-stage damage stress–strain relationship of FCMS was established using particle swarm optimization (PSO). The results were as follows: (1) The mechanical properties of FCMS at room temperature and in an F–T environment were significantly improved by fiber; (2) The elastic modulus of FCMS decreased in the form of a power function with the increase of F–T cycles; (3) The fitting results of the two-stage F–T damage model based on meso random damage theory were in agreement with the measured data. Full article

(This article belongs to the Special Issue Alkali-Activated Cements and Concretes)

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15 pages, 39831 KiB

Open AccessEditor’s ChoiceArticle

Creation of Backfill Materials Based on Industrial Waste

by Jarosław Rybak, Cheynesh Kongar-Syuryun, Yulia Tyulyaeva and Albert M. Khayrutdinov

Minerals 2021, 11(7), 739; https://doi.org/10.3390/min11070739 - 7 Jul 2021

Cited by 33 | Viewed by 4544

Abstract

The possibility of replacing the traditional components of the filling mass with man-made waste and the need for the use of mechanical activation of the components of the filling composite in order to improve its rheological characteristics and the strength of the mass [...] Read more.

The possibility of replacing the traditional components of the filling mass with man-made waste and the need for the use of mechanical activation of the components of the filling composite in order to improve its rheological characteristics and the strength of the mass after solidification are proved. The demand for resource-reproducing technologies that allow the most complete use of the industrial mineral resource potential of the mining and processing enterprise, which will lead to a multiplicative ecological and economic effect, is confirmed. It is necessary to introduce the re-processing of man-made waste in order to further extract the useful component to a level that meets the standards of environmental safety and economic feasibility, which would create conditions for the actual sustainable development and give some perspectives for extending the operating time of mining regions. It is established that the sustainable development of the mining and processing region is impossible without a highly efficient exploitation of natural deposits and man-made georesources in combination with an integrated approach to the development of subsurface resources. Full article

(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)

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17 pages, 6192 KiB

Open AccessEditor’s ChoiceArticle

Tracking and Evaluating the Concentrations of Natural Radioactivity According to Chemical Composition in the Precambrian and Mesozoic Granitic Rocks in the Jangsu-gun Area, Central Southwestern South Korea

by Sung Won Kim, Weon-Seo Kee, Saro Lee, Byung Choon Lee and Uk Hwan Byun

Minerals 2021, 11(7), 684; https://doi.org/10.3390/min11070684 - 25 Jun 2021

Cited by 3 | Viewed by 3229

Abstract

The Jangsu-gun area in the central Southwestern South Korea consists of a well-preserved Middle Paleoproterozoic gneissic basement, as well as the Late Triassic and Early Jurassic granitic rocks. Here, we present the detailed zircon U-Pb age data and whole-rock chemical compositions, including radioactive [...] Read more.

The Jangsu-gun area in the central Southwestern South Korea consists of a well-preserved Middle Paleoproterozoic gneissic basement, as well as the Late Triassic and Early Jurassic granitic rocks. Here, we present the detailed zircon U-Pb age data and whole-rock chemical compositions, including radioactive elements (e.g., U and Th) and activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K for the Middle Paleoproterozoic gneisses, and Late Triassic and Early Jurassic granitic rocks of the Jangsu-gun area. The Middle Paleoproterozoic gneissic basement, and the Late Triassic and Early Jurassic granitic rocks have ages of ca. 1988 Ma and 1824 Ma, 230 Ma and 187–189 Ma, respectively. Geochemically, the Middle Paleoproterozoic orthogneiss, Late Triassic granites and Early Jurassic granitic rocks show typical arc-related metaluminous to weakly peraluminous fractionated granite features with ASI (aluminum saturation index) values of 0.92 to 1.40. The mean values of U (ppm) and Th (ppm) of the Middle Paleoproterozoic orthogneisses (6.4 and 20.5, respectively), Late Triassic granites (1.5 and 10.9), and Early Jurassic granites (3.5 and 16.5) were similar to those (5 and 15) of the granitic rocks in the Earth’s crust. The mean ²²⁶Ra (Bq/kg), ²³²Th (Bq/kg), and ⁴⁰K (Bq/kg) activity concentrations and radioactivity concentration index (RCI) are 62, 71, 1,214 and 0.96 for the Middle Paleoproterozoic orthogneisses; 16, 39, 1,614 and 0.78 for the Late Triassic granites; and 56, 70, 1031 and 0.88 for the Early Jurassic granitic rocks, respectively. The U, Th, ²²⁶Ra, ²³²Th, ⁴⁰K, and RCI of the Middle Paleoproterozoic biotite paragneisses are similar to those of the Middle Paleoproterozoic orthogneisses. The trend of ²²⁶Ra, ²³²Th, and ⁴⁰K activity concentrations, and the composition of U and Th from the Precambrian and Mesozoic rocks in the Jangsu-gun area indicates that monazite is the main accessory mineral controlling the concentration of natural radioactivity. Based on a detailed examination of the natural radioactivity in the rocks of the Jangsu-gun area, the Middle Paleoproterozoic orthogneisses and paragneisses, and Late Triassic and Early Jurassic granitic rocks show average high mean RCI values of 0.88−0.96, such that 32% of the rocks exceeded the recommended value of one in the guidelines for the RCI in South Korea. Especially, the RCI is closely related to the radon levels in the rocks. As a result, the Jangsu-gun area in South Korea is a relatively high radiological risk area, which exhibits higher indoor radon levels in the residences, compared with residences in the other areas in South Korea. Full article

(This article belongs to the Special Issue Geological and Tectonic Evolution of the East Asian Collage: Precambrian and Mesozoic)

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26 pages, 10152 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Paleoenvironment of the Lower–Middle Cambrian Evaporite Series in the Tarim Basin and Its Impact on the Organic Matter Enrichment of Shallow Water Source Rocks

by Mingyang Wei, Zhidong Bao, Axel Munnecke, Wei Liu, G. William M. Harrison, Hua Zhang, Demin Zhang, Zongfeng Li, Xiting Xu, Kai Lu and Zheng Shen

Minerals 2021, 11(7), 659; https://doi.org/10.3390/min11070659 - 22 Jun 2021

Cited by 7 | Viewed by 3311

Abstract

Just as in deep-water sedimentary environments, productive source rocks can be developed in an evaporitic platform, where claystones are interbedded with evaporites and carbonates. However, the impact of the paleoenvironment on the organic matter enrichment of shallow water source rocks in an evaporite [...] Read more.

Just as in deep-water sedimentary environments, productive source rocks can be developed in an evaporitic platform, where claystones are interbedded with evaporites and carbonates. However, the impact of the paleoenvironment on the organic matter enrichment of shallow water source rocks in an evaporite series has not been well explored. In this study, two wells in the central uplift of the Tarim Basin were systematically sampled and analyzed for a basic geochemical study, including major elements, trace elements, and total organic carbon (TOC), to understand the relationship between TOC and the paleoenvironmental parameters, such as paleosalinity, redox, paleoclimate, paleo-seawater depth, and paleoproductivity. The results show that the Lower–Middle Cambrian mainly developed in a fluctuating salinity, weak anoxic to anoxic, continuous dry and hot, and proper shallow water environment. The interfingering section of evaporites, carbonates, and claystones of the Awatag Fm. have higher paleoproductivity and higher enrichment of organic matter. Paleosalinity, redox, paleoclimate, paleo-seawater depth, and paleoproductivity jointly control the organic matter enrichment of shallow water source rocks in the evaporite series. The degree of enrichment of organic matter in shallow water source rocks first increases and then decreases with the increase in paleosalinity. All the samples with high content of organic matter come from the shallower environment of the Awatag Fm. Full article

(This article belongs to the Special Issue Sedimentology, Petrography, Geochemistry and Geobiology of Marine Evaporitic Rocks)

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22 pages, 5712 KiB

Open AccessEditor’s ChoiceArticle

Fluid and Solid Inclusions in Host Minerals of Permian Pegmatites from Koralpe (Austria): Deciphering the Permian Fluid Evolution during Pegmatite Formation

by Kurt Krenn, Martina Husar and Anna Mikulics

Minerals 2021, 11(6), 638; https://doi.org/10.3390/min11060638 - 16 Jun 2021

Cited by 9 | Viewed by 3818

Abstract

Fluid inclusions (FIs) and associated solids in host minerals garnet, tourmaline, spodumene, and quartz from six pegmatite fields of Permian origin at Koralpe (Eastern Alps) have been investigated. Although pegmatites suffered intense Eoalpine high-pressure metamorphic overprint during the Cretaceous period, the studied samples [...] Read more.

Fluid inclusions (FIs) and associated solids in host minerals garnet, tourmaline, spodumene, and quartz from six pegmatite fields of Permian origin at Koralpe (Eastern Alps) have been investigated. Although pegmatites suffered intense Eoalpine high-pressure metamorphic overprint during the Cretaceous period, the studied samples originate from rock sections with well-preserved Permian magmatic textures. Magmatic low-saline aqueous FIs in garnet domains entrapped as part of an unmixed fluid together with primary N₂-bearing FIs that originate from a host rock-derived CO₂-N₂ dominated high-grade metamorphic fluid. This CO₂-N₂ fluid is entrapped as primary FIs in garnet, tourmaline, and quartz. During host mineral crystallization, fluid mixing between the magmatic and the metamorphic fluid at the solvus formed CO₂-N₂-H₂O–rich FIs of various compositional degrees that are preserved as pseudo-secondary inclusions in tourmaline, quartz, and as primary inclusions in spodumene. Intense fluid modification processes by in-situ host mineral–fluid reactions formed a high amount of crystal-rich inclusions in spodumene but also in garnet. The distribution of different types of FIs enables a chronology of pegmatite host mineral growth (garnet-tourmaline/quartz-spodumene) and their fluid chemistry is considered as having exsolved from the pegmatite parent melt together with the metamorphic fluid from the pegmatite host rocks. Minimum conditions for pegmatite crystallization of ca. 4.5–5.5 kbar at 650–750 °C have been constrained by primary FIs in tourmaline that, unlike to FIs in garnet, quartz, and spodumene, have not been affected by post-entrapment modifications. Late high-saline aqueous FIs, only preserved in the recrystallized quartz matrix, are related to a post-pegmatite stage during Cretaceous Eoalpine metamorphism. Full article

(This article belongs to the Special Issue Fluid, Melt and Solid Inclusions as a Petrogenetic Indicators)

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27 pages, 13453 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Exploration of Polymetallic Nodules and Resource Assessment: A Case Study from the German Contract Area in the Clarion-Clipperton Zone of the Tropical Northeast Pacific

by Thomas Kuhn and Carsten Rühlemann

Minerals 2021, 11(6), 618; https://doi.org/10.3390/min11060618 - 9 Jun 2021

Cited by 25 | Viewed by 7086

Abstract

In 2006, the BGR signed a contract with the International Seabed Authority (ISA) for the exploration of polymetallic nodules in the Clarion-Clipperton Zone of the northeast Pacific. During nine expeditions, in particular, “Area E1”, the eastern part of the contract area, with a [...] Read more.

