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Volume 10
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Minerals, Volume 10, Issue 12 (December 2020) – 103 articles

Cover Story (view full-size image): This paper sheds light on the production of Egyptian blue, an artificial material widely used as a pigment in the ancient Mediterranean world, based on the examination of pellets from the late Hellenistic workshop of the island of Kos (Greece). Eighteen samples were obtained from pellets of various textures and tones of blue and examined via optical microscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and micro-Raman spectroscopy, providing insight into the composition of the material on the level of the single grain. The results shed light on the firing procedure and possible sources for raw materials. Two process to produce light blue pigments was identified, illustrating the highly specialized knowledge of the ancient craftspeople. View this paper
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15 pages, 10117 KiB  
Article
Lanthanum Role in the Graphite Formation in Gray Cast Irons
by Eduard Stefan, Iulian Riposan, Mihai Chisamera and Stelian Stan
Minerals 2020, 10(12), 1146; https://doi.org/10.3390/min10121146 - 21 Dec 2020
Cited by 3 | Viewed by 2692
Abstract
The present paper reviews original data obtained by the authors from recent separate publications with additional unpublished data, specifically concerning the Lanthanum (La)’s role in the solidification pattern and graphite formation in gray cast irons. Iron melting at 0.018–0.056%S, a 3.7–4.1% carbon equivalent [...] Read more.
The present paper reviews original data obtained by the authors from recent separate publications with additional unpublished data, specifically concerning the Lanthanum (La)’s role in the solidification pattern and graphite formation in gray cast irons. Iron melting at 0.018–0.056%S, a 3.7–4.1% carbon equivalent (CE) and less than 0.005%Alresidual are inoculated with La-bearing FeSi alloys at different associations with other inoculating elements. Complex Al-La small inclusions as possible better nucleation sites for (Mn,X)S compounds and La-Ca presence in the body of these sulfides, which possibly provide better nucleation sites for flake graphite, are identified in 0.026%S cast iron. At a lower sulfur content (0.018%S), La,Ca,Al-FeSi alloy still has a high efficiency, but more complex La-bearing alloys are recommended for a higher dendritic austenite amount (LaBaZrTi–FeSi) or for lower eutectic recalescence (LaBaZr–FeSi). La has limited but specific benefits at 0.05–0.06%S irons, including favorable graphitizing factors (a higher amount of graphite precipitated at the end of solidification), lower eutectic recalescence, and a lower value of the first derivative at the end of solidification. When La,Ca,Ba,Al,Zr,S-FeSi treatment (0.035%S base iron) is used, Scanning Electron Microscopy (SEM) analysis finds that the first formed micro-compound is a complex Al-silicate (Zr,La,Ca,Ba presence), which supports the nucleation of the second compound (Mn,Ca,La)S type. At the sulfide-graphite interface, there is a visible thin (nano size) Al-silicate layer (O-Al-Si-Ca-La system), which is more favorable for graphite nucleation (it has better crystallographic compatibility). La is identified in all three important areas of nucleants (the first is formed oxidic nucleus, the second is nucleated Mn-sulfide and the third is a sulfide-graphite interface), thereby increasing the efficiency of graphite nucleation sites. Full article
(This article belongs to the Special Issue Crystallization and Growth of Graphite)
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14 pages, 1325 KiB  
Article
Reducing the Negative Technogenic Impact of the Mining Enterprise on the Environment through Management of the Water Balance
by Elena Menshikova, Viacheslav Fetisov, Tatyana Karavaeva, Sergey Blinov, Pavel Belkin and Sergey Vaganov
Minerals 2020, 10(12), 1145; https://doi.org/10.3390/min10121145 - 21 Dec 2020
Cited by 7 | Viewed by 2997
Abstract
In terms of anthropogenic impact of mining and processing enterprises, the adjacent territories are contaminated by upstream tailings dams. The contamination is developed by active seepage of liquid waste through the body of the dams. The authors have analyzed water balance at the [...] Read more.
