Minerals

11 pages, 3048 KiB

Open AccessArticle

The Characterization and Amoxicillin Adsorption Activity of Mesopore CaCO₃ Microparticles Prepared Using Rape Flower Pollen

by Lvshan Zhou, Tongjiang Peng, Hongjuan Sun, Xiaogang Guo and Dong Fu

Minerals 2019, 9(4), 254; https://doi.org/10.3390/min9040254 - 25 Apr 2019

Cited by 10 | Viewed by 3438

Abstract

A precipitation reaction method was employed to prepare mesopore calcium carbonate (CaCO₃) using rape flower pollen as the template. CaCO₃ adsorbent was characterized using X-ray diffraction (XRD), scanning electronic microscopy (SEM), and Brunner−Emmet−Teller measurements (BET). The equilibrium adsorption data on [...] Read more.

A precipitation reaction method was employed to prepare mesopore calcium carbonate (CaCO₃) using rape flower pollen as the template. CaCO₃ adsorbent was characterized using X-ray diffraction (XRD), scanning electronic microscopy (SEM), and Brunner−Emmet−Teller measurements (BET). The equilibrium adsorption data on amoxicillin were explained using Langmuir, Freundlich, and Temkin adsorption isotherm models. The pseudo-first order, second order, pseudo-second order, and intra-particle diffusion kinetic models were used to explore adsorption kinetics. Equilibrium adsorption of as-prepared CaCO₃ was better depicted using the Langmuir adsorption model with an R² of 0.9948. The separation factor (R_L) was found to be in the range of 0 < R_L < 1, indicating the favorable adsorption of amoxicillin. The adsorption capacity of mesopore CaCO₃ reached 13.49 mg·g⁻¹ in 0.2 g∙L⁻¹ amoxicillin solution. The values of adsorption thermodynamic parameters (ΔH^θ, ΔS^θ, ΔG^θ) were obtained. In addition, the adsorption process turned out to be endothermic and spontaneous for the CaCO₃ product at 298 K, 308 K, and 318 K. Full article

(This article belongs to the Special Issue Nanomineralogy)

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18 pages, 1913 KiB

Open AccessReview

Review on Beneficiation Techniques and Reagents Used for Phosphate Ores

by Yaoyang Ruan, Dongsheng He and Ruan Chi

Minerals 2019, 9(4), 253; https://doi.org/10.3390/min9040253 - 25 Apr 2019

Cited by 83 | Viewed by 12849

Abstract

Phosphate ore is an important raw material for manufacturing fertilizers and phosphorous chemical products. While most of the phosphate resources cannot be directly treated as feed stock due to the low grade of P₂O₅ and high content of impurities. In [...] Read more.

Phosphate ore is an important raw material for manufacturing fertilizers and phosphorous chemical products. While most of the phosphate resources cannot be directly treated as feed stock due to the low grade of P₂O₅ and high content of impurities. In order to obtain a qualified phosphate concentrate, the beneficiation of the low-grade phosphate ore is, hence, of great necessity. Many beneficiation techniques can be employed to upgrade the P₂O₅ grade of phosphate ores based on their characteristics in chemical composition and texture. The flotation process is most widely applied to balance the P₂O₅ recovery ratio and cost. In this review, the dominant techniques for the beneficiation of phosphate ores are introduced. Moreover, the factors that affect the flotation of phosphate ore, including the properties of mineralogy, flotation reagents (depressants and collectors) and flotation medium, were systematically analyzed. Full article

(This article belongs to the Special Issue Recent Trends in Phosphate Mining and Beneficiation and Related Waste Management)

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32 pages, 6468 KiB

Open AccessArticle

Metamorphic and Metasomatic Kyanite-Bearing Mineral Assemblages of Thassos Island (Rhodope, Greece)

by Alexandre Tarantola, Panagiotis Voudouris, Aurélien Eglinger, Christophe Scheffer, Kimberly Trebus, Marie Bitte, Benjamin Rondeau, Constantinos Mavrogonatos, Ian Graham, Marius Etienne and Chantal Peiffert

Minerals 2019, 9(4), 252; https://doi.org/10.3390/min9040252 - 25 Apr 2019

Cited by 15 | Viewed by 8806

Abstract

The Trikorfo area (Thassos Island, Rhodope massif, Northern Greece) represents a unique mineralogical locality with Mn-rich minerals including kyanite, andalusite, garnet and epidote. Their vivid colors and large crystal size make them good indicators of gem-quality materials, although crystals found up to now [...] Read more.

The Trikorfo area (Thassos Island, Rhodope massif, Northern Greece) represents a unique mineralogical locality with Mn-rich minerals including kyanite, andalusite, garnet and epidote. Their vivid colors and large crystal size make them good indicators of gem-quality materials, although crystals found up to now are too fractured to be considered as marketable gems. The dominant lithology is represented by a garnet–kyanite–biotite–hematite–plagioclase ± staurolite ± sillimanite paragneiss. Thermodynamic Perple_X modeling indicates conditions of ca. 630–710 °C and 7.8–10.4 kbars. Post-metamorphic metasomatic silicate and calc-silicate (Mn-rich)-minerals are found within (i) green-red horizons with a mineralogical zonation from diopside, hornblende, epidote and grossular, (ii) mica schists containing spessartine, kyanite, andalusite and piemontite, and (iii) weakly deformed quartz-feldspar coarse-grained veins with kyanite at the interface with the metamorphic gneiss. The transition towards brittle conditions is shown by Alpine-type tension gashes, including spessartine–epidote–clinochlore–hornblende-quartz veins, cross-cutting the metamorphic foliation. Kyanite is of particular interest because it is present in the metamorphic paragenesis and locally in metasomatic assemblages with a large variety of colors (zoned blue to green/yellow-transparent and orange). Element analyses and UV-near infrared spectroscopy analyses indicate that the variation in color is due to a combination of Ti⁴⁺–Fe²⁺, Fe³⁺ and Mn³⁺ substitutions with Al³⁺. Structural and mineralogical observations point to a two-stage evolution of the Trikorfo area, where post-metamorphic hydrothermal fluid circulation lead locally to metasomatic reactions from ductile to brittle conditions during Miocene exhumation of the high-grade host-rocks. The large variety of mineral compositions and assemblages points to a local control of the mineralogy and fO₂ conditions during metasomatic reactions and interactions between hydrothermal active fluids and surrounding rocks. Full article

(This article belongs to the Special Issue Mineralogy and Geochemistry of Gems)

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19 pages, 5605 KiB

Open AccessArticle

Formation of Authigenic Low-Magnesium Calcite from Sites SS296 and GC53 of the Gulf of Mexico

by Huiwen Huang, Shanggui Gong, Niu Li, Daniel Birgel, Jörn Peckmann, Meng Jin, Ming Cheng, Harry H. Roberts, Duofu Chen and Dong Feng

Minerals 2019, 9(4), 251; https://doi.org/10.3390/min9040251 - 25 Apr 2019

Cited by 8 | Viewed by 4767

Abstract

Authigenic low-magnesium calcite (LMC)—a mineral phase that should precipitate in calcite seas rather than today’s aragonite sea—was recently discovered at the seafloor of the Gulf of Mexico (GoM) at water depths of 65 m (site SS296) and 189 m (site GC53). This study [...] Read more.