In 2006, the BGR signed a contract with the International Seabed Authority (ISA) for the exploration of polymetallic nodules in the Clarion-Clipperton Zone of the northeast Pacific. During nine expeditions, in particular, “Area E1”, the eastern part of the contract area, with a size of ~60,000 km², was explored in detail. Here, we outline BGR’s exploration methods and provide resource estimates for Area E1 and three sub-areas. The resource assessment is predominantly based on statistical analyses of data obtained by 12-kHz multibeam bathymetry and backscatter mapping, box core sampling and geochemical analysis of nodules. The main parameter for the assessment is the nodule abundance (kg/m²), as its coefficient of variation (CoV) over the entire eastern contract area is relatively high at 36%. In contrast, the metal contents of nodules show only minor variation, with a CoV of 8% for manganese and 8% for the sum of copper, nickel and cobalt. To estimate mineral resources for the entire Area E1, we used an artificial neural network approach with a multivariate statistical correlation between nodule abundance derived from box cores and hydro-acoustic data. The total estimated resources are 540 ± 189 million tonnes (Mt) of dry nodules, and the total estimated metal contents are 168 Mt of manganese, 7.5 Mt of nickel, 6.3 Mt of copper, 0.9 Mt of cobalt, 0.4 Mt of rare-earth elements and 0.3 Mt of molybdenum. A geostatistical resource estimate of three economically prospective areas with a total size of 4498 km², intensively sampled by box cores, was carried out using ordinary kriging of nodule abundance and metal grades. Within these three nodule fields, 7.14 Mt of dry nodules are classified as measured mineral resources covering an area of 489 km². Indicated mineral resources amount to 11.2 Mt, covering an area of 825 km², and inferred mineral resources of 35.5 Mt of dry nodules were estimated for an area of 3184 km². In total, the metal contents of the three prospective areas amount to 16.8 Mt of manganese, 0.74 Mt of nickel, 0.63 Mt of copper and 0.09 Mt of cobalt. Full article

(This article belongs to the Special Issue Exploration of Polymetallic Nodules)

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13 pages, 2286 KiB

Open AccessEditor’s ChoiceArticle

Performance Evaluation of Fe-Al Bimetallic Particles for the Removal of Potentially Toxic Elements from Combined Acid Mine Drainage-Effluents from Refractory Gold Ore Processing

by Elham Aghaei, Zexiang Wang, Bogale Tadesse, Carlito Baltazar Tabelin, Zakaria Quadir and Richard Diaz Alorro

Minerals 2021, 11(6), 590; https://doi.org/10.3390/min11060590 - 31 May 2021

Cited by 20 | Viewed by 4317

Abstract

Acid mine drainage (AMD) is a serious environmental issue associated with mining due to its acidic pH and potentially toxic elements (PTE) content. This study investigated the performance of the Fe-Al bimetallic particles for the treatment of combined AMD-gold processing effluents. Batch experiments [...] Read more.

Acid mine drainage (AMD) is a serious environmental issue associated with mining due to its acidic pH and potentially toxic elements (PTE) content. This study investigated the performance of the Fe-Al bimetallic particles for the treatment of combined AMD-gold processing effluents. Batch experiments were conducted in order to eliminate potentially toxic elements (including Hg, As, Cu, Pb, Ni, Zn, and Mn) from a simulated waste solution at various bimetal dosages (5, 10, and 20 g/L) and time intervals (0 to 90 min). The findings show that metal ions with greater electrode potentials than Fe and Al have higher affinities for electrons released from the bimetal. Therefore, a high removal (>95%) was obtained for Hg, As, Cu, and Pb using 20 g/L bimetal in 90 min. Higher uptakes of Hg, As, Cu, and Pb than Ni, Zn, and Mn also suggest that electrochemical reduction and adsorption by Fe-Al (oxy) hydroxides as the primary and secondary removal mechanisms, respectively. The total Al³⁺ dissolution in the experiments with a higher bimetal content (10 and 20 g/L) were insignificant, while a high release of Fe ions was recorded for various bimetal dosages. Although the secondary Fe pollution can be considered as a drawback of using the Fe-Al bimetal, this issue can be tackled by a simple neutralization and Fe precipitation process. A rapid increase in the solution pH (initial pH 2 to >5 in 90 min) was also observed, which means that bimetallic particles can act as a neutralizing agent in AMD treatment system and promote the precipitation of the dissolved metals. The presence of chloride ions in the system may cause akaganeite formation, which has shown a high removal capacity for PTE. Moreover, nitrate ions may affect the process by competing for the released electrons from the bimetal owing to their higher electrode potential than the metals. Finally, the Fe-Al bimetallic material showed promising results for AMD remediation by electrochemical reduction of PTE content, as well as acid-neutralization/metal precipitation. Full article

(This article belongs to the Special Issue Novel and Emerging Strategies for Sustainable Mine Tailings and Acid Mine Drainage Management)

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19 pages, 3786 KiB

Open AccessEditor’s ChoiceArticle

Origin of the Middle Paleoproterozoic Tiksheozero Ultramafic-Alkaline-Carbonatite Complex, NE Fennoscandian Shield: Evidence from Geochemical and Isotope Sr-Nd-Hf-Pb-Os Data

by Maria Bogina, Boris Belyatsky, Evgenii Sharkov, Alexey Chistyakov and Robert Krymsky

Minerals 2021, 11(6), 570; https://doi.org/10.3390/min11060570 - 27 May 2021

Cited by 3 | Viewed by 3149

Abstract

This article reports new geochemical, Sr-Nd-Hf-Pb and Re-Os data on the rocks of the Middle Paleoproterozoic (1.99 Ga) Tiksheozero ultramafic-alkaline-carbonatite complex confined to the northeastern margin of the Karelian Craton. We focus on the poorly studied silicate rocks. Based on petrographic and geochemical [...] Read more.

This article reports new geochemical, Sr-Nd-Hf-Pb and Re-Os data on the rocks of the Middle Paleoproterozoic (1.99 Ga) Tiksheozero ultramafic-alkaline-carbonatite complex confined to the northeastern margin of the Karelian Craton. We focus on the poorly studied silicate rocks. Based on petrographic and geochemical research, the silicate rocks are subdivided into two groups: an ultramafic-mafic series depleted in REE, and other incompatible elements and an alkaline series enriched in these elements. Isotope studies showed that all rocks have juvenile isotope signatures and were likely derived from a primitive OIB-type mantle source with possible contributions of the subcontinental lithospheric mantle (SCLM). Insignificant crustal contamination is recorded by Pb and Os isotopic compositions. The incompatible element enrichment in the alkaline rocks and depletion in ultramafic-mafic rocks of the mildly alkaline series with allowance for insignificant crustal contamination confirm their derivation from different primary melts. However, a narrow range of Sr, Nd, Hf, and Pb isotope compositions and compact clusters in ²⁰⁷Pb/²⁰⁴Pb-²⁰⁶Pb/²⁰⁴Pb, Nd-⁸⁷Sr/⁸⁶Sr and Hf-Nd isotope diagrams indicate their origination from a common mantle source. A model of subsequent two-stage melting is being most consistent with the geochemical data for this complex. Full article

(This article belongs to the Special Issue Petrogenesis and Geochemistry in Alkaline Ultramafic Rocks)

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26 pages, 8229 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Thermal-Hydrological-Chemical Modeling of a Covered Waste Rock Pile in a Permafrost Region

by Xueying Yi, Danyang Su, Bruno Bussière and K. Ulrich Mayer

Minerals 2021, 11(6), 565; https://doi.org/10.3390/min11060565 - 26 May 2021

Cited by 10 | Viewed by 3819

Abstract

In order to reduce contaminant mass loadings, thermal cover systems may be incorporated in the design of waste rock piles located in regions of continuous permafrost. In this study, reactive transport modeling was used to improve the understanding of coupled thermo-hydrological and chemical [...] Read more.

In order to reduce contaminant mass loadings, thermal cover systems may be incorporated in the design of waste rock piles located in regions of continuous permafrost. In this study, reactive transport modeling was used to improve the understanding of coupled thermo-hydrological and chemical processes controlling the evolution of a covered waste rock pile located in Northern Canada. Material properties from previous field and laboratory tests were incorporated into the model to constrain the simulations. Good agreement between simulated and observational temperature data indicates that the model is capable of capturing the coupled thermo-hydrological processes occurring within the pile. Simulations were also useful for forecasting the pile’s long-term evolution with an emphasis on water flow and heat transport mechanisms, but also including geochemical weathering processes and sulfate mass loadings as an indicator for the release of contaminated drainage. An uncertainty analysis was carried out to address different scenarios of the cover’s performance as a function of the applied infiltration rate, accounting for the impacts of evaporation, runoff, and snow ablation. The model results indicate that the cover performance is insensitive to the magnitude of recharge rates, except for limited changes of the flow regime in the shallow active layer. The model was expanded by performing an additional sensitivity analysis to assess the role of cover thicknesses. The simulated results reveal that a cover design with an appropriate thickness can effectively minimize mass loadings in drainage by maintaining the active layer completely within the cover. Full article

(This article belongs to the Special Issue Environmental Geochemistry in the Mining Environment)

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17 pages, 8663 KiB

Open AccessEditor’s ChoiceArticle

Statherian (ca. 1714–1680 Ma) Extension-Related Magmatism and Deformation in the Southwestern Korean Peninsula and Its Geological Significance: Constraints from the Petrological, Structural, Geochemical and Geochronological Studies of Newly Identified Granitoids

by Byung Choon Lee, Weon-Seo Kee, Uk Hwan Byun and Sung Won Kim

Minerals 2021, 11(6), 557; https://doi.org/10.3390/min11060557 - 24 May 2021

Cited by 4 | Viewed by 2536

Abstract

In this study, petrological, structural, geochemical, and geochronological analyses of the Statherian alkali feldspar granite and porphyritic alkali feldspar granite in the southwestern part of the Korean Peninsula were conducted to examine petrogenesis of the granitoids and their tectonic setting. Zircon U-Pb dating [...] Read more.

In this study, petrological, structural, geochemical, and geochronological analyses of the Statherian alkali feldspar granite and porphyritic alkali feldspar granite in the southwestern part of the Korean Peninsula were conducted to examine petrogenesis of the granitoids and their tectonic setting. Zircon U-Pb dating revealed that the two granites formed around 1.71 Ga and 1.70–1.68 Ga, respectively. The results of the geochemical analyses showed that both of the granites have a high content of K₂O, Nb, Ta, and Y, as well as high FeO^t/MgO and Ga/Al ratios. Both granites have alkali-calcic characteristics with a ferroan composition, indicating an A-type affinity. Zircon Lu-Hf isotopic compositions yielded negative ε_Hf^(t) values (−3.5 to −10.6), indicating a derivation from ancient crustal materials. Both granite types underwent ductile deformation and exhibited a dextral sense of shear with a minor extension component. Based on field relationships and zircon U-Pb dating, it was considered that the deformation event postdated the emplacement of the alkali feldspar granite and terminated soon after the emplacement of the porphyritic alkali feldspar granite in an extensional setting. These data indicated that there were extension-related magmatic activities accompanying ductile deformation in the southwestern part of the Korean Peninsula during 1.71–1.68 Ga. The Statherian extension-related events are well correlated with those in the midwestern part of the Korean and eastern parts of the North China Craton. Full article

(This article belongs to the Special Issue Geological and Tectonic Evolution of the East Asian Collage: Precambrian and Mesozoic)

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13 pages, 3198 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Growth Interruptions in Arctic Rhodoliths Correspond to Water Depth and Rhodolith Morphology

by Moritz Schlüter, Ines Pyko, Max Wisshak, Christian Schulbert and Sebastian Teichert

Minerals 2021, 11(5), 538; https://doi.org/10.3390/min11050538 - 19 May 2021

Cited by 8 | Viewed by 3549

Abstract

Coralline algae that form rhodoliths are widespread globally and their skeletal growth patterns have been used as (paleo-) environmental proxies in a variety of studies. However, growth interruptions (hiati) within their calcareous skeletons are regarded as problematic in this context. Here we investigated [...] Read more.