In terms of anthropogenic impact of mining and processing enterprises, the adjacent territories are contaminated by upstream tailings dams. The contamination is developed by active seepage of liquid waste through the body of the dams. The authors have analyzed water balance at the Kachkanar Mining and Processing Plant tailings dump (Russia, Ural Region). The company develops vanadium-containing titanium-magnetite iron ores with low ore (15%). This, along with high productivity, has determined the formation of a large number of tailings and significant amount of wastewater. The purpose of the studies is to substantiate the need to manage the seepage discharge process by means of enclosing dams to ensure environmentally safe operation of the tailings dump. The research objectives included field measurements of seepage volumes, their evaluation by computational methods and analysis of anthropogenic geochemical load on natural waters. The obtained results show an increase in seepage discharge volume from 41.91 million m3 (in 2017) to 81.44 million m3 (in 2026) as the height of the dams increases. These losses will lead to water shortages in the enterprise’s water recycling system. Calculation of pollutants in wastewater with the exception of natural component showed the leading role of technogenic factor in the content of Ti (up to 84%), V (up to 96%), Co (up to 86%) and Mo (up to 93%). Increasing the volume of seepage discharge will lead to an increase in natural water pollution within the area. Ecologically efficient management of the enterprise’s water balance is ensured by the use of tailings thickening technology and implementation of closed water supply systems. Full article
(This article belongs to the Special Issue Elemental Concentration and Pollution in Soil, Water, and Sediment)
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17 pages, 5269 KiB  
Article
Optimization of the Mix Formulation of Geopolymer Using Nickel-Laterite Mine Waste and Coal Fly Ash
by Alberto Longos, Jr., April Anne Tigue, Ithan Jessemar Dollente, Roy Alvin Malenab, Ivyleen Bernardo-Arugay, Hirofumi Hinode, Winarto Kurniawan and Michael Angelo Promentilla
Minerals 2020, 10(12), 1144; https://doi.org/10.3390/min10121144 - 21 Dec 2020
Cited by 25 | Viewed by 4921
Abstract
Geopolymer cement has been popularly studied nowadays compared to ordinary Portland cement because it demonstrated superior environmental advantages due to its lower carbon emissions and waste material utilization. This paper focuses on the formulation of geopolymer cement from nickel–laterite mine waste (NMW) and [...] Read more.
Geopolymer cement has been popularly studied nowadays compared to ordinary Portland cement because it demonstrated superior environmental advantages due to its lower carbon emissions and waste material utilization. This paper focuses on the formulation of geopolymer cement from nickel–laterite mine waste (NMW) and coal fly ash (CFA) as geopolymer precursors, and sodium hydroxide (SH), and sodium silicate (SS) as alkali activators. Different mix formulations of raw materials are prepared to produce a geopolymer based on an I-optimal design and obtained different compressive strengths. A mixed formulation of 50% NMW and 50% CFA, SH-to-SS ratio of 0.5, and an activator-to-precursor ratio of 0.429 yielded the highest 28 d unconfined compressive strength (UCS) of 22.10 ± 5.40 MPa. Furthermore, using an optimized formulation of 50.12% NMW, SH-to-SS ratio of 0.516, and an activator-to-precursor ratio of 0.428, a UCS value of 36.30 ± 3.60 MPa was obtained. The result implies that the synthesized geopolymer material can be potentially used for concrete structures and pavers, pedestrian pavers, light traffic pavers, and plain concrete. 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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16 pages, 10333 KiB  
Article
Origin of Mesozoic Porphyritic Rocks and Regional Magmatic Evolution in the Zijinshan Ore Field of Fujian Province, China: Hf-O Isotope Characteristics of Magmatic Zircons
by Wenhui Zhang, Liyuan Wang, Xupeng Lv, Xiaomin Li, Shuaiqi Yan and Juntao Nie
Minerals 2020, 10(12), 1143; https://doi.org/10.3390/min10121143 - 20 Dec 2020
Viewed by 2234
Abstract
Mesozoic porphyritic rocks from the Zijinshan area, southwestern Fujian Province, China, are andesitic to rhyolitic in composition. The whole-rock SiO2 contents of these rocks are between 62.5% and 78.1%. Magmatic zircon from the Mesozoic porphyritic rocks was determined via secondary-ionization mass spectrometry [...] Read more.