Authigenic low-magnesium calcite (LMC)—a mineral phase that should precipitate in calcite seas rather than today’s aragonite sea—was recently discovered at the seafloor of the Gulf of Mexico (GoM) at water depths of 65 m (site SS296) and 189 m (site GC53). This study investigates the mineralogical, petrographic, and geochemical characteristics of LMC from both sites to reveal its formation process. The δ¹⁸O values of LMC from site SS296 cluster in two groups (−0.6‰ to 1.7‰; 6.3‰ to 7.5‰) and the presence of cone-in-cone texture in the samples with lower δ¹⁸O values suggest precipitation at higher temperatures and greater depth. Low δ¹⁸O values of LMC from site GC53 ranging from −9.4‰ to −2.5‰ indicate an influence of meteoric waters during formation. LMC at both sites reveals a wide range of δ¹³C values (−17.4‰ to 2.6‰), indicating various carbon sources including seawater and/or organic matter. This interpretation is further supported by the δ¹³C values of organic carbon extracted from the LMC lithologies (δ¹³C_org: from −26.8‰ to −18.9‰). Relatively low Sr concentrations of LMC samples regardless of variable ⁸⁷Sr/⁸⁶Sr ratios, ranging from 0.707900 to 0.708498 for site GC53 and from 0.709537 to 0.710537 for site SS396, suggest the exchange of Sr between pore fluids and ambient sediments/rocks. The observed wide range of ⁸⁷Sr/⁸⁶Sr ratios and the enrichment of Fe and Mn in LMC is in accordance with pore fluids deriving from the dissolution of Louann salt. Overall, this study reveals that the formation of LMC at sites SS296 and GC53 was favored by the presence of low Mg/Ca ratio pore fluids resulting from salt dissolution in subsurface environments when sufficient dissolved inorganic carbon was available. These results are essential for understanding the formation of marine LMC at times of an aragonite sea, highlighting the role of formation environments—open environments close to or at the seafloor vs. confined subseafloor environments typified by pore waters with a composition largely different from that of seawater. Full article

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13 pages, 1032 KiB

Open AccessArticle

Accelerating Copper Leaching from Sulfide Ores in Acid-Nitrate-Chloride Media Using Agglomeration and Curing as Pretreatment

by Pía C. Hernández, Junior Dupont, Osvaldo O. Herreros, Yecid P. Jimenez and Cynthia M. Torres

Minerals 2019, 9(4), 250; https://doi.org/10.3390/min9040250 - 25 Apr 2019

Cited by 27 | Viewed by 4845

Abstract

This work investigates the effect of an agglomeration and curing pretreatment on leaching of a copper sulfide ore, mainly chalcopyrite, using mini-columns in acid-nitrate-chloride media. Ten pretreatment tests were conducted to evaluate different variables, namely the addition of nitrate as NaNO₃ (11.7 [...] Read more.

This work investigates the effect of an agglomeration and curing pretreatment on leaching of a copper sulfide ore, mainly chalcopyrite, using mini-columns in acid-nitrate-chloride media. Ten pretreatment tests were conducted to evaluate different variables, namely the addition of nitrate as NaNO₃ (11.7 and 23.3 kg/ton), chloride as NaCl (2.1 and 19.8 kg/ton), curing time (20 and 30 days) and repose temperature (25 and 45 °C). The optimum copper extraction of 58.6% was achieved with the addition of 23.3 kg of NaNO₃/ton, 19.8 kg of NaCl/ton, and after 30 days of curing at 45 °C. Under these pretreatment conditions, three samples of ore were leached in mini-columns. The studied parameters were temperature (25 and 45 °C) and chloride concentration (20 and 40 g/L). The optimum copper extraction of 63.9% was obtained in the mini-column leaching test at 25 °C, with the use of 20 g/L of chloride. A higher temperature (45 °C) and a higher chloride concentration (40 g/L) negatively affected the extraction. The pretreatment stage had favorable effects, in terms of accelerating copper dissolution and improving leaching of copper sulfide ore in acid-nitrate-chloride media. Waste salts from caliche industry and waste brine from reverse osmosis can be used for providing the nitrate and chloride media. Full article

(This article belongs to the Special Issue Recent Advances in Hydro- and Biohydrometallurgy)

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Graphical abstract

20 pages, 4332 KiB

Open AccessArticle

The Thermal and Dynamic Process of Core → Mantle → Crust and the Metallogenesis of Guojiadian Mantle Branch in Northwestern Jiaodong

by Shuyin Niu, Chao Chen, Jianzhen Zhang, Fuxiang Zhang, Fengxiang Wang and Aiqun Sun

Minerals 2019, 9(4), 249; https://doi.org/10.3390/min9040249 - 24 Apr 2019

Cited by 6 | Viewed by 2761

Abstract

The Jiaodong gold mineral province, with an overall endowment estimated as >3000 t, located at the eastern segment of the North China Craton (NCC), ranks as the greatest source of Au in China. The structural evolution, magmatic activity and metallogenesis during the Mesozoic [...] Read more.

The Jiaodong gold mineral province, with an overall endowment estimated as >3000 t, located at the eastern segment of the North China Craton (NCC), ranks as the greatest source of Au in China. The structural evolution, magmatic activity and metallogenesis during the Mesozoic played important roles in the large scale regional gold, silver and polymetallic mineralization in this area; among them, the intensive activation of fault structures is the most important factor for metallogenesis. This study takes the regional deep faults as main thread to discuss the controlling role of faults in large scale metallogenesis. The Jiaojia fault and Sanshandao faults in the northwest margin of the Guojiadian mantle branch not only are dominant migration channels for hydrothermal fluid but are very important favorable spaces for ore-forming and ore-hosting during the formation of world-class super large gold deposits in this area. The deep metallogenic process can be summarized as involving intensive Earth’s core, mantle and crust activity → magmatism → uplifting of metamorphic complex → detachment of cover rocks → formation of mantle branch → penetration of hydrothermal fluid along deep faults → concentration of metallogenic materials → formation of super large deposits. Full article

(This article belongs to the Special Issue Polymetallic Metallogenic System)

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13 pages, 3596 KiB

Open AccessFeature PaperArticle

Tsikourasite, Mo₃Ni₂P_1+x (x < 0.25), a New Phosphide from the Chromitite of the Othrys Ophiolite, Greece

by Federica Zaccarini, Luca Bindi, Elena Ifandi, Tassos Grammatikopoulos, Chris Stanley, Giorgio Garuti and Daniela Mauro

Minerals 2019, 9(4), 248; https://doi.org/10.3390/min9040248 - 24 Apr 2019

Cited by 11 | Viewed by 6089

Abstract

Tsikourasite, Mo₃Ni₂P_1+x (x < 0.25), is a new phosphide discovered in a mantle-hosted podiform chromitite collected in the abandoned mine of Agios Stefanos (Othrys ophiolite), Central Greece. It forms tiny grains (from a few μm up [...] Read more.

Tsikourasite, Mo₃Ni₂P_1+x (x < 0.25), is a new phosphide discovered in a mantle-hosted podiform chromitite collected in the abandoned mine of Agios Stefanos (Othrys ophiolite), Central Greece. It forms tiny grains (from a few μm up to about 80 μm) and occurs as isolated grains or associated with other known minerals such as nickelphosphide and awaruite, and with undetermined minerals such as Ni-allabogdanite or Ni-barringerite and a V-sulphide. Tsikourasite is brittle and has a metallic luster. In plane-polarized light, tsikourasite is white yellow and it shows no bireflectance, anisotropism or pleochroism. Internal reflections were not observed, Reflectance values of tsikourasite in air (R in %) are: 55.7 at 470 nm, 56.8 at 546 nm, 57.5 at 589 nm and 58.5 at 650 nm. Five spot analyses of tsikourasite give the average composition: P 7.97, S 0.67, V 14.13, Fe 14.37, Co 7.59, Ni 23.9, and Mo 44.16, total 99.60 wt.%, corresponding to the empirical formula (Mo_1.778V_1.071Fe_0.082Co_0.069)_Σ3.000(Ni_1.572Co_0.428)_Σ2.000(P_0.981S_0.079)_Σ1.060, on the basis of Σ(Mo +V + Fe + Co + Ni) = 5 apfu and taking into account the structural results. The simplified formula is Mo₃Ni₂P_1+x (x < 0.25). The density, which was calculated based on the empirical formula and single-crystal data, is 9.182 g/cm³. The mineral is cubic, space group F-43m, with a = 10.8215(5) Å and Z = 16. Although tsikourasite is similar in composition to those of monipite (MoNiP), polekhovskyite (MoNiP₂), and the synthetic compound MoNiP₂, all these phases are hexagonal and not cubic like tsikourasite. It exhibits the same structure as the cubic Mo₃Ni₂P_1.18 compound [space group F-43m, a = 10.846(2) Å] synthesized at 1350 °C. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (No. 2018-156). The mineral honors Professor Basilios Tsikouras of the Universiti Brunei Darussalam. Full article

(This article belongs to the Collection New Minerals)

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13 pages, 7299 KiB

Open AccessArticle

A Geostatistical Simulation of a Mineral Deposit using Uncertain Experimental Data

by João Narciso, Cristina Paixão Araújo, Leonardo Azevedo, Ruben Nunes, João Filipe Costa and Amílcar Soares

Minerals 2019, 9(4), 247; https://doi.org/10.3390/min9040247 - 23 Apr 2019

Cited by 5 | Viewed by 3214

Abstract

In the geostatistical modeling and characterization of natural resources, the traditional approach for determining the spatial distribution of a given deposit using stochastic sequential simulation is to use the existing experimental data (i.e., direct measurements) of the property of interest as if there [...] Read more.