Coralline algae that form rhodoliths are widespread globally and their skeletal growth patterns have been used as (paleo-) environmental proxies in a variety of studies. However, growth interruptions (hiati) within their calcareous skeletons are regarded as problematic in this context. Here we investigated how hiati in the growth of Arctic rhodoliths from the Svalbard archipelago correspond to their environment and morphology. Using X-ray micro-computed tomography and stepwise model selections, we found that rhodoliths from deeper waters are subject to more frequent hiatus formation. In addition, rhodoliths with a higher sphericity (i.e., roundness) are less often affected by such growth interruptions. We conclude that these correlations are mainly regulated by hydrodynamics, because, in deeper waters, rhodoliths are not turned frequently enough to prevent a dieback of coralline algal thalli forming on the underside of the rhodolith. In this coherence, spheroidal rhodoliths are turned more easily, therefore shortening the amount of time between turnover events. Moreover, the incidence of light is more advantageous in shallower waters where rhodoliths exhibit a greater share of their surface to diffused ambient light, thus enabling thallus growth also on the down-facing surface of the rhodoliths. In consequence, information on the frequency of hiatus formation combined with rhodolith morphology might serve as a valuable proxy for (paleo-)environmental reconstructions in respect to light availability and the hydrodynamic regime. Full article

(This article belongs to the Special Issue Polar Marine Carbonates)

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13 pages, 15691 KiB

Open AccessEditor’s ChoiceArticle

Investigation on Dynamical Mechanics, Energy Dissipation, and Microstructural Characteristics of Cemented Tailings Backfill under SHPB Tests

by Di Zheng, Weidong Song, Shuai Cao, Jiajian Li and Lijuan Sun

Minerals 2021, 11(5), 542; https://doi.org/10.3390/min11050542 - 19 May 2021

Cited by 24 | Viewed by 2956

Abstract

As mining depth increases, the backfill mining method is more and more widely used in underground mines. The dynamic load generated by the blasting can affect the stability of the cemented tailings backfill (CTB). The CTB samples were prepared to conduct a test [...] Read more.

As mining depth increases, the backfill mining method is more and more widely used in underground mines. The dynamic load generated by the blasting can affect the stability of the cemented tailings backfill (CTB). The CTB samples were prepared to conduct a test of the split Hopkinson pressure bar (SHPB) to investigate the dynamic disturbance of CTB. The present paper discusses dynamical mechanics, energy dissipation, and microstructure analysis of CTB. Micro-computer tomography (micro-CT) scanning of CTB samples after the SHPB test was performed to analyze the evolution of internal cracks. The experimental results showed that when the average strain rate (ASR) increased from 30 to 98 s⁻¹, the dynamic uniaxial compression strength (DUCS) of the CTB showed a trend of first increasing and decreasing with the increase in ASR. The dynamic stress–strain pre-peak curve of CTB directly enters the linear elastic stage. As ASR increases, the absorbed energy of the CTB shows a trend of first increasing and then decreasing. Moreover, according to the micro-CT scanning results, the crack area of CTB accounts for about 16% of the sample near the incident bar and about 1% near the transmitted bar. The crack area ratio is exponentially related to the specimen height. These findings can provide reasonable dynamical CTB strength data selection for underground pillar mining. Full article

(This article belongs to the Special Issue Backfilling Materials for Underground Mining, Volume II)

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69 pages, 23883 KiB

Open AccessEditor’s ChoiceReview

Noble Metal Speciations in Hydrothermal Sulphides

by Ilya Vikentyev, Olga Vikent’eva, Eugenia Tyukova, Maximilian Nikolsky, Julia Ivanova, Nina Sidorova, Dmitry Tonkacheev, Vera Abramova, Vyacheslav Blokov, Adelina Spirina, Diana Borisova and Galina Palyanova

Minerals 2021, 11(5), 488; https://doi.org/10.3390/min11050488 - 3 May 2021

Cited by 21 | Viewed by 5172

Abstract

A significant part of the primary gold reserves in the world is contained in sulphide ores, many types of which are refractory in gold processing. The deposits of refractory sulphide ores will be the main potential source of gold production in the future. [...] Read more.

A significant part of the primary gold reserves in the world is contained in sulphide ores, many types of which are refractory in gold processing. The deposits of refractory sulphide ores will be the main potential source of gold production in the future. The refractory gold and silver in sulphide ores can be associated with micro- and nano-sized inclusions of Au and Ag minerals as well as isomorphous, adsorbed and other species of noble metals (NM) not thoroughly investigated. For gold and gold-bearing deposits of the Urals, distribution and forms of NM were studied in base metal sulphides by laser ablation-inductively coupled plasma mass spectrometry and by neutron activation analysis. Composition of arsenopyrite and As-pyrite, proper Au and Ag minerals were identified using electron probe microanalysis. The ratio of various forms of invisible gold—which includes nanoparticles and chemically bound gold—in sulphides is discussed. Observations were also performed on about 120 synthetic crystals of NM-doped sphalerite and greenockite. In VMS ores with increasing metamorphism, C_Au and C_Ag in the major sulphides (sphalerite, chalcopyrite, pyrite) generally decrease. A portion of invisible gold also decreases —from ~65–85% to ~35–60% of the total Au. As a result of recrystallisation of ores, the invisible gold is enlarged and passes into the visible state as native gold, Au-Ag tellurides and sulphides. In the gold deposits of the Urals, the portion of invisible gold is usually <30% of the bulk Au. Full article

(This article belongs to the Special Issue Mineralogy of Noble Metals and “Invisible” Speciations of These Elements in Natural Systems, Volume II)

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18 pages, 14944 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Petrographic Investigation of the Carboniferous Sequence from the Ibbenbüren Mine: Tracing the Origin of the Coal Mine Drainage

by Diego Bedoya-Gonzalez, Sylke Hilberg, Günther Redhammer and Thomas Rinder

Minerals 2021, 11(5), 483; https://doi.org/10.3390/min11050483 - 30 Apr 2021

Cited by 3 | Viewed by 3071

Abstract

The mine drainage of the Ibbenbüren anthracite coal mine is characterized by exceptionally high concentrations of dissolved iron and sulfate. The elevated position of the coal field with respect to the surrounding area makes the neighboring sediments an unlikely source of these elements. [...] Read more.

The mine drainage of the Ibbenbüren anthracite coal mine is characterized by exceptionally high concentrations of dissolved iron and sulfate. The elevated position of the coal field with respect to the surrounding area makes the neighboring sediments an unlikely source of these elements. Accordingly, it has been hypothesized that interaction between infiltrating rainwater and the fractured overburden is a key process governing the mine drainage chemistry. To test this hypothesis, two full-diameter core samples drilled above the discharging adit of the coal mine were investigated. The methodology combined several analytical techniques to identify and characterize traces of water–rock interaction related to both diagenesis and relatively recent weathering processes along open fractures. The coupled appearance of kaolinite-dickite-illite minerals in weathered and unweathered rock sections was clearly connected to the burial history of the Carboniferous sequence. In contrast, the formation of iron (oxide-) hydroxides together with the presence of oxidized pyrite in weathering profiles along both sides of the fractures was positively related to the geochemical footprint of the coal mine drainage. Thus, open fractures, possibly originated from mining activities, may play a significant role in the drainage chemistry, especially considering the rather poor hydraulic conditions of the overburden. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Coal-Bearing Rocks)

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36 pages, 23918 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Origin of the Moroccan Touissit-Bou Beker and Jbel Bou Dahar Supergene Non-Sulfide Biomineralization and Its Relevance to Microbiological Activity, Late Miocene Uplift and Climate Changes

by Mohammed Bouabdellah, Wissale Boukirou, Adriana Potra, Erik Melchiorre, Hassan Bouzahzah, Johan Yans, Khadra Zaid, Mohammed Idbaroud, Julien Poot, Augustin Dekoninck and Gilles Levresse

Minerals 2021, 11(4), 401; https://doi.org/10.3390/min11040401 - 11 Apr 2021

Cited by 14 | Viewed by 5923

Abstract

Through integration of Pb-Zn ± Cu non-sulfide mineralogy, texture, and stable isotope (C, O, S) geochemistry, the world-class Touissit- Bou Beker and Jbel Bou Dahar Mississippi Valley-type districts of the Moroccan Atlasic system have been investigated in order to gain insights into the [...] Read more.

Through integration of Pb-Zn ± Cu non-sulfide mineralogy, texture, and stable isotope (C, O, S) geochemistry, the world-class Touissit- Bou Beker and Jbel Bou Dahar Mississippi Valley-type districts of the Moroccan Atlasic system have been investigated in order to gain insights into the origin and processes that contributed to the formation of the base metal non-sulfide mineralization. In both districts, direct replacement (“red calamine”) and wallrock replacement (“white calamine”) ores are observed. Based on the mineral assemblages, ore textures, and crosscutting relations, three distinct mineralizing stages are recognized. The earliest, pre-non-sulfide gossanous stage was a prerequisite for the following supergene stages and constituted the driving force that ultimately promoted the leaching of most base metals such as Zn and Cu and alkalis from their rock sources. The following two stages, referred to as the main supergene “red calamine” and late “white calamine” ore stages, generated the bulk of mineable “calamine” ores in the Touissit-Bou Beker and Jbel Bou Dahar districts. Stable isotope compositions (δ¹³C_V-PDB, δ¹⁸O_V-SMOW, δ³⁴S_CDT) support a three-stage model whereby metals were released by supergene acidic fluids and then precipitated by bacteria and archaea-mediated metal-rich meteoric fluids due to a decrease in temperature and/or increase of f_O2. Oxygen isotope thermometry indicates decreasing precipitation temperatures with advancing paragenetic sequence from 33° to 18 °C, with wet to semi-arid to arid climatic conditions. The close spatial relationships between coexisting sulfide and non-sulfide mineralization along with stable isotope constraints suggest that the oxidation of sulfides occurred concurrently after the main stage of the Alpine orogeny between 15 Ma and the present. More importantly, the current data show for the first time the involvement of biologically controlled activity as the major driving process that triggered both oxidation and deposition of supergene mineralization at Jbel Bou Dahar and Touissit-Bou Beker districts. Conclusions drawn from this study therefore have implications for supergene Mississippi Valley-type (MVT) -derived non-sulfide deposits worldwide and account for the prominent role of biological processes in the genesis of this category of ore deposits. Full article

(This article belongs to the Special Issue Supergene Evolution of Polymetallic Deposits, including Non-laterite Fe and Mn Ores)

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20 pages, 8068 KiB

Open AccessEditor’s ChoiceArticle

Industrial Vertical Stirred Mills Screw Liner Wear Profile Compared to Discrete Element Method Simulations

by Priscila M. Esteves, Douglas B. Mazzinghy, Roberto Galéry and Luís C. R. Machado

Minerals 2021, 11(4), 397; https://doi.org/10.3390/min11040397 - 10 Apr 2021

Cited by 20 | Viewed by 7564

Abstract

Vertical stirred mills have been widely applied in the minerals industry, due to its greater efficiency in comparison with conventional tumbling mills. In this context, the agitator liner wear plays an important role in maintenance planning and operational costs. In this paper, we [...] Read more.

Vertical stirred mills have been widely applied in the minerals industry, due to its greater efficiency in comparison with conventional tumbling mills. In this context, the agitator liner wear plays an important role in maintenance planning and operational costs. In this paper, we use the discrete element method (DEM) wear simulation to evaluate the screw liner wear. Three different mill rotational velocities are evaluated in the simulation, according to different scale-up procedures. The wear profile, wear measurement, power consumption, and particle contact information are used for obtaining a better understanding of the wear behavior and its effects on grinding mechanisms. Data from a vertical stirred mill screw liner wear measurement obtained in a full-scale mill are used to correlate with simulation results. The results indicate a relative agreement with industrial measurement in most of the liner lifecycle, when using a proper mill velocity scale-up. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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31 pages, 8403 KiB

Open AccessEditor’s ChoiceArticle

Automated Gold Grain Counting. Part 2: What a Gold Grain Size and Shape Can Tell!

by Réjean Girard, Jonathan Tremblay, Alexandre Néron, Hugues Longuépée and Sheida Makvandi

Minerals 2021, 11(4), 379; https://doi.org/10.3390/min11040379 - 2 Apr 2021

Cited by 7 | Viewed by 3698

Abstract

Glacial drift exploration methods are well established and widely used by mineral industry exploring for blind deposit in northern territories, and rely on the dispersion of mineral or chemical signal in sediments derived from an eroded mineralized source. Gold grains themselves are the [...] Read more.