Mesozoic porphyritic rocks from the Zijinshan area, southwestern Fujian Province, China, are andesitic to rhyolitic in composition. The whole-rock SiO2 contents of these rocks are between 62.5% and 78.1%. Magmatic zircon from the Mesozoic porphyritic rocks was determined via secondary-ionization mass spectrometry (SIMS) for the U-Pb age and Hf and O isotopes. The zircon U-Pb ages could be mainly divided into three age groups: Group 1: ~138.8 Ma; Group 2: 109.2~107.4 Ma; and Group 3: 99.7~98.2 Ma. The εHf(t) and δ18O values of the porphyritic zircons showed that the porphyritic rocks in Group 2 were more affected by mantle-derived magma. Combined with previous research results, the medium-acidic magmatism in the southwestern Fujian Province can be divided into eight periods: Paleoproterozoic, Mesoproterozoic, Middle Neoproterozoic, Silurian to Lower Devonian, Permian to Triassic, Middle Jurassic to early Lower Cretaceous, late Lower Cretaceous, and late Lower Cretaceous to early Upper Cretaceous. The Paleoproterozoic crust was the predominant magmatic source for the subsequent Mesoproterozoic to Jurassic magmatism, but the only melts that were closely related to mineralization were derived from partial melting of the Mesoproterozoic crust and a more depleted upper mantle. Full article
(This article belongs to the Special Issue Magma Ascent and Evolution: Insights from Petrology and Geochemistry)
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14 pages, 4352 KiB  
Article
Phase Stability and Vibrational Properties of Iron-Bearing Carbonates at High Pressure
by Chaoshuai Zhao, Liangxu Xu, Weibin Gui and Jin Liu
Minerals 2020, 10(12), 1142; https://doi.org/10.3390/min10121142 - 20 Dec 2020
Cited by 18 | Viewed by 2817
Abstract
The spin transition of iron can greatly affect the stability and various physical properties of iron-bearing carbonates at high pressure. Here, we reported laser Raman measurements on iron-bearing dolomite and siderite at high pressure and room temperature. Raman modes of siderite FeCO3 [...] Read more.
The spin transition of iron can greatly affect the stability and various physical properties of iron-bearing carbonates at high pressure. Here, we reported laser Raman measurements on iron-bearing dolomite and siderite at high pressure and room temperature. Raman modes of siderite FeCO3 were investigated up to 75 GPa in the helium (He) pressure medium and up to 82 GPa in the NaCl pressure medium, respectively. We found that the electronic spin-paring transition of iron in siderite occurred sharply at 42–44 GPa, consistent with that in the neon (Ne) pressure medium in our previous study. This indicated that the improved hydrostaticity from Ne to He had minimal effects on the spin transition pressure. Remarkably, the spin crossover of siderite was broadened to 38–48 GPa in the NaCl pressure medium, due to the large deviatoric stress in the sample chamber. In addition, Raman modes of iron-bearing dolomite Ca1.02Mg0.76Fe0.20Mn0.02(CO3)2 were explored up to 58 GPa by using argon as a pressure medium. The sample underwent phase transitions from dolomite-Ⅰ to -Ⅰb phase at ~8 GPa, and then to -Ⅱ at ~15 and -Ⅲb phase at 36 GPa, while no spin transition was observed in iron-bearing dolomite up to 58 GPa. The incorporation of FeCO3 by 20 mol% appeared to marginally decrease the onset pressures of the three phase transitions aforementioned for pure dolomite. At 55–58 GPa, the ν1 mode shifted to a lower frequency at ~1186 cm−1, which was likely associated with the 3 + 1 coordination in dolomite-Ⅲb. These results shed new insights into the nature of iron-bearing carbonates at high pressure. Full article
(This article belongs to the Special Issue Fe-Bearing Carbonates in the Deep Earth)
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22 pages, 10437 KiB  
Article
The Influence of Hydrothermal Fluids on the REY-Rich Deep-Sea Sediments in the Yupanqui Basin, Eastern South Pacific Ocean: Constraints from Bulk Sediment Geochemistry and Mineralogical Characteristics
by Tiancheng Zhou, Xuefa Shi, Mu Huang, Miao Yu, Dongjie Bi, Xiangwen Ren, Gang Yang and Aimei Zhu
Minerals 2020, 10(12), 1141; https://doi.org/10.3390/min10121141 - 19 Dec 2020
Cited by 40 | Viewed by 4005
Abstract
Rare earth elements (REEs) and yttrium (Y), together known as REY, are extremely enriched in deep-sea pelagic sediments, attracting much attention as a promising new REY resource. To understand the influence of hydrothermal processes on the enrichment of REY in deep-sea sediments from [...] Read more.