In the geostatistical modeling and characterization of natural resources, the traditional approach for determining the spatial distribution of a given deposit using stochastic sequential simulation is to use the existing experimental data (i.e., direct measurements) of the property of interest as if there is no uncertainty involved in the data. However, any measurement is prone to error from different sources, for example from the equipment, the sampling method, or the human factor. It is also common to have distinct measurements for the same property with different levels of resolution and uncertainty. There is a need to assess the uncertainty associated with the experimental data and integrate it during the modeling procedure. This process is not straightforward and is often overlooked. For the reliable modeling and characterization of a given ore deposit, measurement uncertainties should be included as an intrinsic part of the geo-modeling procedure. This work proposes the use of a geostatistical simulation algorithm to integrate uncertain experimental data through the use of stochastic sequential simulations with local probability functions. The methodology is applied to the stochastic modeling of a benchmark mineral deposit, where certain and uncertain experimental data co-exist. The uncertain data is modeled by assigning individual probability distribution functions to each sample location. Different strategies are proposed to build these local probability distributions. Each scenario represents variable degrees of uncertainty. The impacts of the different modeling approaches on the final deposit model are discussed. The resulting models of these proposed scenarios are also compared against those retrieved from previous studies that use conventional geostatistical simulation. The results from the proposed approaches showed that using stochastic sequential simulation with local probability functions to represent local uncertainties decreased the estimation error of the resulting model, producing fewer misclassified ore blocks. Full article

(This article belongs to the Section Mineral Deposits)

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14 pages, 4117 KiB

Open AccessArticle

Influence of Impurity Dissolution on Surface Properties and NH₃-SCR Catalytic Activity of Rare Earth Concentrate

by Kai Zhang, Jinhao Zhu, Shuning Zhang, Na Li, Huijuan Luo, Baowei Li, Zengwu Zhao, Guang Jin and Wenfei Wu

Minerals 2019, 9(4), 246; https://doi.org/10.3390/min9040246 - 22 Apr 2019

Cited by 7 | Viewed by 2798

Abstract

Impurity removal and modification of rare earth concentrate powder were conducted by roasting weak acid-weak alkali leaching to obtain the active components of denitrification catalysts. NH₃ selective catalytic reduction catalyst samples were prepared by mixing and kneading with pseudo-γ-Al₂O₃ [...] Read more.

Impurity removal and modification of rare earth concentrate powder were conducted by roasting weak acid-weak alkali leaching to obtain the active components of denitrification catalysts. NH₃ selective catalytic reduction catalyst samples were prepared by mixing and kneading with pseudo-γ-Al₂O₃ boehmite as carrier. The results showed that the Ce₇O₁₂ content in the active component samples increased and dispersed more evenly. The grain size of the samples was refined, the specific surface area increased, and the active sites exposed more. Ce coexists in the form of Ce³⁺ and Ce⁴⁺. Fe coexists in the form of Fe³⁺ and Fe²⁺, but Fe³⁺ is abundant. Some Ce, La, Nd, Pr, Fe, Mn, and other components formed solid melts during preparation, which increased the synergistic catalytic effect. The denitrification efficiency of the catalyst sample was 92.8% under the conditions of reaction temperature 400 °C, NO content was 600 ppm, NH₃/NO ratio was 1.5, and O₂ concentration was 4%. Full article

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

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18 pages, 3584 KiB

Open AccessArticle

Volatile Chalcophile Elements in Native Sulfur from a Submarine Hydrothermal System at Kueishantao, Offshore NE Taiwan

by Ming-Zhen Yu, Xue-Gang Chen, Dieter Garbe-Schönberg, Ying Ye and Chen-Tung Arthur Chen

Minerals 2019, 9(4), 245; https://doi.org/10.3390/min9040245 - 21 Apr 2019

Cited by 9 | Viewed by 3396

Abstract

We analyzed sulfur isotopes, trace elements and chalcophile elements (Se, Te, As, Sb, and Hg) in the native sulfur matrix from the Kueishantao hydrothermal system and conducted a systematic micro-analytical investigation. The sulfur matrix lacked all measured metals (e.g., Fe, Cu) and rare [...] Read more.

We analyzed sulfur isotopes, trace elements and chalcophile elements (Se, Te, As, Sb, and Hg) in the native sulfur matrix from the Kueishantao hydrothermal system and conducted a systematic micro-analytical investigation. The sulfur matrix lacked all measured metals (e.g., Fe, Cu) and rare earth elements (REEs) while being significantly enriched in Te, As, Se (750–1500 ppm), Sb (around 100 ppm) and some Hg. The δ³⁴S data (0.2–2.4‰) suggest a magmatic source leached from igneous rocks and a small contribution of seawater sulfates to the sulfur in hydrothermal deposits. Correlations between Te, As, Sb, and S (r² = 0.30–0.61) indicate that these elements behave coherently in magmatic-hydrothermal processes. The enrichment factors and content ratios of these elements demonstrate their abundance in the sulfur matrix and minor fractionation after being partitioned into the metallic melt and forming a separate vapor phase to transport. Our study focuses on the native sulfur matrix in a shallow-water volcanic hydrothermal system, to which relatively little attention has previously been paid. This will expand our understanding of hydrothermal precipitates. The study of volatile chalcophile elements in the matrix will provide significant information about their sources, distributions and other geochemical behaviors in magmatic-hydrothermal processes and help to understand the Kueishantao hydrothermal circulation better. Full article

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26 pages, 12713 KiB

Open AccessArticle

Mineralogy of Zirconium in Iron-Oxides: A Micron- to Nanoscale Study of Hematite Ore from Peculiar Knob, South Australia

by William Keyser, Cristiana L. Ciobanu, Nigel J. Cook, Holly Feltus, Geoff Johnson, Ashley Slattery, Benjamin P. Wade and Kathy Ehrig

Minerals 2019, 9(4), 244; https://doi.org/10.3390/min9040244 - 19 Apr 2019

Cited by 9 | Viewed by 4996

Abstract

Zirconium is an element of considerable petrogenetic significance but is rarely found in hematite at concentrations higher than a few parts-per-million (ppm). Coarse-grained hematite ore from the metamorphosed Peculiar Knob iron deposit, South Australia, contains anomalous concentrations of Zr and has been investigated [...] Read more.

Zirconium is an element of considerable petrogenetic significance but is rarely found in hematite at concentrations higher than a few parts-per-million (ppm). Coarse-grained hematite ore from the metamorphosed Peculiar Knob iron deposit, South Australia, contains anomalous concentrations of Zr and has been investigated using microanalytical techniques that can bridge the micron- to nanoscales to understand the distribution of Zr in the ore. Hematite displays textures attributable to annealing under conditions of high-grade metamorphism, deformation twins (r~85° to hematite elongation), relict magnetite and fields of sub-micron-wide inclusions of baddeleyite as conjugate needles with orientation at ~110°/70°. Skeletal and granoblastic zircon, containing only a few ppm U, are both present interstitial to hematite. Using laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) spot analysis and mapping, the concentration of Zr in hematite is determined to be ~260 ppm on average (up to 680 ppm). The Zr content is, however, directly attributable to nm-scale inclusions of baddeleyite pervasively distributed throughout the hematite rather than Zr in solid solution. Distinction between nm-scale inclusions and lattice-bound trace element substitutions cannot be made from LA-ICP-MS data alone and requires nanoscale characterization. Scandium-rich (up to 0.18 wt. % Sc₂O₃) cores in zircon are documented by microprobe analysis and mapping. Using high-angle annular dark field scanning transmission electron microscopy imaging (HAADF-STEM) and energy-dispersive spectrometry STEM mapping of foils prepared in-situ by focused ion beam methods, we identify [

0 \bar{1} 1

]_baddeleyite epitaxially intergrown with [

2 \bar{2} .1

]_hematite. Lattice vectors at 84–86° underpinning the epitaxial intergrowth orientation correspond to directions of r-twins but not to the orientation of the needles, which display a ~15° misfit. This is attributable to directions of trellis exsolutions in a precursor titanomagnetite. U–Pb dating of zircon gives a ²⁰⁶Pb/²³⁸U weighted mean age of 1741 ± 49 Ma (sensitive high-resolution ion microprobe U–Pb method). Based on the findings presented here, detrital titanomagnetite from erosion of mafic rocks is considered the most likely source for Zr, Ti, Cr and Sc. Whether such detrital horizons accumulated in a basin with chemical precipitation of Fe-minerals (banded iron formation) is debatable, but such Fe-rich sediments clearly included detrital horizons. Martitization during the diagenesis-supergene enrichment cycle was followed by high-grade metamorphism during the ~1.73–1.69 Ga Kimban Orogeny during which martite recrystallized as granoblastic hematite. Later interaction with hydrothermal fluids associated with ~1.6 Ga Hiltaba-granitoids led to W, Sn and Sb enrichment in the hematite. By reconstructing the evolution of the massive orebody at Peculiar Knob, we show how application of complimentary advanced microanalytical techniques, in-situ and on the same material but at different scales, provides critical constraints on ore-forming processes. Full article