Glacial drift exploration methods are well established and widely used by mineral industry exploring for blind deposit in northern territories, and rely on the dispersion of mineral or chemical signal in sediments derived from an eroded mineralized source. Gold grains themselves are the prime indicator minerals to be used for the detection of blind gold deposits. Surprisingly, very little attention has been dedicated to the information that size and shape of gold grain can provide, other than a simple shape classification based on modification affecting the grains that are induced in the course of sediment transport. With the advent of automated scanning electron microscope (SEM)-based gold grain detection, high magnification backscattered electron images of each grain are routinely acquired, which can be used for accurate size measurement and shape analysis. A library with 88,613 gold grain images has been accumulated from various glacial sediment surveys on the Canadian Shield and used to detect trends in grains size and shape. A series of conclusions are drawn: (1) grain size distribution is consistent among various surveys and areas, (2) there is no measurable fine-grained gold loss due to natural elutriation in ablation or reworked till, or during the course of reverse circulation drilling, (3) there is no grain size sorting during glacial transport, severing small grains from large ones, (4) shape modification induced by transport is highly dependent on grain size and original shapes, and (5) the use of grain shape inherited from neighboring minerals in the source rocks is a useful feature when assessing deposit types and developing exploration strategies. Full article

(This article belongs to the Special Issue The Application of Automated SEM-Based Identification of Detrital, Diagenetic and Indicator Mineral Phases)

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24 pages, 7668 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Complexity of Respirable Dust Found in Mining Operations as Characterized by X-ray Diffraction and FTIR Analysis

by Rachel L. T. Walker, Emanuele Cauda, Lauren Chubb, Patrick Krebs, Robert Stach, Boris Mizaikoff and Cliff Johnston

Minerals 2021, 11(4), 383; https://doi.org/10.3390/min11040383 - 2 Apr 2021

Cited by 11 | Viewed by 3427

Abstract

The mineralogical complexity of mine dust complicates exposure monitoring methods for occupational, respirable hazards. Improved understanding of the variability in respirable dust characteristics, e.g., mineral phase occurrence and composition, is required to advance on-site monitoring techniques that can be applied across diverse mining [...] Read more.

The mineralogical complexity of mine dust complicates exposure monitoring methods for occupational, respirable hazards. Improved understanding of the variability in respirable dust characteristics, e.g., mineral phase occurrence and composition, is required to advance on-site monitoring techniques that can be applied across diverse mining sectors. Principal components analysis (PCA) models were applied separately to XRD and FTIR datasets collected on 130 respirable dust samples from seven mining commodities to explore similarities and differences among the samples. Findings from both PCA models classified limestone, iron, and granite mine samples via their analytical responses. However, the results also cautioned that respirable samples from these commodities may not always fit patterns observed within the model. For example, one unique sample collected in a limestone mine contained no carbonate minerals. Future predictive quantification models should account for unique samples. Differences between gold and copper mine dust samples were difficult to observe. Further investigation suggested that the key to their differentiation by FTIR may lie in the characterization of clays. The results presented in this study provide foundational information for guiding the development of quantification models for respirable mineral hazards in the mining industry. Full article

(This article belongs to the Special Issue Mineralogy and Characteristics of Occupational and Environmental Dust Exposures)

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18 pages, 5369 KiB

Open AccessEditor’s ChoiceArticle

Numerical Modelling of Radiogenic Ingrowth and Diffusion of Pb in Apatite Inclusions with Variable Shape and U-Th Zonation

by Daniil V. Popov and Richard A. Spikings

Minerals 2021, 11(4), 364; https://doi.org/10.3390/min11040364 - 31 Mar 2021

Cited by 3 | Viewed by 3208

Abstract

The fundamental premise of apatite U-Th-Pb thermochronology is that radiogenic Pb is redistributed by volume diffusion. In practice, it is often additionally assumed that crystals (1) lose radiogenic Pb to an infinite reservoir, (2) have a simple geometry and (3) are chemically homogeneous. [...] Read more.

The fundamental premise of apatite U-Th-Pb thermochronology is that radiogenic Pb is redistributed by volume diffusion. In practice, it is often additionally assumed that crystals (1) lose radiogenic Pb to an infinite reservoir, (2) have a simple geometry and (3) are chemically homogeneous. Here we explore the significance of the latter three assumptions by numerical modelling of Pb radiogenic ingrowth and diffusion in apatite inclusions within other minerals. Our results indicate that the host minerals are likely to hamper diffusive Pb loss from the apatite inclusions by limiting the Pb flux across their boundaries, and thus the thermal histories that are reconstructed assuming a fully open boundary may be significantly inaccurate, precluding a meaningful interpretation. We also find that when apatite boundaries are flux-limited, heterogeneities in U and Th concertation within apatite have subordinate effect on bulk-grain U-Th-Pb dates and can cause intra-grain U-Th-Pb dates to increase towards the boundaries. Finally, we show that it is important to correctly account for crystal geometry when modelling intra-grain U-Th-Pb dates. We suggest that the effect of surrounding minerals on diffusive Pb loss from apatite (and loss of other radiogenic isotopes from other minerals) should be examined more closely in future research. Full article

(This article belongs to the Special Issue Thermochronology at Temperatures Higher than 150 °C)

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20 pages, 6171 KiB

Open AccessEditor’s ChoiceArticle

Recovering Magnetization of Rock Formations by Jointly Inverting Airborne Gravity Gradiometry and Total Magnetic Intensity Data

by Michael Jorgensen and Michael S. Zhdanov

Minerals 2021, 11(4), 366; https://doi.org/10.3390/min11040366 - 31 Mar 2021

Cited by 21 | Viewed by 3592

Abstract

Conventional 3D magnetic inversion methods are based on the assumption that there is no remanent magnetization, and the inversion is run for magnetic susceptibility only. This approach is well-suited to targeting mineralization; however, it ignores the situation where the direction of magnetization of [...] Read more.

Conventional 3D magnetic inversion methods are based on the assumption that there is no remanent magnetization, and the inversion is run for magnetic susceptibility only. This approach is well-suited to targeting mineralization; however, it ignores the situation where the direction of magnetization of the rock formations is different from the direction of the induced magnetic field. We present a novel method of recovering a spatial distribution of magnetization vector within the rock formation based on joint inversion of airborne gravity gradiometry (AGG) and total magnetic intensity (TMI) data for a shared earth model. Increasing the number of inversion parameters (the scalar components of magnetization vector) results in a higher degree of non-uniqueness of the inverse problem. This increase of non-uniqueness rate can be remedied by joint inversion based on (1) Gramian constraints or (2) joint focusing stabilizers. The Gramian constraints enforce shared earth structure through a correlation of the model gradients. The joint focusing stabilizers also enforce the structural similarity and are implemented using minimum support or minimum gradient support approaches. Both novel approaches are applied to the interpretation of the airborne data collected over the Thunderbird V-Ti-Fe deposit in Ontario, Canada. By combining the complementary AGG and TMI data, we generate jointly inverted shared earth models that provide a congruent image of the rock formations hosting the mineral deposit. Full article

(This article belongs to the Special Issue Geophysics for Mineral Exploration)

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15 pages, 2706 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Prediction of Postflotation Tailings Behavior in a Large Storage Facility

by Magdalena Wróżyńska

Minerals 2021, 11(4), 362; https://doi.org/10.3390/min11040362 - 30 Mar 2021

Cited by 2 | Viewed by 2451

Abstract

Extracting and copper production on a large scale generates large volumes of postflotation mine tailings. The scale of operation and development of tailings storage facilities (TSFs) forces the use of innovative solutions enabling safe storage now and in the future. Any changes to [...] Read more.

Extracting and copper production on a large scale generates large volumes of postflotation mine tailings. The scale of operation and development of tailings storage facilities (TSFs) forces the use of innovative solutions enabling safe storage now and in the future. Any changes to the operation require multi-directional monitoring of the impact of these changes on storage safety. The ongoing exploitation will be ensured by expansion of the TSF and a change in tailings storage technology. This approach will preclude the need for changes to the new location, such as changes of land use, and will minimise the volume of mine waste. The paper presents the results of pilot studies carried out to implement the change in postflotation tailings storage technology at Żelazny Most TSF (Poland) in the future. The aim of the paper was settlements prediction of tailings and comparison of deformations with observed settlements. Settlements prediction of tailings was made on the basis of the results of the DMT (Marchetti Dilatometer Test), recommended for the prediction of natural soil settlement. Depending on the analysed zone of the TSF, settlements ranged from a few centimetres to over 1.5 m. Despite the difference shown, the results of DMT and geodetic measurements indicate a convergent trend of settlement. Full article

(This article belongs to the Special Issue Innovative Strategies for Solid Waste Minimisation in the Mining and Minerals Industry)

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23 pages, 10032 KiB

Open AccessEditor’s ChoiceArticle

Evolution of Pyrite Compositions at the Sizhuang Gold Deposit, Jiaodong Peninsula, Eastern China: Implications for the Genesis of Jiaodong-Type Orogenic Gold Mineralization

by Zhankun Liu, Xiancheng Mao, Andrew Jedemann, Richard C. Bayless, Hao Deng, Jin Chen and Keyan Xiao

Minerals 2021, 11(4), 344; https://doi.org/10.3390/min11040344 - 26 Mar 2021

Cited by 27 | Viewed by 4766

Abstract

Gold deposits in the Jiaodong Peninsula represent a primary gold resource in China and mostly exhibit similar ore-forming features related to sericite-quartz-pyrite alteration and other controls from (micro-)structural deformation. This study investigates the pyrite textures and trace elements in the Sizhuang gold deposit [...] Read more.

Gold deposits in the Jiaodong Peninsula represent a primary gold resource in China and mostly exhibit similar ore-forming features related to sericite-quartz-pyrite alteration and other controls from (micro-)structural deformation. This study investigates the pyrite textures and trace elements in the Sizhuang gold deposit (>100 t Au) to document the key factors impacting on the genesis of the Jiaodong-type orogenic deposits. Three main types of pyrite are identified: (1) the first generation of pyrite (Py1) occurs as disseminated euhedral to subhedral grains in K-feldspar-albite-rutile-hematite and sericite alteration (stage 1), (2) Py2 as aggregates in quartz-sericite-pyrite altered rocks or quartz-pyrite veins (stage 2) can be subdivided into Py2a as irregular cores, Py2b as a zoned overgrowth on Py2a, and Py2c as overgrowth on early pyrite, and (3) Py3 as fine-grained crystals in siderite-polymetallic veins (stage 3). Primary gold at the Sizhuang deposit is coevally or slightly later deposited with Py2b, Py2c, and Py3. Laser ablation–inductively coupled plasma mass spectrometry (LA–ICP–MS) analyses show that the highest Co and Ni contents in Py1 and high but variable Co in Py2b favors the involvement of deep high-temperature magmatic waters at stage 1 and middle stage 2. The elevated As contents from Py2a to Py2c and depletion of trace elements (e.g., Co, Ni, As and Te) and high Au/Co, Cu/Ni, and As/Ni values in Py2a and Py3, combined with published H-O isotope data, imply a meteoric water ingress during stage 2–3. Thus, the fluid evolution at Sizhuang is a consequence of pulsed deep magmatic fluid release plus progressive meteoric fluid ingress. The rhythmic Co–As–Ni–Au bands of Py2b additionally suggest episodic changes in the composition of ore-forming fluids. Moreover, the sharp textural features (e.g., pyrite overgrowth on previously cataclastic crystals) of Py2 and As-Cu-rich and Co-poor bands in zoned Py2b probably also reflect rapid metal deposition and self-organization and subsequent mineral crystal growth due to the pressure release during phase separation in the Sizhuang deposit. Considering the significantly concentrated gold (>1300 t) in the regional Jiaojia fault zone and Au-bearing mineral formation related to phase separation (boiling) in the Sizhuang deposit, gold mineralization in the Sizhuang deposit was interpreted to be controlled by the pressure-driver owing to the seismic activities in the Jiaojia fault system. Full article

(This article belongs to the Special Issue Advances in Quantitative LA-ICP-MS Analysis Promoting New Understanding of Gold Ore Genesis)

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22 pages, 3151 KiB

Open AccessEditor’s ChoiceArticle

Thermodynamic Constraints on Smectite and Iron Oxide Formation at Gale Crater, Mars: Insights into Potential Free Energy from Aerobic Fe Oxidation in Lake Water–Groundwater Mixing Zone

by Sakiko Kikuchi and Takazo Shibuya

Minerals 2021, 11(4), 341; https://doi.org/10.3390/min11040341 - 25 Mar 2021

Cited by 9 | Viewed by 3598

Abstract

The presence of saponite and iron oxides in Sheepbed mudstone of Yellowknife Bay at Gale crater on Mars is considered as evidence of a habitable fluvio-lacustrine environment for chemolithoautotrophy. However, the energetic availability for metabolic reactions is poorly constrained. Herein, we propose the [...] Read more.

The presence of saponite and iron oxides in Sheepbed mudstone of Yellowknife Bay at Gale crater on Mars is considered as evidence of a habitable fluvio-lacustrine environment for chemolithoautotrophy. However, the energetic availability for metabolic reactions is poorly constrained. Herein, we propose the possible mixing of surface water and groundwater that (i) explains the formation of magnetite and hematite detected in Sheepbed mudstone and (ii) may work as a potential habitable zone for aerobic Fe²⁺-oxidizing microbes. Our thermodynamic modeling of water–rock reactions revealed that the formation of abundant saponite in Sheepbed mudstone may occur under various conditions of water-to-rock mass ratios, temperatures (5–200 °C), and initial fluid compositions. In contrast, the formation of iron oxides in the mudstone can be explained only by the mixing of Fe²⁺-rich groundwater and more oxidized surface waters, where the Fe²⁺-rich groundwater can be generated by the low-temperature water–rock reactions with a CO₂-bearing initial fluid. The calculated bioavailable energy of aerobic Fe²⁺ oxidation in the fluid-mixing zone on Mars is similar to that estimated for a fluid-mixing zone on Earth actually inhabited by aerobic Fe²⁺-oxidizing microbes. The findings will contribute to a better understanding of potential habitability on Mars. Full article

(This article belongs to the Special Issue Expanding Views of Clays, Oxides, and Evaporites on Aquaplanets in the Solar System)

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18 pages, 4979 KiB

Open AccessEditor’s ChoiceArticle

The Binding of Phosphorus Species at Goethite: A Joint Experimental and Theoretical Study

by Prasanth B. Ganta, Mohsen Morshedizad, Oliver Kühn, Peter Leinweber and Ashour A. Ahmed

Minerals 2021, 11(3), 323; https://doi.org/10.3390/min11030323 - 20 Mar 2021

Cited by 15 | Viewed by 5326

Abstract

Knowledge of the interaction between inorganic and organic phosphates with soil minerals is vital for improving soil P-fertility. To achieve an in-depth understanding, we combined adsorption experiments and hybrid ab initio molecular dynamics simulations to analyze the adsorption of common phosphates, i.e., orthophosphate [...] Read more.

Knowledge of the interaction between inorganic and organic phosphates with soil minerals is vital for improving soil P-fertility. To achieve an in-depth understanding, we combined adsorption experiments and hybrid ab initio molecular dynamics simulations to analyze the adsorption of common phosphates, i.e., orthophosphate (OP), glycerolphosphate (GP) and inositolhexaphosphate (IHP), onto the 100 surface plane of goethite. Experimental adsorption data per mol P-molecule basis fitted to the Freundlich model show the adsorption strength increases in the order GP < OP < IHP, and IHP adsorption being saturated faster followed by GP and OP. Modeling results show that OP and GP form stable monodentate (M) and binuclear bidentate (B) motifs, with B being more stable than M, whereas IHP forms stable M and 3M motifs. Interfacial water plays an important role through hydrogen bonds and proton transfers with OP/GP/IHP and goethite. It also controls the binding motifs of phosphates with goethite. Combining both experimental and modeling results, we propose that the B motif dominates for OP, whereas GP forms M and IHP forms a combination of M and 3M motifs. The joint approach plausibly explains why IHP is the predominant organically bound P form in soil. This study could be considered as a preliminary step for further studies for understanding the mechanisms of how microbes and plants overcome strong IHP–mineral binding to implement the phosphate groups into their metabolism. Full article

(This article belongs to the Special Issue Recent Advances in Molecular Modeling of Clay Minerals Interfaces)

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14 pages, 2991 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Theoretical Study on Thermal Release of Helium-3 in Lunar Ilmenite

by Hongqing Song, Jie Zhang, Yueqiang Sun, Yongping Li, Xianguo Zhang, Dongyu Ma and Jue Kou

Minerals 2021, 11(3), 319; https://doi.org/10.3390/min11030319 - 19 Mar 2021

Cited by 9 | Viewed by 5131

Abstract

The in-situ utilization of lunar helium-3 resource is crucial to manned lunar landings and lunar base construction. Ilmenite was selected as the representative mineral which preserves most of the helium-3 in lunar soil. The implantation of helium-3 ions into ilmenite was simulated to [...] Read more.

The in-situ utilization of lunar helium-3 resource is crucial to manned lunar landings and lunar base construction. Ilmenite was selected as the representative mineral which preserves most of the helium-3 in lunar soil. The implantation of helium-3 ions into ilmenite was simulated to figure out the concentration profile of helium-3 trapped in lunar ilmenite. Based on the obtained concentration profile, the thermal release model for molecular dynamics was established to investigate the diffusion and release of helium-3 in ilmenite. The optimal heating temperature, the diffusion coefficient, and the release rate of helium-3 were analyzed. The heating time of helium-3 in lunar ilmenite under actual lunar conditions was also studied using similitude analysis. The results show that after the implantation of helium-3 into lunar ilmenite, it is mainly trapped in vacancies and interstitials of ilmenite crystal and the corresponding concentration profile follows a Gaussian distribution. As the heating temperature rises, the cumulative amounts of released helium-3 increase rapidly at first and then tend to stabilize. The optimal heating temperature of helium-3 is about 1000 K and the corresponding cumulative release amount is about 74%. The diffusion coefficient and activation energy of helium-3 increase with the temperature. When the energy of helium-3 is higher than the binding energy of the ilmenite lattice, the helium-3 is released rapidly on the microscale. Furthermore, when the heating temperature increases, the heating time for thermal release of helium-3 under actual lunar conditions decreases. For the optimal heating temperature of 1000 K, the thermal release time of helium-3 is about 1 s. The research could provide a theoretical basis for in-situ helium-3 resources utilization on the moon. Full article

(This article belongs to the Section Mineral Geochemistry and Geochronology)

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22 pages, 3809 KiB

Open AccessEditor’s ChoiceArticle

Strength Characteristics of Clay–Rubber Waste Mixtures in Low-Frequency Cyclic Triaxial Tests

by Małgorzata Jastrzębska and Krzysztof Tokarz

Minerals 2021, 11(3), 315; https://doi.org/10.3390/min11030315 - 18 Mar 2021

Cited by 17 | Viewed by 3864

Abstract

This paper presents the results of consolidated and undrained (CU) triaxial cyclic tests related to the influence of tire waste addition on the strength characteristics of two different soils from Southern Poland: unswelling kaolin and swelling red clay. The test procedure included the [...] Read more.

This paper presents the results of consolidated and undrained (CU) triaxial cyclic tests related to the influence of tire waste addition on the strength characteristics of two different soils from Southern Poland: unswelling kaolin and swelling red clay. The test procedure included the normally consolidated remolded specimens prepared from pure red clay (RC) and kaolin (K) and their mixtures with two different fractions of shredded rubber powder (P) and granulate (G) in 5%, 10%, and 25% mass proportions. All samples were subjected to low-frequency cyclic loading carried out with a constant stress amplitude. Analysis of the results includes consideration of the effect of rubber additive and number of load cycles on the development of excess pore pressure and axial strain during the cyclic load operation and on the maximum stress deviator value. A general decrease in the shear strength due to the cyclic load operation was observed, and various effects of shear strength depended on the mixture content and size of the rubber waste particles. In general, the use of soil–rubber mixtures, especially for expansive soils and powder, should be treated with caution for cyclic loading. Full article

(This article belongs to the Special Issue Stabilisation and Reinforcement of Clays with Environmentally Friendly Materials)

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21 pages, 5642 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Impact of Grinding of Printed Circuit Boards on the Efficiency of Metal Recovery by Means of Electrostatic Separation

by Tomasz Suponik, Dawid M. Franke, Paweł M. Nuckowski, Piotr Matusiak, Daniel Kowol and Barbara Tora

Minerals 2021, 11(3), 281; https://doi.org/10.3390/min11030281 - 9 Mar 2021

Cited by 18 | Viewed by 4925

Abstract

This paper analyses the impact of the method of grinding printed circuit boards (PCBs) in a knife mill on the efficiency and purity of products obtained during electrostatic separation. The separated metals and plastics and ceramics can be used as secondary raw materials. [...] Read more.

This paper analyses the impact of the method of grinding printed circuit boards (PCBs) in a knife mill on the efficiency and purity of products obtained during electrostatic separation. The separated metals and plastics and ceramics can be used as secondary raw materials. This is in line with the principle of circular economy. Three different screen perforations were used in the mill to obtain different sizes of ground grains. Moreover, the effect of cooling the feed to cryogenic temperature on the final products of separation was investigated. The level of contamination of the concentrate, intermediate, and waste obtained as a result of the application of fixed, determined electrostatic separation parameters was assessed using ICP-AES, SEM–EDS, XRD, and microscopic analysis as well as specific density. The yields of grain classes obtained from grinding in a knife mill were tested through sieve analysis and by using a particle size analyser. The test results indicate that using a knife mill with a 1 mm screen perforation along with cooling the feed to cryogenic temperature significantly improves the efficiency of the process. The grinding products were characterised by the highest release level of the useful substance—metals in the free state. The purity of the concentrate and waste obtained from electrostatic separation was satisfactory, and the content of the intermediate, in which conglomerates of solid metal–plastic connections were present, was very low. The yield of concentrate and waste amounted to 26.2% and 71.0%, respectively. Their purity, reflected in the content of the identified metals (valuable metals), was at the level of 93.3% and 0.5%, respectively. In order to achieve effective recovery of metals from PCBs by means of electrostatic separation, one should strive to obtain a feed composed of grains <1000 μm and, optimally, <800 μm. Full article

(This article belongs to the Special Issue Recovery of Precious Metals, Rare Earth Elements and Special Metals from Spent Secondary Products)

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23 pages, 6913 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Active Treatment of Contaminants of Emerging Concern in Cold Mine Water Using Advanced Oxidation and Membrane-Related Processes: A Review

by Sébastien Ryskie, Carmen M. Neculita, Eric Rosa, Lucie Coudert and Patrice Couture

Minerals 2021, 11(3), 259; https://doi.org/10.3390/min11030259 - 2 Mar 2021

Cited by 18 | Viewed by 5555

Abstract

Responsible use and effective treatment of mine water are prerequisites of sustainable mining. The behavior of contaminants in mine water evolves in relation to the metastable characteristics of some species, changes related to the mine life cycle, and mixing processes at various scales. [...] Read more.

Responsible use and effective treatment of mine water are prerequisites of sustainable mining. The behavior of contaminants in mine water evolves in relation to the metastable characteristics of some species, changes related to the mine life cycle, and mixing processes at various scales. In cold climates, water treatment requires adaptation to site-specific conditions, including high flow rates, salinity, low temperatures, remoteness, and sensitivity of receiving waterbodies. Contaminants of emerging concern (CECs) represent a newer issue in mine water treatment. This paper reviews recent research on the challenges and opportunities related to CECs in mine water treatment, with a focus on advanced oxidation and membrane-based processes on mine sites operating in cold climates. Finally, the paper identifies research needs in mine water treatment. Full article

(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)

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27 pages, 8457 KiB

Open AccessEditor’s ChoiceArticle

Contamination Alters the Physicochemical and Textural Characteristics of Clays in the Sediments of the Peri Urban Reconquista River, Affecting the Associated Indigenous Microorganisms

by Ana E. Tufo, Susana Vázquez, Natalia F. Porzionato, María Celeste Grimolizzi, María Belén Prados, Mauricio Sica and Gustavo Curutchet

Minerals 2021, 11(3), 242; https://doi.org/10.3390/min11030242 - 26 Feb 2021

Cited by 7 | Viewed by 3920

Abstract

The physicochemical and textural characteristics of river sediments and, essentially, their clays, are at the center of a network of biological and geochemical factors that are mutually modifying. Therefore, the contamination, the characteristics of the clays, and the associated microorganisms strongly influence each [...] Read more.