(This article belongs to the Special Issue Minerals Down to the Nanoscale: A Glimpse at Ore-Forming Processes)

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17 pages, 4154 KiB

Open AccessArticle

Mineralogy and Garnet Sm–Nd Dating for the Hongshan Skarn Deposit in the Zhongdian Area, SW China

by Bo Zu, Chunji Xue, Chen Dong and Yi Zhao

Minerals 2019, 9(4), 243; https://doi.org/10.3390/min9040243 - 19 Apr 2019

Cited by 6 | Viewed by 3088

Abstract

The Hongshan deposit is one of the largest Cu-polymetallic deposits in the Zhongdian area, southwest China. Two types of Cu–Mo ores, mainly developed in the skarns, have been recognized in the Hongshan deposit, i.e., massive or layered skarn and vein-type, with the former [...] Read more.

The Hongshan deposit is one of the largest Cu-polymetallic deposits in the Zhongdian area, southwest China. Two types of Cu–Mo ores, mainly developed in the skarns, have been recognized in the Hongshan deposit, i.e., massive or layered skarn and vein-type, with the former being dominant. The highly andraditic composition of garnet (Adr₁₀₀ to Adr₆₄Gr₃₂) and diopsidic composition of pyroxene (Di₉₀Hd₉ to Di₁Hd₉₉) indicate the layered skarn ores are of magmatic-hydrothermal origin that formed under oxidized conditions. Sm–Nd dating of garnet yield a well-constrained isochron age of 76.48 ± 7.29 Ma (MSWD = 1.2) for the layered skarn ores. This age was consistent with the Re–Os age for the pyrrhotite from the layered skarn ores, and thereby indicated that the layered skarn mineralization was formed in the Late Cretaceous, rather than in the Triassic as was previously thought. The coincidence of the geochronology from the layered skarn ores and vein-type mineralization further indicated that both ores were the result of a single genetic event, rather than multiple events. The recognition of the Late Cretaceous post-collisional porphyry–skarn Cu–Mo–W belt in the Zhongdian area exhibited a promising prospecting potential. Full article

(This article belongs to the Special Issue Polymetallic Metallogenic System)

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17 pages, 6603 KiB

Open AccessArticle

Fractal Characteristics and Heterogeneity of the Nanopore Structure of Marine Shale in Southern North China

by Kun Yu, Yiwen Ju, Yu Qi, Peng Qiao, Cheng Huang, Hongjian Zhu and Hongye Feng

Minerals 2019, 9(4), 242; https://doi.org/10.3390/min9040242 - 19 Apr 2019

Cited by 23 | Viewed by 3443

Abstract

The characteristics of the nanopore structure in shale play a crucial role in methane adsorption and in determining the occurrence and migration of shale gas. In this study, using an integrated approach of X-ray diffraction (XRD), N₂ adsorption, and field emission scanning [...] Read more.

The characteristics of the nanopore structure in shale play a crucial role in methane adsorption and in determining the occurrence and migration of shale gas. In this study, using an integrated approach of X-ray diffraction (XRD), N₂ adsorption, and field emission scanning electron microscopy (FE-SEM), we systematically focused on eight drilling samples of marine Taiyuan shale from well ZK1 in southern North China to study the characteristics and heterogeneity of their nanopore structure. The results indicated that different sedimentary environments may control the precipitation of clay and quartz between transitional shale and marine shale, leading to different organic matter (OM)–clay relationships and different correlations between total organic carbon (TOC) and mineral content. The shale with high TOC content tended to have more heterogeneous micropores, leading to a higher fractal dimension and a more complex nanopore structure. With the increase of TOC content and thermal evolution of OM, the heterogeneity of the pore structure became more significant. Quartz from marine shale possessed abundant macropores, resulting in a decrease of the Brunauere–Emmette–Teller (BET) surface area (SA) and an increase of the average pore size (APS), while clay minerals developed a large number of micropores which worked together with OM to influence the nanopore structure of shale, leading to the increase of the SA and the decrease of the APS. The spatial order of interlayer pores increased with the increase of mixed-layer illite–smectite (MLIS) content, which naturally reduced the fractal dimensions. In contrast, kaolinite, chlorite, and illite have a small number of nanopores, which might enhance the complexity and reduce the connectivity of the nanopore system by mean of pore-blocking. Taiyuan shale with higher heterogeneity is highly fractal, and its fractal dimensions are principally related to the micropores. The fractal dimensions correlate positively with the SA and total pore volume, suggesting that marine shale with higher heterogeneity may possess a larger SA and a higher total pore volume. Full article

(This article belongs to the Special Issue Nanomineralogy)

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19 pages, 37143 KiB

Open AccessArticle

Multi-Analysis Characterisation of a Vernacular House in Doha (Qatar): Petrography and Petrophysics of its Construction Materials

by David Martín Freire-Lista, Gizem Kahraman and Robert Carter

Minerals 2019, 9(4), 241; https://doi.org/10.3390/min9040241 - 18 Apr 2019

Cited by 4 | Viewed by 4835

Abstract

This study characterises the original construction materials (building stones and mortars) of a collapsed two-storey colonnaded structure in the Ismail Mandani house, located in the old city centre of Doha (Qatar). Results were drawn based on interpretation and integration of historical, in situ [...] Read more.

This study characterises the original construction materials (building stones and mortars) of a collapsed two-storey colonnaded structure in the Ismail Mandani house, located in the old city centre of Doha (Qatar). Results were drawn based on interpretation and integration of historical, in situ observations and analytical data. The mortars and stones were characterised following a multidisciplinary approach, combining macroscopic observation with petrographic microscopy, mineralogical analysis (X-ray diffraction) and elemental analysis (handheld X-ray fluorescence) of samples. Moreover, hydric properties, ultrasonic pulse velocity and colour of representative samples of the house were studied. The results revealed the use of two types of stones and three different types of gypsum mortars. The original construction materials came from nearby coastal stones. Gypsum of the most used mortar had a calcination temperature between 120 and 160 °C and its colour was produced by lumps with higher Fe content. The materials’ effective porosity and water absorption were high, and their ultrasonic pulse velocity was low. These petrophysical results indicated they had low quality for construction purposes. The composition and colour of the original construction materials were quantified, which will allow the reproduction of their aesthetic characteristics and improvement of their quality in future reconstruction works. Full article

(This article belongs to the Special Issue Petrography of Construction Materials: Compositional, Mineralogical and Textural Features)

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14 pages, 3185 KiB

Open AccessArticle

Effect of High Mixing Intensity on Rheological Properties of Cemented Paste Backfill

by Liuhua Yang, Hongjiang Wang, Hong Li and Xu Zhou

Minerals 2019, 9(4), 240; https://doi.org/10.3390/min9040240 - 18 Apr 2019

Cited by 26 | Viewed by 4456

Abstract

Cemented paste backfill (CPB) consists of a mixture of fine particles, mainly consisting of tailings and cement dispersed in water. Therefore, it is necessary to introduce an intensive shearing force into the paste during mixing in order to maintain an equilibrium between agglomeration [...] Read more.