The physicochemical and textural characteristics of river sediments and, essentially, their clays, are at the center of a network of biological and geochemical factors that are mutually modifying. Therefore, the contamination, the characteristics of the clays, and the associated microorganisms strongly influence each other. In this work, sediments from two sites of the urban Reconquista River, near Buenos Aires City, Argentina, exposed to different environmental contexts were characterized. The huge differences in the organic matter content in the vertical profile between both sediments strongly evidenced the polluted status of San Francisco (SF) site as opposed to the Dique Roggero (DR) site. Thorough physicochemical and textural characterization of the sediments and their clay fraction performed by pH, Oxidation-reduction potential (ORP), spectrophotometry, XRD, laser diffraction, N₂ adsorption–desorption isotherms, EDS, and SEM measurements revealed that organic matter (DR: 41 ± 5 g kg⁻¹; SF: 150 ± 30 g kg⁻¹) intervened in the retention of heavy metals (DR: 5.6 mg kg⁻¹ Zn, 7 mg kg⁻¹ Cu, 3.1 kg⁻¹ Cr; SF: 240 mg kg⁻¹ Zn, 60 mg kg⁻¹ Cu, 270 mg kg⁻¹ Cr) and affected the level of association and the formation of mineral–organic aggregates (DR: 15 ± 3 μm; SF: 23 ± 4 μm). This can be decisive in the surface interaction required for the establishment of bacterial assemblages, which determine the biogeochemical processes occurring in sediments and have a key role in the fate of contaminants in situ and in the remediation processes that need to be applied to restore the anoxic contaminated sediments. Full article

(This article belongs to the Special Issue Clay Minerals–Life Interplay)

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14 pages, 1180 KiB

Open AccessEditor’s ChoiceArticle

Soil Biochemical Indicators and Biological Fertility in Agricultural Soils: A Case Study from Northern Italy

by Livia Vittori Antisari, Chiara Ferronato, Mauro De Feudis, Claudio Natali, Gianluca Bianchini and Gloria Falsone

Minerals 2021, 11(2), 219; https://doi.org/10.3390/min11020219 - 20 Feb 2021

Cited by 17 | Viewed by 4353

Abstract

Industrial farming without considering soil biological features could lead to soil degradation. We aimed to evaluate the biochemical properties (BPs) and biological fertility (BF) of different soils under processing tomato cultivation; estimate the BF through the calculation of a simplified BF index (BFIs); [...] Read more.

Industrial farming without considering soil biological features could lead to soil degradation. We aimed to evaluate the biochemical properties (BPs) and biological fertility (BF) of different soils under processing tomato cultivation; estimate the BF through the calculation of a simplified BF index (BFIs); determine if the crop was affected by BP and BF. Three farms were individuated in Modena (MO), Ferrara (MEZ) and Ravenna (RA) provinces, Italy. Soil analysis included total and labile organic C, microbial biomass-C (Cmic) and microbial respiration measurements. The metabolic (qCO₂), mineralization (qM) and microbial (qMIC) quotients, and BFIs were calculated. Furthermore, plant nutrient contents were determined. The low Cmic content and qMIC, and high qCO₂ found in MEZ soils indicate the occurrence of stressful conditions. The high qMIC and qM, and the low qCO₂ demonstrated an efficient organic carbon incorporation as Cmic in MO soils. In RA soils, the low total and labile organic C contents limited the Cmic and microbial respiration. Therefore, as confirmed by the BFIs, while MO showed the healthiest soils, RA soils had an inefficient ecophysiological energy state. However, no effects on plant nutrient contents were observed, likely because of masked by fertigation. Finally, BP monitoring is needed in order to avoid soil degradation and, in turn, crop production decline. Full article

(This article belongs to the Special Issue Elemental and Isotope Geochemistry of the Earth’s Critical Zone)

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27 pages, 6824 KiB

Open AccessEditor’s ChoiceReview

REEs in the North Africa P-Bearing Deposits, Paleoenvironments, and Economic Perspectives: A Review

by Roberto Buccione, Rabah Kechiched, Giovanni Mongelli and Rosa Sinisi

Minerals 2021, 11(2), 214; https://doi.org/10.3390/min11020214 - 19 Feb 2021

Cited by 34 | Viewed by 6558

Abstract

A review of the compositional features of Tunisia, Algeria, and Morocco phosphorites is proposed in order to assess and compare the paleoenvironmental conditions that promoted the deposit formation as well as provide information about their economic perspective in light of growing worldwide demand. [...] Read more.

A review of the compositional features of Tunisia, Algeria, and Morocco phosphorites is proposed in order to assess and compare the paleoenvironmental conditions that promoted the deposit formation as well as provide information about their economic perspective in light of growing worldwide demand. Since these deposits share a very similar chemical and mineralogical composition, the attention was focused on the geochemistry of rare earth elements (REEs) and mostly on ΣREEs, Ce and Eu anomalies, and (La/Yb) and (La/Gd) normalized ratios. The REEs distributions reveal several differences between deposits from different locations, suggesting mostly that the Tunisian and Algerian phosphorites probably were part of the same depositional system. There, sub-reducing to sub-oxic conditions and a major REEs adsorption by early diagenesis were recorded. Conversely, in the Moroccan basins, sub-oxic to oxic environments and a minor diagenetic alteration occurred, which was likely due to a different seawater supply. Moreover, the drastic environmental changes associated to the Paleocene–Eocene Thermal Maximum event probably influenced the composition of Northern African phosphorites that accumulated the highest REEs amounts during that span of time. Based on the REEs concentrations, and considering the outlook coefficient of REE composition (K_outl) and the percentage of critical elements in ΣREEs (REE_def), the studied deposits can be considered as promising to highly promising REE ores and could represent a profitable alternative source for critical REEs. Full article

(This article belongs to the Special Issue Feature Papers in Mineral Deposits 2020)

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17 pages, 7834 KiB

Open AccessEditor’s ChoiceArticle

Mechanism and Influencing Factors of REY Enrichment in Deep-Sea Sediments

by Jiangbo Ren, Yan Liu, Fenlian Wang, Gaowen He, Xiguang Deng, Zhenquan Wei and Huiqiang Yao

Minerals 2021, 11(2), 196; https://doi.org/10.3390/min11020196 - 13 Feb 2021

Cited by 39 | Viewed by 4297

Abstract

Deep-sea sediments with high contents of rare-earth elements and yttrium (REY) are expected to serve as a potential resource for REY, which have recently been proved to be mainly contributed by phosphate component. Studies have shown that the carriers of REY in deep-sea [...] Read more.

Deep-sea sediments with high contents of rare-earth elements and yttrium (REY) are expected to serve as a potential resource for REY, which have recently been proved to be mainly contributed by phosphate component. Studies have shown that the carriers of REY in deep-sea sediments include aluminosilicate, Fe-Mn oxyhydroxides, and phosphate components. The ∑REY of the phosphate component is 1–2 orders of magnitude higher than those of the other two carriers, expressed as ∑REY = 0.001 × [Al₂O₃] − 0.002 × [MnO] + 0.056 × [P₂O₅] − 32. The sediment P₂O₅ content of 1.5% explains 89.1% of the total variance of the sediment ∑REY content. According to global data, P has a stronger positive correlation with ∑REY compared with Mn, Fe, Al, etc.; 45.5% of samples have a P₂O₅ content of less than 0.25%, and ∑REY of not higher than 400 ppm. The ∑REY of the phosphate component reaches n × 10⁴ ppm, much higher than that of marine phosphorites and lower than that of REY-phosphate minerals, which are called REY-rich phosphates in this study. The results of microscopic observation and separation by grain size indicate that the REY-rich phosphate component is mainly composed of bioapatite. When ∑REY > 2000 ppm, the average CaO/P₂O₅ ratio of the samples is 1.55, indicating that the phosphate composition is between carbonate fluoroapatite and hydroxyfluorapatite. According to a knowledge map of sediment elements, the phosphate component is mainly composed of P, Ca, Sr, REY, Sc, U, and Th, and its chemical composition is relatively stable. The phosphate component has a negative Ce anomaly and positive Y anomaly, and a REY pattern similar to that of marine phosphorites and seawater. After the early diagenesis process (biogeochemistry, adsorption, desorption, transformation, and migration), the REY enrichment in the phosphate component is completed near the seawater/sediment interface. In the process of REY enrichment, the precipitation and enrichment of P is critical. According to current research progress, the REY enrichment is the result of comprehensive factors, including low sedimentation rate, high ∑REY of the bottom seawater, a non-carbonate depositional environment, oxidation conditions, and certain bottom current conditions. Full article

(This article belongs to the Special Issue Economic Potential and Characteristics of REE Deposits and Other Critical Raw Materials)

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18 pages, 7747 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Geoecological Zonation of Revegetation Enhances Biodiversity at Historic Mine Sites, Southern New Zealand

by Dave Craw and Cathy Rufaut

Minerals 2021, 11(2), 181; https://doi.org/10.3390/min11020181 - 9 Feb 2021

Cited by 10 | Viewed by 3362

Abstract

Rocks exposed by mining can form physically, mineralogically, and geochemically diverse surface substrates. Engineered mine rehabilitation typically involves covering these rocks with a uniform layer of soil and vegetation. An alternative approach is to encourage the establishment of plant species that are tolerant [...] Read more.

Rocks exposed by mining can form physically, mineralogically, and geochemically diverse surface substrates. Engineered mine rehabilitation typically involves covering these rocks with a uniform layer of soil and vegetation. An alternative approach is to encourage the establishment of plant species that are tolerant of challenging geochemical settings. The zonation of geochemical parameters can therefore lead to geoecological zonation and enhanced biodiversity. Abandoned gold mines in southern New Zealand have developed such geoecological zonations that resulted from establishment of salt-tolerant ecosystems on substrates with evaporative NaCl. A salinity threshold equivalent to substrate electrical conductivity of 1000 µS separates this ecosystem from less salt-tolerant plant ecosystems. Acid mine drainage from pyrite-bearing waste rocks at an abandoned coal mine has caused variations in surface pH between 1 and 7. The resultant substrate pH gradients have led to differential plant colonisation and the establishment of distinctive ecological zones. Substrate pH <3 remained bare ground, whereas pH 3–4 substrates host two acid-tolerant shrubs. These shrubs are joined by a tree species between pH 4 and 5. At higher pH, all local species can become established. The geoecological zonation, and the intervening geochemical thresholds, in these examples involve New Zealand native plant species. However, the principle of enhancing biodiversity by the selection or encouragement of plant species tolerant of diverse geochemical conditions on exposed mine rocks is applicable for site rehabilitation anywhere in the world. Full article

(This article belongs to the Special Issue Environmental Geochemistry in the Mining Environment)

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25 pages, 16141 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

UAS-Based Hyperspectral Environmental Monitoring of Acid Mine Drainage Affected Waters

by Hernan Flores, Sandra Lorenz, Robert Jackisch, Laura Tusa, I. Cecilia Contreras, Robert Zimmermann and Richard Gloaguen

Minerals 2021, 11(2), 182; https://doi.org/10.3390/min11020182 - 9 Feb 2021

Cited by 47 | Viewed by 9860

Abstract

The exposure of metal sulfides to air or water, either produced naturally or due to mining activities, can result in environmentally damaging acid mine drainage (AMD). This needs to be accurately monitored and remediated. In this study, we apply high-resolution unmanned aerial system [...] Read more.

The exposure of metal sulfides to air or water, either produced naturally or due to mining activities, can result in environmentally damaging acid mine drainage (AMD). This needs to be accurately monitored and remediated. In this study, we apply high-resolution unmanned aerial system (UAS)-based hyperspectral mapping tools to provide a useful, fast, and non-invasive method for the monitoring aspect. Specifically, we propose a machine learning framework to integrate visible to near-infrared (VNIR) hyperspectral data with physicochemical field data from water and sediments, together with laboratory analyses to precisely map the extent of acid mine drainage in the Tintillo River (Spain). This river collects the drainage from the western part of the Rio Tinto massive sulfide deposit and discharges large quantities of acidic water with significant amounts of dissolved metals (Fe, Al, Cu, Zn, amongst others) into the Odiel River. At the confluence of these rivers, different geochemical and mineralogical processes occur due to the interaction of very acidic water (pH 2.5–3.0) with neutral water (pH 7.0–8.0). This complexity makes the area an ideal test site for the application of hyperspectral mapping to characterize both rivers and better evaluate contaminated water bodies with remote sensing imagery. Our approach makes use of a supervised random forest (RF) regression for the extended mapping of water properties, using the samples collected in the field as ground-truth and training data. The resulting maps successfully estimate the concentration of dissolved metals and related physicochemical properties in water, and trace associated iron species (e.g., jarosite, goethite) within sediments. These results highlight the capabilities of UAS-based hyperspectral data to monitor water bodies in mining environments, by mapping their hydrogeochemical properties, using few field samples. Hence, we have demonstrated that our workflow allows the rapid discrimination and mapping of AMD contamination in water, providing an essential basis for monitoring and subsequent remediation. Full article

(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)

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10 pages, 11526 KiB

Open AccessEditor’s ChoiceArticle

Twinning of Tetrahedrite—OD Approach

by Emil Makovicky

Minerals 2021, 11(2), 170; https://doi.org/10.3390/min11020170 - 7 Feb 2021

Cited by 2 | Viewed by 2714

Abstract

The common twinning of tetrahedrite and tennantite can be described as an order–disorder (OD) phenomenon. The unit OD layer is a one-tetrahedron-thick (111) layer composed of six-member rings of tetrahedra, with gaps between them filled with Sb(As) coordination pyramids and triangular-coordinated (Cu, Ag). [...] Read more.

The common twinning of tetrahedrite and tennantite can be described as an order–disorder (OD) phenomenon. The unit OD layer is a one-tetrahedron-thick (111) layer composed of six-member rings of tetrahedra, with gaps between them filled with Sb(As) coordination pyramids and triangular-coordinated (Cu, Ag). The stacking sequence of six-member rings is ABCABC, which can also be expressed as a sequence of three consecutive tetrahedron configurations, named α, β, and γ. When the orientation of component tetrahedra is uniform, the α, β, γ, α sequence builds the familiar cage structure of tetrahedrite. However, when the tetrahedra of the β layer are rotated by 180° against those in the underlying α configurations and/or when a rotated α configuration follows after the β configuration (instead of γ), twinning is generated. If repeated, this could generate the ABAB sequence which would modify the structure considerably. If the rest of the structure grows as a regular cubic tetrahedrite structure, the single occurrence of the described defect sequences creates a twin. Full article

(This article belongs to the Special Issue Modularity and Twinning in Mineral Crystal Structures)

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15 pages, 820 KiB

Open AccessEditor’s ChoiceReview

Ocean-Floor Sediments as a Resource of Rare Earth Elements: An Overview of Recently Studied Sites

by Jelena Milinovic, Francisco J. L. Rodrigues, Fernando J. A. S. Barriga and Bramley J. Murton

Minerals 2021, 11(2), 142; https://doi.org/10.3390/min11020142 - 30 Jan 2021

Cited by 33 | Viewed by 6748

Abstract

The rare earth elements (REE), comprising 15 elements of the lanthanum series (La-Lu) together with yttrium (Y) and scandium (Sc), have become of particular interest because of their use, for example, in modern communications, renewable energy generation, and the electrification of transport. However, [...] Read more.

The rare earth elements (REE), comprising 15 elements of the lanthanum series (La-Lu) together with yttrium (Y) and scandium (Sc), have become of particular interest because of their use, for example, in modern communications, renewable energy generation, and the electrification of transport. However, the security of supply of REE is considered to be at risk due to the limited number of sources, with dependence largely on one supplier that produced approximately 63% of all REE in 2019. As a result, there is a growing need to diversify supply. This has resulted in the drive to seek new resources elsewhere, and particularly on the deep-ocean floor. Here, we give a summary of REE distribution in minerals, versatile applications, and an update of their economic value. We present the most typical onshore methods for the determination of REE and examine methods for their offshore exploration in near real time. The motivation for this comes from recent studies over the past decade that showed ΣREE concentrations as high as 22,000 ppm in ocean-floor sediments in the Pacific Ocean. The ocean-floor sediments are evaluated in terms of their potential as resources of REE, while the likely economic cost and environmental impacts of deep-sea mining these are also considered. Full article

(This article belongs to the Special Issue Genesis and Exploration for Submarine Sulphide Deposits)

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39 pages, 19761 KiB

Open AccessEditor’s ChoiceArticle

Mineralogy and Geochemistry of Deep-Sea Sediments from the Ultraslow-Spreading Southwest Indian Ridge: Implications for Hydrothermal Input and Igneous Host Rock

by Xian Chen, Xiaoming Sun, Zhongwei Wu, Yan Wang, Xiao Lin and Hongjun Chen

Minerals 2021, 11(2), 138; https://doi.org/10.3390/min11020138 - 29 Jan 2021

Cited by 13 | Viewed by 5184

Abstract

Detailed mineralogical and geochemical characteristics of typical surface sediments and hydrothermal deposits collected from the ultraslow-spreading Southwest Indian Ridge (SWIR) were studied by high-resolution XRD, SEM-EDS, XRF, and ICP-MS. The SWIR marine samples can be generally classified into two main categories: surface sediment [...] Read more.

Detailed mineralogical and geochemical characteristics of typical surface sediments and hydrothermal deposits collected from the ultraslow-spreading Southwest Indian Ridge (SWIR) were studied by high-resolution XRD, SEM-EDS, XRF, and ICP-MS. The SWIR marine samples can be generally classified into two main categories: surface sediment (biogenic, volcanic) and hydrothermal-derived deposit; moreover, the surface sediment can be further classified into metalliferous and non-metalliferous based on the metalliferous sediment index (MSI). The chemical composition of biogenic sediment (mainly biogenic calcite) was characterized by elevated contents of Ca, Ba, Rb, Sr, Th, and light rare earth elements (LREE), while volcanic sediment (mainly volcanogenic debris) was relatively enriched in Mn, Mg, Al, Si, Ni, Cr, and high field strength elements (HFSEs). By contrast, the hydrothermal-derived deposit (mainly pyrite-marcasite, chalcopyrite-isocubanite, and low-temperature cherts) contained significantly higher contents of Fe, Cu, Zn, Pb, Mn, Co, Mo, Ag, and U. In addition, the metalliferous surface sediment contained a higher content of Cu, Mn, Fe, Co, Mo, Ba, and As. Compared with their different host (source) rock, the basalt-hosted marine sediments contained higher contents of Ti–Al–Zr–Sc–Hf and/or Mo–Ba–Ag; In contrast, the peridotite-hosted marine sediments were typically characterized by elevated concentrations of Mg–Cu–Ni–Cr and/or Co–Sn–Au. The differences in element enrichment and mineral composition between these sediment types were closely related to their sedimentary environments (e.g., near/far away from the vent sites) and inherited from their host (source) rock. Together with combinations of certain characteristic elements (such as Al–Fe–Mn and Si–Al–Mg), relict hydrothermal products, and diagnostic mineral tracers (e.g., nontronite, SiO_2(bio), olivine, serpentine, talc, sepiolite, pyroxene, zeolite, etc.), it would be more effective to differentiate the host rock of deep-sea sediments and to detect a possible hydrothermal input. Full article

(This article belongs to the Special Issue Genesis and Exploration for Submarine Sulphide Deposits)

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16 pages, 1859 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Low-Temperature Chlorite Geothermometry and Related Recent Analytical Advances: A Review

by Franck Bourdelle

Minerals 2021, 11(2), 130; https://doi.org/10.3390/min11020130 - 28 Jan 2021

Cited by 38 | Viewed by 6628

Abstract

Chlorite, a 2:1:1 phyllosilicate, has all the required attributes to form the basis of a geothermometer: this mineral is ubiquitous in metamorphic, diagenetic, and hydrothermal systems with a broad field of stability and a chemical composition partly dependent on temperature (T) and pressure [...] Read more.

Chlorite, a 2:1:1 phyllosilicate, has all the required attributes to form the basis of a geothermometer: this mineral is ubiquitous in metamorphic, diagenetic, and hydrothermal systems with a broad field of stability and a chemical composition partly dependent on temperature (T) and pressure (P) conditions. These properties led to the development of a multitude of chlorite thermometers, ranging from those based on empirical calibrations (linking T to Al^IV content) to thermodynamic or semi-empirical models (linking T to chlorite + quartz + water equilibrium constant). This present study provides an overview of these geothermometers proposed in the literature for low-temperature chlorite (T < 350 °C), specifying the advantages and limitations of each method. Recent analytical developments that allow for circumventing or responding to certain criticisms regarding the low-temperature application of thermometers are also presented. The emphasis is on micrometric and nanometric analysis, highlighting chemical intracrystalline zoning—which can be considered as evidence of a succession of local equilibria justifying a thermometric approach—and mapping ferric iron content. New perspectives in terms of analysis (e.g., Mn redox in Mn-chlorite) and geothermometer (molecular solid-solution model, oxychlorite end-member) are also addressed. Full article

(This article belongs to the Special Issue Advances in Low-Temperature Mineralogy and Geochemistry)

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28 pages, 11013 KiB

Open AccessEditor’s ChoiceArticle

Rare-Metal (In, Bi, Te, Se, Be) Mineralization of Skarn Ores in the Pitkäranta Mining District, Ladoga Karelia, Russia

by Vasily I. Ivashchenko

Minerals 2021, 11(2), 124; https://doi.org/10.3390/min11020124 - 27 Jan 2021

Cited by 16 | Viewed by 4732

Abstract

The results of the study of rare-metal (Bi, Te, Se. Be, In) mineralization of skarn deposits (Sn, Zn) in the Pitkäranta Mining District, genetically related to the Salmi anorthosite-rapakivi granite batholiths of Early Riphean age are reported. Minerals and their chemical composition were [...] Read more.

The results of the study of rare-metal (Bi, Te, Se. Be, In) mineralization of skarn deposits (Sn, Zn) in the Pitkäranta Mining District, genetically related to the Salmi anorthosite-rapakivi granite batholiths of Early Riphean age are reported. Minerals and their chemical composition were identified on the base of optical microscopy as well as electron microanalysis. The diversity of rare-metal ore mineralization (native metals, oxides, and hydroxides, carbonates, tellurides, selenides, sulfides, sulphosalts, borates, and silicates) in Pitkäranta Mining District ores is indicative of considerable variations in the physicochemical conditions of their formation controlled by the discrete-pulse-like supply of fluids. Bismuth, wittichenite, and matildite are the most common rare-metal minerals. Sulfosalts of the bismuthinite-aikinite series are represented only by its end-members. The absence of solid solution exsolution structures in sulfobismuthides suggests that they crystallized from hydrothermal solutions at low temperatures. Be (>10 minerals) and In (roquesite) minerals occur mainly in aposkarn greisens. Roquesite in Pitkäranta Mining District ores formed upon greisen alteration of skarns with In released upon the alteration of In-bearing solid sphalerite (Cu¹⁺ In³⁺) ↔ (Zn²⁺, Fe²⁺) and chalcopyrite In³⁺ ↔ Fe³⁺ and 2Fe³⁺ ↔ (Fe²⁺, Zn²⁺) Sn⁴⁺ solutions. Sphalerite with an average In concentration of 2001 ppm, is a major In-bearing mineral in the ores. Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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14 pages, 3499 KiB

Open AccessEditor’s ChoiceReview

Specific Refractory Gold Flotation and Bio-Oxidation Products: Research Overview

by Richmond K. Asamoah

Minerals 2021, 11(1), 93; https://doi.org/10.3390/min11010093 - 19 Jan 2021

Cited by 31 | Viewed by 7090

Abstract

This paper presents a research overview, reconciling key and useful case study findings, towards uncovering major causes of gold refractoriness and maximising extraction performance of specific gold flotation and bio-oxidation products. Through systematic investigation of the ore mineralogical and gold deportment properties, leaching [...] Read more.