Cemented paste backfill (CPB) consists of a mixture of fine particles, mainly consisting of tailings and cement dispersed in water. Therefore, it is necessary to introduce an intensive shearing force into the paste during mixing in order to maintain an equilibrium between agglomeration and dispersion. It is influential for the macroscopical fluidity and rheological properties when changes occur in the microstructure of CPB under shear. However, the research on how mixing affects the properties of CPB is still in its infancy. This paper puts an insight into the relation between the mixing intensity and the rheological behavior of the CPB. It can be demonstrated that two threshold mixing intensities exist in this process. After passing the first or lower threshold, the rheological parameters (yield stress and viscosity) of the paste decrease. After passing the second threshold, a continued increase is observed. The changes in rheological properties are connected with physical and chemical changes in the microstructure of the CPB. The results are discussed in light of the three concepts “structural breakdown”, “thixotropic breakdown”, and “thixotropic behavior” of rheological properties of CPB. Full article

(This article belongs to the Special Issue Towards a Sustainable Management of Mine Wastes: Reprocessing, Reuse, Revalorization and Repository)

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20 pages, 5164 KiB

Open AccessArticle

Experiments on Rare-Earth Element Extractions from Umber Ores for Optimizing the Grinding Process

by Yutaro Takaya, Meiqi Wang, Koichiro Fujinaga, Etsuo Uchida, Tatsuo Nozaki and Yasuhiro Kato

Minerals 2019, 9(4), 239; https://doi.org/10.3390/min9040239 - 17 Apr 2019

Cited by 3 | Viewed by 3424

Abstract

Ancient hydrothermal metalliferous sediments (umber) have recently attracted attention as a new rare-earth element resource. We conducted chemical leaching experiments on three different umber ores to optimize the hydrometallurgical extraction process, especially regarding the grinding process. The three umber ore samples, which were [...] Read more.

Ancient hydrothermal metalliferous sediments (umber) have recently attracted attention as a new rare-earth element resource. We conducted chemical leaching experiments on three different umber ores to optimize the hydrometallurgical extraction process, especially regarding the grinding process. The three umber ore samples, which were collected from Japanese accretionary complexes (Kuminiyama and Aki umber) and Troodos ophiolite (Cyprus umber), had different chemical, mineral, and physical properties, and showed different leaching behaviors. The experimental results revealed that the physical properties (density and P-wave propagation velocity) principally controlled the extent of REY (lanthanides and yttrium) extraction from the umber ore samples, and REY extraction from umber samples clearly increased with the decrease in the density and P-wave propagation velocity. The differences in physical properties of the umber samples are attributable to the pressure and thermal history of each ore sample, and it was revealed that umber samples which underwent strong metamorphism are not suitable for actual development. The results also suggested that the optimum particle size (optimum grinding level) of umber samples is simply predictable based on the physical properties. The results of this study should be valuable for future efforts to procure these important mineral resources. Full article

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

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38 pages, 4201 KiB

Open AccessArticle

Integrating the Theory of Sampling into Underground Mine Grade Control Strategies: Case Studies from Gold Operations

by Simon C. Dominy, Hylke J. Glass, Louisa O’Connor, Chloe K. Lam and Saranchimeg Purevgerel

Minerals 2019, 9(4), 238; https://doi.org/10.3390/min9040238 - 17 Apr 2019

Cited by 3 | Viewed by 7489

Abstract

Grade control aims to deliver adequately defined tonnes of ore to the process plant. The foundation of any grade control programme is collecting high-quality samples within a geological context. The requirement for quality samples has long been recognised, in that these should be [...] Read more.

Grade control aims to deliver adequately defined tonnes of ore to the process plant. The foundation of any grade control programme is collecting high-quality samples within a geological context. The requirement for quality samples has long been recognised, in that these should be representative and fit-for-purpose. Correct application of the Theory of Sampling reduces sampling errors across the grade control process, in which errors can propagate from sample collection through sample preparation to assay results. This contribution presents three case studies which are based on coarse gold-dominated orebodies. These illustrate the challenges and potential solutions to achieve representative sampling and build on the content of a previous publication. Solutions ranging from bulk samples processed through a plant to whole-core sampling and assaying using bulk leaching, are discussed. These approaches account for the nature of the mineralisation, where extreme gold particle-clustering effects render the analysis of small-scale samples highly unrepresentative. Furthermore, the analysis of chip samples, which generally yield a positive bias due to over-sampling of quartz vein material, is discussed. Full article

(This article belongs to the Special Issue Sampling Across the Mine Value Chain)

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15 pages, 2188 KiB

Open AccessArticle

Valorization of Phosphate Mine Waste Rocks as Materials for Road Construction

by Mustapha Amrani, Yassine Taha, Azzouz Kchikach, Mostafa Benzaazoua and Rachid Hakkou

Minerals 2019, 9(4), 237; https://doi.org/10.3390/min9040237 - 17 Apr 2019

Cited by 44 | Viewed by 6506

Abstract

The road construction sector is a worldwide high consumer of natural aggregates. The use of unusual industrial by-products in road techniques can contribute to the conservation of non-renewable natural resources and the reduction of wastes produced by some industries. Phosphate waste rocks could [...] Read more.

The road construction sector is a worldwide high consumer of natural aggregates. The use of unusual industrial by-products in road techniques can contribute to the conservation of non-renewable natural resources and the reduction of wastes produced by some industries. Phosphate waste rocks could be considered as potential alternative secondary raw materials in road construction. The use and valorization of these wastes is currently limited according to the Moroccan guide for road earthworks (GMTR). The guide has classified these materials as waste products, which consequently, cannot be used in road construction. However, phosphate waste rocks are sedimentary natural rocks which have not been subjected to any transformation other than mechanical fragmentation. The goal of this paper is to discuss key-properties of various phosphate mine waste rocks (PMWR) to be used as road materials. Samples were taken from different stockpiles in the phosphate mine site of Gantour in Morocco. The different waste rocks samples were characterized in terms of their physical, geotechnical, chemical, mineralogical and environmental properties using international testing norms. The obtained results showed that the studied PMWR presented satisfying characteristics; the specific (particle) density: ρs > 26 kN/m³, Los Angeles abrasion: 45% < LA < 58%), methylene blue value MBV < 1 g/100g, organic matter: OM < 1% and plasticity index: PI < 20%. All PMWR were confirmed as possessing the requested geotechnical properties to be used as materials for embankments. Moreover, leaching tests showed that none of them released any contaminants. In field application, these materials have been also successfully used in in situ experimental pilot testing. Therefore, the PMWR have to be classified in the category of natural aggregates that are similar to conventional materials. Full article

(This article belongs to the Special Issue Recent Trends in Phosphate Mining and Beneficiation and Related Waste Management)

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13 pages, 924 KiB

Open AccessArticle

Optimizing Conditions for Scandium Extraction from Bauxite Residue Using Taguchi Methodology

by Theopisti Lymperopoulou, Paraskevas Georgiou, Lamprini-Areti Tsakanika, Konstantinos Hatzilyberis and Maria Ochsenkuehn-Petropoulou

Minerals 2019, 9(4), 236; https://doi.org/10.3390/min9040236 - 17 Apr 2019

Cited by 21 | Viewed by 4149

Abstract

Bauxite residue is the voluminous by-product of alumina production after Bayer process. Its high alkalinity causes disposal problems and harmful environmental impacts. However, the residue contains significant amounts of valuable elements, such as rare earth elements, including scandium. Greek bauxite residue contains a [...] Read more.

Bauxite residue is the voluminous by-product of alumina production after Bayer process. Its high alkalinity causes disposal problems and harmful environmental impacts. However, the residue contains significant amounts of valuable elements, such as rare earth elements, including scandium. Greek bauxite residue contains a high amount of scandium close to its main resources. Taking into account scandium’s limited availability coupled with its high demand in modern technology, bauxite residue could be considered as a potential resource for scandium recovery. In this study, the optimization of scandium extraction from bauxite residue with sulfuric acid is investigated using Taguchi methodology. Based on previous studies, acid molarity, leaching time, solid/liquid ratio, and reaction temperature were selected as control parameters for the selective Sc recovery. Method optimization targeted the highest concentration of scandium combined with the lowest concentration of iron without taking into account application constraints. Maximization of scandium concentration can be achieved only by reduced selectivity. The predicted values resulted from the Taguchi methodology were affirmed by a confirmation experiment conducted at optimal conditions. Regression analysis provided the respective equations to be applied on several conditions, depending on different applications. Full article

(This article belongs to the Special Issue High-Tech Metals Distribution in Bauxites: From the Ore Genesis to the Bayer Process Residue)

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17 pages, 6626 KiB

Open AccessArticle

Source of the Chaoyangzhai Gold Deposit, Southeast Guizhou: Constraints from LA-ICP-MS Zircon U–Pb Dating, Whole-rock Geochemistry and In Situ Sulfur Isotopes

by Hinyuen Tsang, Jingya Cao and Xiaoyong Yang

Minerals 2019, 9(4), 235; https://doi.org/10.3390/min9040235 - 16 Apr 2019

Cited by 4 | Viewed by 3494

Abstract

The Chaoyangzhai gold deposit is one of the newly discovered medium to large scale turbidite-hosted gold deposits in Southeast Guizhou, South China. In this study, laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) zircon U–Pb dating on the tuffaceous- and sandy-slates of Qingshuijiang Formation, Xiajiang [...] Read more.

The Chaoyangzhai gold deposit is one of the newly discovered medium to large scale turbidite-hosted gold deposits in Southeast Guizhou, South China. In this study, laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) zircon U–Pb dating on the tuffaceous- and sandy-slates of Qingshuijiang Formation, Xiajiang Group, and gold-bearing quartz vein yielded similar age distributions, indicating that zircon grains in gold-bearing quartz vein originated from the surrounding tuffaceous- and sandy-slates. In addition, the youngest weighted mean ages of the zircon grains from the tuffaceous- and sandy-slates were 775 ± 13 Ma and 777 ± 16 Ma, respectively, displaying that the tuffaceous- and sandy-slates of the Qingshuijiang Formation were likely deposited in Neoproterozoic. Based on their major and trace element compositions, the tuffaceous- and sandy-slates were sourced from a felsic igneous provenance. The sandy slates have higher contents of Au (mostly ranging from 0.019 to 0.252 ppm), than those of the tuffaceous slates (mostly lower than 0.005 ppm). The δ³⁴S_V-CDT values of pyrite and arsenopyrite of the gold-bearing samples range from +8.12‰ to +9.99‰ and from +9.78 to +10.78‰, respectively, indicating that the sulfur source was from the metamorphic rocks. Together with the evidence of similar geochemical patterns between the tuffaceous- and sandy-slates and gold-bearing quartz, it is proposed that the gold might be mainly sourced from sandy slates. The metamorphic devolatilization, which was caused by the Caledonian orogeny (Xuefeng Orogenic Event), resulted in the formation of the ore-forming fluid. Gold was likely deposited in the fractures due to changes of the physico-chemical conditions, leading to the formation of the Chaoyangzhai gold deposit, and the large-scale gold mineralization in Southeast Guizhou. Full article

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

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25 pages, 11696 KiB

Open AccessArticle

Corundum Anorthosites-Kyshtymites from the South Urals, Russia: A Combined Mineralogical, Geochemical, and U-Pb Zircon Geochronological Study

by Maria I. Filina, Elena S. Sorokina, Roman Botcharnikov, Stefanos Karampelas, Mikhail A. Rassomakhin, Natalia N. Kononkova, Anatoly G. Nikolaev, Jasper Berndt and Wolfgang Hofmeister

Minerals 2019, 9(4), 234; https://doi.org/10.3390/min9040234 - 16 Apr 2019

Cited by 7 | Viewed by 5193

Abstract

Kyshtymites are the unique corundum-blue sapphire-bearing variety of anorthosites of debatable geological origin found in the Ilmenogorsky-Vishnevogorsky complex (IVC) in the South Urals, Russia. Their mineral association includes corundum-sapphire, plagioclase (An_61–93), muscovite, clinochlore, and clinozoisite. Zircon, churchite-(Y), monazite-(Ce), and apatite group [...] Read more.

Kyshtymites are the unique corundum-blue sapphire-bearing variety of anorthosites of debatable geological origin found in the Ilmenogorsky-Vishnevogorsky complex (IVC) in the South Urals, Russia. Their mineral association includes corundum-sapphire, plagioclase (An_61–93), muscovite, clinochlore, and clinozoisite. Zircon, churchite-(Y), monazite-(Ce), and apatite group minerals are found as accessory phases. Besides, churchite-(Y) and zircon are also identified as syngenetic solid inclusions within the sapphires. In situ Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U-Pb zircon geochronology showed the ages at about 290–330 Ma linked to the Hercynian orogeny in IVC. These ages are close to those of the syenitic and carbonatitic magmas of the IVC, pointing to their syngenetic origin, which is in agreement with the trace element geochemistry of the zircons demonstrating clear magmatic signature. However, the trace element composition of sapphires shows mostly metamorphic signature with metasomatic overprints in contrast to the geochemistry of zircons. The reason for this discrepancy can be the fact that the discrimination diagrams for sapphires are not as universal as assumed. Hence, they cannot provide an unambiguous determination of sapphire origin. If it is true and zircons can be used as traces of anorthosite genesis, then it can be suggested that kyshtymites are formed in a magmatic process at 440–420 Ma ago, most probably as plagioclase cumulates in a magma chamber. This cumulate rock was affected by a second magmatic event at 290–330 Ma as recorded in zircon and sapphire zoning. On the other hand, Ti-in-zircon thermometer indicates that processes operated at relatively lower temperature (<900 °C), which is not enough to re-melt the anorthosites. Hence, zircons in kyshtymites can be magmatic but inherited from another rock, which was re-worked during metamorphism. The most probable candidate for the anorthosite protolith is carbonatites assuming that metamorphic fluids could likely leave Al- and Si-rich residue, but removed Ca and CO₂. Further, Si is consumed by the silicification of ultramafic host rocks. However, kyshtymites do not show clear evidence of pronounced metasomatic zonation and evidence for large volume changes due to metamorphic alteration of carbonatites. Thus, the obtained data still do not allow for univocal reconstruction of the kyshtymite origin and further investigations are required. Full article

(This article belongs to the Special Issue Mineralogy and Geochemistry of Gems)

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16 pages, 3806 KiB

Open AccessArticle

Formation Conditions and ⁴⁰Ar/³⁹Ar Age of the Gem-Bearing Boqueirão Granitic Pegmatite, Parelhas, Rio Grande do Norte, Brazil

by Sabina Strmić Palinkaš, Ladislav Palinkaš, Franz Neubauer, Ricardo Scholz, Sibila Borojević Šoštarić and Vladimir Bermanec

Minerals 2019, 9(4), 233; https://doi.org/10.3390/min9040233 - 15 Apr 2019

Cited by 3 | Viewed by 4068

Abstract

The Boqueirão granitic pegmatite, alias Alto da Cabeça pegmatite, is situated in Borborema Pegmatitic Province (BPP) in Northeast Brazil. This pegmatitic province hosts globally important reserves of tantalum and beryllium, as well as significant quantities of gemstones, including aquamarine, morganite, and the high-quality [...] Read more.

The Boqueirão granitic pegmatite, alias Alto da Cabeça pegmatite, is situated in Borborema Pegmatitic Province (BPP) in Northeast Brazil. This pegmatitic province hosts globally important reserves of tantalum and beryllium, as well as significant quantities of gemstones, including aquamarine, morganite, and the high-quality turquoise-blue “Paraíba Elbaite”. The studied lithium-cesium-tantalum Boqueirão granitic pegmatite intruded meta-conglomerates of the Equador Formation during the late Cambrian (502.1 ± 5.8 Ma; ⁴⁰Ar/³⁹Ar plateau age of muscovite). The pegmatite exhibits a typical zonal mineral pattern with four defined zones (Zone I: muscovite, tourmaline, albite, and quartz; Zone II: K-feldspar (microcline), quartz, and albite; Zone III: perthite crystals (blocky feldspar zone); Zone IV: massive quartz). Huge individual beryl, spodumene, tantalite, and cassiterite crystals are common as well. Microscopic examinations revealed that melt inclusions were entrapped simultaneously with fluid inclusions, suggesting the magmatic–hydrothermal transition. The magmatic–hydrothermal transition affected the evolution of the pegmatite, segregating volatile compounds (H₂O, CO₂, N₂) and elements that preferentially partition into a fluid phase from the viscous silicate melt. Fluid inclusion studies on microcline and associated quartz combined with microthermometry and Raman spectroscopy gave an insight into the P-T-X characteristics of entrapped fluids. The presence of spodumene without other LiAl(SiO₃)₂ polymorphs and constructed fluid inclusion isochores limited the magmatic–hydrothermal transition at the gem-bearing Boqueirão granitic pegmatite to the temperature range between 300 and 415 °C at a pressure from 1.8 to 3 kbar. Full article

(This article belongs to the Special Issue Mineralogy and Geochemistry of Gems)

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14 pages, 4280 KiB

Open AccessTechnical Note

Recovering Iron from Iron Ore Tailings and Preparing Concrete Composite Admixtures

by Chang Tang, Keqing Li, Wen Ni and Duncheng Fan

Minerals 2019, 9(4), 232; https://doi.org/10.3390/min9040232 - 15 Apr 2019

Cited by 55 | Viewed by 14546

Abstract

Iron ore tailings (IOTs) are a form of solid waste produced during the beneficiation process of iron ore concentrate. In this paper, iron recovery from IOTs was studied at different points during a process involving pre-concentration followed by direct reduction and magnetic separation. [...] Read more.