This paper presents a research overview, reconciling key and useful case study findings, towards uncovering major causes of gold refractoriness and maximising extraction performance of specific gold flotation and bio-oxidation products. Through systematic investigation of the ore mineralogical and gold deportment properties, leaching mechanisms, and kinetic behaviour and pulp rheology, it was observed that the predominant cause of the poor extraction efficacy of one bio-oxidised product is the presence of recalcitrant sulphate minerals (e.g., jarosite and gypsum) produced during the oxidation process. This was followed by carbonaceous matter and other gangue minerals such as muscovite, quartz, and rutile. The underpining leaching mechanism and kinetics coupled with the pulp rheology were influenced by the feed mineralogy/chemistry, time, agitation/shear rate, interfacial chemistry, pH modifier type, and mechano-chemical activation. For instance, surface exposure of otherwise unavailable gold particles by mechano-chemical activation enhanced the gold leaching rate and yield. This work reflect the remarkable impact of subtle deposit feature changes on extraction performance. Full article

(This article belongs to the Special Issue Moving towards the Crystal Structure, Molecular or Atomic-Scale for Green and Novel Hydrometallurgical Processing)

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16 pages, 4477 KiB

Open AccessEditor’s ChoiceArticle

Fly Ash Utilisation in Mullite Fabrication: Development of Novel Percolated Mullite

by Pramod Koshy, Naomi Ho, Vicki Zhong, Luisa Schreck, Sandor Alex Koszo, Erik J. Severin and Charles Christopher Sorrell

Minerals 2021, 11(1), 84; https://doi.org/10.3390/min11010084 - 16 Jan 2021

Cited by 8 | Viewed by 3947

Abstract

Fly ash is an aluminosilicate and the major by-product from coal combustion in power stations; its increasing volumes are major economic and environmental concerns, particularly since it is one of the largest mineral resources based on current estimates. Mullite (3Al₂O₃ [...] Read more.

Fly ash is an aluminosilicate and the major by-product from coal combustion in power stations; its increasing volumes are major economic and environmental concerns, particularly since it is one of the largest mineral resources based on current estimates. Mullite (3Al₂O₃·2SiO₂) is the only stable phase in the Al₂O₃-SiO₂ system and is used in numerous applications owing to its high-temperature chemical and mechanical stabilities. Hence, fly ash offers a potential economical resource for mullite fabrication, which is confirmed by a review of the current literature. This review details the methodologies to utilise fly ash with different additives to fabricate what are described as porous interconnected mullite skeletons or dense mullite bodies of approximately stoichiometric compositions. However, studies of pure fly ash examined only high-Al₂O₃ forms and none of these works reported long-term, high-temperature, firing shrinkage data for these mullite bodies. In the present work, high-SiO₂ fly ashes were used to fabricate percolated mullite, which is demonstrated by the absence of firing shrinkage upon long-term high-temperature soaking. The major glass component of the fly ash provides viscosities suitably high for shape retention but low enough for ionic diffusion and the minor mullite component provides the nucleating agent to grow mullite needles into a direct-bonded, single-crystal, continuous, needle network that prevents high-temperature deformation and isolates the residual glass in the triple points. These attributes confer outstanding long-term dimensional stability at temperatures exceeding 1500 °C, which is unprecedented for mullite-based compositions. Full article

(This article belongs to the Special Issue Utilisation of Industrial Byproducts for Materials and Metallurgical Applications)

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24 pages, 15020 KiB

Open AccessEditor’s ChoiceArticle

Viscosity and Strength Properties of Cemented Tailings Backfill with Fly Ash and Its Strength Predicted

by Jie Wang, Jianxin Fu, Weidong Song and Yongfang Zhang

Minerals 2021, 11(1), 78; https://doi.org/10.3390/min11010078 - 15 Jan 2021

Cited by 19 | Viewed by 3118

Abstract

It is of great significance to study the effect of solid contents (SC), binder-to-tailings (b/t) ratio, types and dosage of fly ash (FA) on the viscosity (V) and uniaxial compressive strength (UCS) of backfill. It can improve filling efficiency and reduce [...] Read more.

It is of great significance to study the effect of solid contents (SC), binder-to-tailings (b/t) ratio, types and dosage of fly ash (FA) on the viscosity (V) and uniaxial compressive strength (UCS) of backfill. It can improve filling efficiency and reduce filling costs to understand the relationship between SC, b/t ratio, FA dosage and viscosity, and UCS of backfill. Consequently, this paper carried out uniaxial compression tests and rheological tests on five different types of backfill specimens. Experimental results indicate that, with the increase of SC, the viscosity and UCS of all backfill samples increases as a power function. With the decrease of b/t ratio, the viscosity and UCS of all backfill samples decreases as an exponential function. The coupling effect of SC and b/t ratio has a great influence on the viscosity and UCS of backfill samples. The relationship between SC, b/t ratio and viscosity, and UCS is a quadratic polynomial function. The order of the viscosity of the backfill slurry is: pure tailings < backfill slurry mixed with Ordinary Portland Cement (OPC) < backfill slurry mixed with FA1 < backfill slurry mixed with FA2. The higher the FA dosage, the greater the viscosity. The order of the UCS of backfill is: backfill with OPC > backfill with FA1 > backfill with FA2. The higher the FA dosage, the smaller the UCS. The UCS of all backfill samples increased with the increase of curing time (CT). The relations between the viscosity and UCS of backfill present the positively linear functions. It is feasible to use viscosity to predict the UCS of backfill, and the error between the UCS predicted value and the test value is mostly controlled within 10%. Ultimately, the findings of the experimental work will provide a scientific reference for the mine to design the strength of the backfill. Full article

(This article belongs to the Section Mineral Processing and Extractive Metallurgy)

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12 pages, 3526 KiB

Open AccessEditor’s ChoiceArticle

Adsorption of Pharmaceuticals onto Smectite Clay Minerals: A Combined Experimental and Theoretical Study

by Gwenaëlle Corbin, Emmanuelle Vulliet, Bruno Lanson, Albert Rimola and Pierre Mignon

Minerals 2021, 11(1), 62; https://doi.org/10.3390/min11010062 - 11 Jan 2021

Cited by 19 | Viewed by 3799

Abstract

The adsorption of two pharmaceuticals, carbamazepine and paracetamol, onto the expandable clay mineral saponite has been studied through the combination of kinetic experiments, X-ray diffraction, and theoretical modeling. Kinetic experiments indicate low adsorption for carbamazepine and paracetamol on expandable smectite clay. Accordingly, X-ray [...] Read more.

The adsorption of two pharmaceuticals, carbamazepine and paracetamol, onto the expandable clay mineral saponite has been studied through the combination of kinetic experiments, X-ray diffraction, and theoretical modeling. Kinetic experiments indicate low adsorption for carbamazepine and paracetamol on expandable smectite clay. Accordingly, X-ray diffraction experiments show that neither compound enters smectite interlayer space. Molecular dynamics simulations were carried out to understand the interactions between the two pharmaceuticals and the saponite basal surface in the presence of Na⁺ cations. Calculations reveal that paracetamol almost does not coordinate solution cations, whereas a rather low coordination to cation is observed for carbamazepine. As a result, the adsorption onto the clay surface results mainly from van der Waals interactions for both pharmaceuticals. Carbamazepine does adsorb the surface via two configurations, one involving cation coordination, which corresponds to a rather stable adsorption compared to paracetamol. This is confirmed by structural analyses completed with desorption free energy profile. Full article

(This article belongs to the Special Issue Recent Advances in Molecular Modeling of Clay Minerals Interfaces)

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19 pages, 9747 KiB

Open AccessEditor’s ChoiceArticle

A Novel Particle-Based Approach for Modeling a Wet Vertical Stirred Media Mill

by Simon Larsson, Juan Manuel Rodríguez Prieto, Hannu Heiskari and Pär Jonsén

Minerals 2021, 11(1), 55; https://doi.org/10.3390/min11010055 - 9 Jan 2021

Cited by 18 | Viewed by 3712

Abstract

Modeling of wet stirred media mill processes is challenging since it requires the simultaneous modeling of the complex multiphysics in the interactions between grinding media, the moving internal agitator elements, and the grinding fluid. In the present study, a multiphysics model of an [...] Read more.

Modeling of wet stirred media mill processes is challenging since it requires the simultaneous modeling of the complex multiphysics in the interactions between grinding media, the moving internal agitator elements, and the grinding fluid. In the present study, a multiphysics model of an HIG5 pilot vertical stirred media mill with a nominal power of 7.5 kW is developed. The model is based on a particle-based coupled solver approach, where the grinding fluid is modeled with the particle finite element method (PFEM), the grinding media are modeled with the discrete element method (DEM), and the mill structure is modeled with the finite element method (FEM). The interactions between the different constituents are treated by loose (or weak) two-way couplings between the PFEM, DEM, and FEM models. Both water and a mineral slurry are used as grinding fluids, and they are modeled as Newtonian and non-Newtonian fluids, respectively. In the present work, a novel approach for transferring forces between grinding fluid and grinding media based on the Reynolds number is implemented. This force transfer is realized by specifying the drag coefficient as a function of the Reynolds number. The stirred media mill model is used to predict the mill power consumption, dynamics of both grinding fluid and grinding media, interparticle contacts of the grinding media, and the wear development on the mill structure. The numerical results obtained within the present study show good agreement with experimental measurements. Full article

(This article belongs to the Special Issue Simulation Using the Discrete Element Method (DEM) in the Minerals Industry)

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16 pages, 4239 KiB

Open AccessEditor’s ChoiceArticle

Mineralogical and Geochemical Characterization of Gold Mining Tailings and Their Potential to Generate Acid Mine Drainage (Minas Gerais, Brazil)

by Mariana Lemos, Teresa Valente, Paula Marinho Reis, Rita Fonseca, Itamar Delbem, Juliana Ventura and Marcus Magalhães

Minerals 2021, 11(1), 39; https://doi.org/10.3390/min11010039 - 31 Dec 2020

Cited by 32 | Viewed by 5965

Abstract

For more than 30 years, sulfide gold ores were treated in metallurgic plants located in Nova Lima, Minas Gerais, Brazil, and accumulated in the Cocoruto tailings dam. Both flotation and leaching tailings from a deactivated circuit, as well as roasted and leaching tailings [...] Read more.

For more than 30 years, sulfide gold ores were treated in metallurgic plants located in Nova Lima, Minas Gerais, Brazil, and accumulated in the Cocoruto tailings dam. Both flotation and leaching tailings from a deactivated circuit, as well as roasted and leaching tailings from an ongoing plant, were studied for their acid mine drainage potential and elements’ mobility. Detailed characterization of both tailings types indicates the presence of fine-grain size material hosting substantial amounts of sulfides that exhibit distinct geochemical and mineralogical characteristics. The samples from the ongoing plant show high grades of Fe in the form of oxides, cyanide, and sulfates. Differently, samples from the old circuit shave higher average concentrations of Al (0.88%), Ca (2.4%), Mg (0.96%), and Mn (0.17%), present as silicates and carbonates. These samples also show relics of preserved sulfides, such as pyrite and pyrrhotite. Concentrations of Zn, Cu, Au, and As are higher in the tailings of the ongoing circuit, while Cr and Hg stand out in the tailings of the deactivated circuit. Although the obtained results show that the sulfide wastes do not tend to generate acid mine drainage, leaching tests indicate the possibility of mobilization of toxic elements, namely As and Mn in the old circuit, and Sb, As, Fe, Ni, and Se in the tailings of the plant that still works. This work highlights the need for proper management and control of tailing dams even in alkaline drainage environments such as the one of the Cocoruto dam. Furthermore, strong knowledge of the tailings’ dynamics in terms of geochemistry and mineralogy would be pivotal to support long-term decisions on wastes management and disposal. Full article

(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)

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