Iron ore tailings (IOTs) are a form of solid waste produced during the beneficiation process of iron ore concentrate. In this paper, iron recovery from IOTs was studied at different points during a process involving pre-concentration followed by direct reduction and magnetic separation. Then, slag-tailing concrete composite admixtures were prepared from high-silica residues. Based on the analyses of the chemical composition and crystalline phases, a pre-concentration test was developed, and a pre-concentrated concentrate (PC) with an iron grade of 36.58 wt % and a total iron recovery of 83.86 wt % was obtained from a feed iron grade of 12.61 wt %. Furthermore, the influences of various parameters on iron recovery from PC through direct reduction and magnetic separation were investigated. The optimal parameters were found to be as follows: A roasting temperature of 1250 °C, a roasting time of 50 min, and a 17.5:7.5:12.5:100 ratio of bitumite/sodium carbonate/lime/PC. Under these conditions, the iron grade of the reduced iron powder was 92.30 wt %, and the iron recovery rate was 93.96 wt %. With respect to the original IOTs, the iron recovery was 78.79 wt %. Then, highly active slag-tailing concrete composite admixtures were prepared using the high-silica residues and S75 blast furnace slag powder. When the amount of high-silica residues replacing slag was 20%, the strength of cement mortar blocks at 7 days and 28 days was 33.11 MPa and 50 MPa, respectively, whereas the activity indices were 89 and 108, respectively. Meanwhile, the fluidity rate was appropriately 109. When the content of high-silica residues replacing slag was not more than 30%, the quality of mineral admixtures was not reduced. Last but not least, reusing the high-silica residues during iron recovery enabled the complete utilization of the IOTs. Full article

(This article belongs to the Special Issue Towards a Sustainable Management of Mine Wastes: Reprocessing, Reuse, Revalorization and Repository)

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18 pages, 5093 KiB

Open AccessArticle

The Effect of the Ionic Strength of Process Water on the Interaction of Talc and CMC: Implications of Recirculated Water on Floatable Gangue Depression

by Malibongwe Manono, Kirsten Corin and Jenny Wiese

Minerals 2019, 9(4), 231; https://doi.org/10.3390/min9040231 - 15 Apr 2019

Cited by 11 | Viewed by 4094

Abstract

Previous studies speculate that hydroxo species present in flotation pulps at pH > 9, particularly those of polyvalent cations, selectively adsorb onto gangue minerals. Such species supposedly enhance the depressive action of carboxymethyl cellulose (CMC) onto gangue via an acid-base interaction between the [...] Read more.

Previous studies speculate that hydroxo species present in flotation pulps at pH > 9, particularly those of polyvalent cations, selectively adsorb onto gangue minerals. Such species supposedly enhance the depressive action of carboxymethyl cellulose (CMC) onto gangue via an acid-base interaction between the positively charged mineral surface and the negatively charged CMC molecule. Thus, the hydrophilicity of gangue minerals is enhanced, preventing the dilution of the concentrate. However, as there is little evidence to support these claims for complex process waters of increasing ionic strength, it is important to investigate. Adsorption data and mineral surface charge analyses provide a fundamental understanding of how electrolytes and their ionic strengths affect gangue mineral-depressant adsorption. It is strongly anticipated that decoupling these effects will allow process operators to tailor their process water quality needs towards best flotation operating regimes and, in the long run, effect closed water circuits. Thus, using talc as a proxy for naturally floatable gangue common in sulfidic Cu–Ni–PGM ores, this work investigates the influence of the ionic strength of process water on the adsorption of CMC onto talc for a perspective on how saline water in sulfidic ores would affect the behavior and therefore management of floatable gangue. In the presence of CMC, the microflotation results showed that the rate of talc recovery decreased with increasing ionic strength of process water. Increases in ionic strength resulted in an increase in the adsorption of CMC onto talc. Talc particles proved to have been more coagulated at higher ionic strength since the settling time decreased with increasing ionic strength. Furthermore, the zeta potential of talc particles became less negative at higher ionic strengths of process water. It is thus proposed that increases in the ionic strength of process water increased the zeta potential of talc particles, enhancing the adsorption of CMC onto talc. This in turn created a more coagulated nature on talc particles, increasing their hydrophilicity and thereby retarding floatability. Full article

(This article belongs to the Special Issue Surfactants at Interfaces and Thin Liquid Films)

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12 pages, 3680 KiB

Open AccessArticle

Two Hydrothermal Events at the Shuiyindong Carlin-Type Gold Deposit in Southwestern China: Insight from Sm–Nd Dating of Fluorite and Calcite

by Qinping Tan, Yong Xia, Zhuojun Xie, Zepeng Wang, Dongtian Wei, Yimeng Zhao, Jun Yan and Songtao Li

Minerals 2019, 9(4), 230; https://doi.org/10.3390/min9040230 - 12 Apr 2019

Cited by 23 | Viewed by 3977

Abstract

The Shuiyindong Gold Mine hosts one of the largest and highest-grade, strata-bound Carlin-type gold deposits discovered to date in Southwestern China. The outcrop stratigraphy and drill core data of the deposit reveal Middle–Upper Permian and Lower Triassic formations. The ore is mainly hosted [...] Read more.

The Shuiyindong Gold Mine hosts one of the largest and highest-grade, strata-bound Carlin-type gold deposits discovered to date in Southwestern China. The outcrop stratigraphy and drill core data of the deposit reveal Middle–Upper Permian and Lower Triassic formations. The ore is mainly hosted in Upper Permian bioclastic limestone near the axis of an anticline. The gold is mainly hosted in arsenian pyrite and arsenopyrite, mainly existing in the form of crystal lattice gold, submicroscopic particles and nanoparticles. Fluorite commonly occurs at the vicinity of an unconformity between the Middle–Upper Permian formations, which is proposed to be the structural conduit that fed the ore fluids. Calcite commonly fills fractures at the periphery of decarbonated rocks, which contain high grade orebodies. This study aimed to verify the occurrence of two distinct hydrothermal events at the Shuiyindong, based on Sm–Nd isotope dating of the fluorite and calcite. For this purpose, rare-earth element (REE) concentrations, Sm/Nd isotope ratios, and Sm–Nd isochron ages of the fluorite and calcite were determined. The fluorite and calcite contain relatively high total concentrations of REE (12.3–25.6 μg/g and 5.71–31.7 μg/g, respectively), exhibit variable Sm/Nd ratios (0.52–1.03 and 0.57–1.71, respectively), and yield Sm–Nd isochron ages of 200.1 ± 8.6 Ma and 150.2 ± 2.2 Ma, with slightly different initial

ε_{Nd} (t)

values of −4.4 and −1.1, respectively. These two groups of Sm–Nd isochron ages suggest two episodes of hydrothermal events at the Shuiyindong gold deposit. The age of the calcite probably represents the late stage of the gold mineralization period. The initial

ε_{Nd} (t)

values of the fluorite and calcite indicate that the Nd was probably derived from mixtures of basaltic volcanic tuff and bioclastic limestone from the Permian formations. Full article

(This article belongs to the Special Issue Nanomineralogy)

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17 pages, 8118 KiB

Open AccessArticle

Orebody Modeling from Non-Parallel Cross Sections with Geometry Constraints

by De-Yun Zhong, Li-Guan Wang, Ming-Tao Jia, Lin Bi and Ju Zhang

Minerals 2019, 9(4), 229; https://doi.org/10.3390/min9040229 - 12 Apr 2019

Cited by 10 | Viewed by 3137

Abstract

In this paper, we present an improved approach to the surface reconstruction of orebody from sets of interpreted cross sections that allows for shape control with geometry constraints. The soft and hard constraint rules based on adaptive sampling are proposed. As only the [...] Read more.

In this paper, we present an improved approach to the surface reconstruction of orebody from sets of interpreted cross sections that allows for shape control with geometry constraints. The soft and hard constraint rules based on adaptive sampling are proposed. As only the internal and external position relations of sections are calculated, it is unnecessary to estimate the normal directions of sections. Our key contribution is proposing an iterative closest point correction algorithm. It can be used for iterative correction of the distance field based on the constraint rules and the internal and external position relations of the model. We develop a rich variety of geometry constraints to dynamically control the shape trend of orebody for structural geologists. As both of the processes of interpolation and iso-surface extraction are improved, the performance of this method is excellent. Combined with the interactive tools of constraint rules, our approach is shown to be effective on non-trivial sparse sections. We show the reconstruction results with real geological datasets and compare the method with the existing reconstruction methods. Full article

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19 pages, 1167 KiB

Open AccessArticle

Heat-Assisted Batch Settling of Mineral Suspensions in Inclined Containers

by Cristian Reyes, Christian F. Ihle, Fernando Apaz and Luis A. Cisternas

Minerals 2019, 9(4), 228; https://doi.org/10.3390/min9040228 - 12 Apr 2019

Cited by 7 | Viewed by 3503

Abstract

In mineral processing, the common requirement for progressively finer milling due to the decreasing of ore grades implies the need for more challenging water recovery conditions in thickeners. Several mining operations exist in arid areas, where water recovery becomes critical. The present paper [...] Read more.

In mineral processing, the common requirement for progressively finer milling due to the decreasing of ore grades implies the need for more challenging water recovery conditions in thickeners. Several mining operations exist in arid areas, where water recovery becomes critical. The present paper explores the process of particle separation in batch inclined settlers where the downward facing wall is subject to heating. To this purpose, two-dimensional numerical simulations using a mixture model have been run for a number of combinations of temperature jumps at the downward facing fall, particle diameters, and concentrations. Results show that, for particle sizes on the order of 10 µm, heating has a significant effect on the particle settling velocity at the bottom, but it also promotes particle resuspension, affecting the particle concentration at the supernatant layer. The initial concentration also affects settling: for the concentration range tested (8%–15% by volume), when re-normalized by the average concentration, particle accumulation rates at the bottom were found to be lower for higher average concentrations, thus suggesting that the separation process is more efficient at lower concentrations. Full article

(This article belongs to the Special Issue Modeling, Design and Optimization of Multiphase Systems in Minerals Processing)

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12 pages, 6476 KiB

Open AccessArticle

Germanium Crystal Chemistry in Cu-Bearing Sulfides from Micro-XRF Mapping and Micro-XANES Spectroscopy

by Rémi Belissont, Manuel Munoz, Marie-Christine Boiron, Béatrice Luais and Olivier Mathon

Minerals 2019, 9(4), 227; https://doi.org/10.3390/min9040227 - 12 Apr 2019

Cited by 18 | Viewed by 5493

Abstract

Germanium is considered a critical element, with a demand that has sharply increased due to booming high-technology industries. To understand Ge incorporation mechanisms in natural systems, we investigate Ge speciation in Cu-bearing sulfide minerals using synchrotron X-ray fluorescence (XRF) chemical mapping and Ge [...] Read more.

Germanium is considered a critical element, with a demand that has sharply increased due to booming high-technology industries. To understand Ge incorporation mechanisms in natural systems, we investigate Ge speciation in Cu-bearing sulfide minerals using synchrotron X-ray fluorescence (XRF) chemical mapping and Ge K-edge µ-X-ray absorption near-edge structures (µ-XANES) spectroscopy. The samples investigated include (i) a homogeneous chalcopyrite from the Kipushi polymetallic deposit (Central African copperbelt, D.R. Congo) and (ii) a zoned Ge-rich chalcopyrite from the Barrigão Cu deposit (Iberian pyrite belt, Portugal). First, our spectroscopic analysis supports the occurrence of tetrahedrally-coordinated Ge⁴⁺ in chalcopyrite, independently from origins or zoning patterns observed for these minerals. Then, based on statistical analyses of XRF chemical maps, we demonstrate that tetravalent germanium most likely incorporates chalcopyrite through the Fe crystallographic site via coupled substitutions with the following form: (2x + 3y)Fe³⁺ ⟷ (x + 2y)(Ge,Sn)⁴⁺ + x(Zn,Pb)²⁺ + y(Cu,Ag)⁺, although the presence of lattice vacancies cannot be completely excluded. Full article

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22 pages, 8555 KiB

Open AccessArticle

Coprecipitation of Co²⁺, Ni²⁺ and Zn²⁺ with Mn(III/IV) Oxides Formed in Metal-Rich Mine Waters

by Javier Sánchez-España and Iñaki Yusta

Minerals 2019, 9(4), 226; https://doi.org/10.3390/min9040226 - 10 Apr 2019

Cited by 19 | Viewed by 4386

Abstract

Manganese oxides are widespread in soils and natural waters, and their capacity to adsorb different trace metals such as Co, Ni, or Zn is well known. In this study, we aimed to compare the extent of trace metal coprecipitation in different Mn oxides [...] Read more.

Manganese oxides are widespread in soils and natural waters, and their capacity to adsorb different trace metals such as Co, Ni, or Zn is well known. In this study, we aimed to compare the extent of trace metal coprecipitation in different Mn oxides formed during Mn(II) oxidation in highly concentrated, metal-rich mine waters. For this purpose, mine water samples collected from the deepest part of several acidic pit lakes in Spain (pH 2.7–4.2), with very high concentration of manganese (358–892 mg/L Mn) and trace metals (e.g., 795–10,394 µg/L Ni, 678–11,081 µg/L Co, 259–624 mg/L Zn), were neutralized to pH 8.0 in the laboratory and later used for Mn(II) oxidation experiments. These waters were subsequently allowed to oxidize at room temperature and pH = 8.5–9.0 over several weeks until Mn(II) was totally oxidized and a dense layer of manganese precipitates had been formed. These solids were characterized by different techniques for investigating the mineral phases formed and the amount of coprecipitated trace metals. All Mn oxides were fine-grained and poorly crystalline. Evidence from X-Ray Diffraction (XRD) and Scanning Electron Microscopy coupled to Energy Dispersive X-Ray Spectroscopy (SEM–EDX) suggests the formation of different manganese oxides with varying oxidation state ranging from Mn(III) (e.g., manganite) and Mn(III/IV) (e.g., birnessite, todorokite) to Mn(IV) (e.g., asbolane). Whole-precipitate analyses by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), and/or Atomic Absorption Spectrometry (AAS), provided important concentrations of trace metals in birnessite (e.g., up to 1424 ppm Co, 814 ppm Ni, and 2713 ppm Zn), while Co and Ni concentrations at weight percent units were detected in asbolane by SEM-EDX. This trace metal retention capacity is lower than that observed in natural Mn oxides (e.g., birnessite) formed in the water column in a circum-neutral pit lake (pH 7.0–8.0), or in desautelsite obtained in previous neutralization experiments (pH 9.0–10.0). However, given the very high amount of Mn sorbent material formed in the solutions (2.8–4.6 g/L Mn oxide), the formation of these Mn(III/IV) oxides invariably led to the virtually total removal of Co, Ni, and Zn from the aqueous phase. We evaluate these data in the context of mine water pollution treatment and recovery of critical metals. Full article

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

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16 pages, 1855 KiB

Open AccessArticle

Effect of Depressants and Temperature on Bastnaesite and Monazite Flotation Separation from a Canadian Rare Earth Element (REE) Ore

by Jean-Francois Boulanger, Claude Bazin and Keven Turgeon

Minerals 2019, 9(4), 225; https://doi.org/10.3390/min9040225 - 10 Apr 2019

Cited by 8 | Viewed by 4652

Abstract

A full factorial experimental design was conducted to investigate the effect of temperature and depressants on the flotation of monazite and bastnaesite from carbonate gangue minerals. Temperature, sodium silicate, and guar gum dosage were examined. Mineral reconstruction from energy-dispersive x-ray fluorescence (EDXRF) data [...] Read more.

A full factorial experimental design was conducted to investigate the effect of temperature and depressants on the flotation of monazite and bastnaesite from carbonate gangue minerals. Temperature, sodium silicate, and guar gum dosage were examined. Mineral reconstruction from energy-dispersive x-ray fluorescence (EDXRF) data was performed to quantify bastnaesite, monazite, and gangue mineral recoveries. Bastnaesite and monazite both follow first-order rates of recovery, with bastnaesite recovering faster and to a larger extent than monazite. The main gangue minerals were depressed together. Optimal separation efficiency was achieved using a larger Na₂SiO₃ dosage (2400 g/t), no guar gum addition, and a high temperature (75 °C). The rate of bastnaesite recovery increased with the temperature, while sodium silicate improved the ultimate recovery. An economic analysis was performed to evaluate the impact of increasing Rare Earth Element (REE) recovery by allowing a lower grade concentrate to be generated. Despite the high value of REEs, increasing recovery by producing a concentrate bearing more than 68 wt % carbonaceous gangue was uneconomical. Full article

(This article belongs to the Special Issue Flotation Reagents)

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Minerals, Volume 9, Issue 4 (April 2019) – 55 articles

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