Rare earth elements (REEs) and yttrium (Y), together known as REY, are extremely enriched in deep-sea pelagic sediments, attracting much attention as a promising new REY resource. To understand the influence of hydrothermal processes on the enrichment of REY in deep-sea sediments from the eastern South Pacific Ocean, we conducted detailed lithological, bulk sediment geochemical, and in situ mineral geochemical analyses on gravity core sample S021GC17 from the Yupanqui Basin of eastern South Pacific. The REY-rich muds of S021GC17 are dark-brown to black zeolitic clays with REY contents (ΣREY) ranging from 1057 to 1882 ppm (average 1329 ppm). The REY-rich muds display heavy rare earth elements (HREE) enriched patterns, with obvious depletions in Ce, and positive anomalies of Eu in Post-Archean Australian Shale (PAAS)-normalized REE diagrams. In contrast, the muds of S021GC17 show light rare earth elements (LREE) enriched patterns and positive anomalies of Ce and Eu in the seawater-normalized REE diagrams. Total REY abundances in the core show positive correlations with CaO, P2O5, Fe2O3, and MnO concentrations. In situ analyses of trace element contents by laser ablation-inductively coupled plasma–mass spectrometry (LA-ICP-MS) demonstrate that bioapatite fossils contain high REY concentrations (998 to 22,497 ppm, average 9123 ppm), indicating that they are the primary carriers of REY. The in situ Nd isotope values of bioapatites are higher than the average values of seawater in Pacific Ocean. Fe–Mn micronodules are divided into hydrogenetic and diagenetic types, which have average REY concentrations of 1586 and 567 ppm, respectively. The high contents of Fe-Mn-Ba-Co-Mo, the positive correlations between ΣREY and Fe-Mn, the ratios of Fe/Ti and Al/(Al + Fe + Mn), and the LREE-enriched patterns in the REY-rich muds, combined with high Nd isotope values shown by bioapatite fossils, strongly indicate that the hydrothermal fluids have played an important role in the formation of the REY-rich sediments in the eastern South Pacific Ocean. Full article
(This article belongs to the Special Issue Critical Metals in Hydrothermal Ores: Resources, Recovery, and Challenges)
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17 pages, 2341 KiB  
Article
Quality of Peri-Urban Soil Developed from Ore-Bearing Carbonates: Heavy Metal Levels and Source Apportionment Assessed Using Pollution Indices
by Katarzyna Sutkowska, Leslaw Teper, Tomasz Czech, Tomasz Hulok, Michał Olszak and Jan Zogala
Minerals 2020, 10(12), 1140; https://doi.org/10.3390/min10121140 - 19 Dec 2020
Cited by 18 | Viewed by 3777
Abstract
Pollution indices are used to assess the influence of the bedrock as a natural source of heavy-metal (HM), and anthropogenic pollution from ore mining in soils developed from ore-bearing carbonates. The research was conducted in two areas differing in geological setting [...] Read more.
Pollution indices are used to assess the influence of the bedrock as a natural source of heavy-metal (HM), and anthropogenic pollution from ore mining in soils developed from ore-bearing carbonates. The research was conducted in two areas differing in geological setting and type of land use in the Upper Silesia Industrial Region, Southern Poland. Physical properties such as pH, total sulfur, total carbon and total organic carbon values, as well as total Zn, Pb, and Cd contents (ICP-OES) for 39 topsoil samples were measured. Contamination factor (Cf), degree of contamination (Cdeg), pollution load index (PLI) and geoaccumulation index (Igeo), were used to determine the deterioration of topsoil due to HM pollution. The HM content exceeded geochemical background levels by 2.5–18.1 times. Very high to moderate topsoil contamination was determined. In a shallow historical mining zone, the relative influence of particular HM was found to be in the order of Pb > Cd > Zn and, in a deep mining zone, Zn > Cd > Pb. In the topsoil developed over shallow ore bodies, the HM content was mainly (60%) due to naturally occurring HM. In the area of deeply buried ore bodies, 90% of the HM load was related to anthropogenic sources. Zn, Pb and Cd vertical distributions and the patterns of topsoil pollution differ in terms of types of mined ores, mining methods and times elapsed since mining ceased. Pollution indices are an efficient tool for distinguishing soil anthropogenic pollution and geogenic contamination. Full article
(This article belongs to the Special Issue Elemental Concentration and Pollution in Soil, Water, and Sediment)
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32 pages, 12230 KiB  
Article
A Robust Stochastic Approach to Mineral Hyperspectral Analysis for Geometallurgy
by Álvaro F. Egaña, Felipe A. Santibáñez-Leal, Christian Vidal, Gonzalo Díaz, Sergio Liberman and Alejandro Ehrenfeld
Minerals 2020, 10(12), 1139; https://doi.org/10.3390/min10121139 - 18 Dec 2020
Cited by 7 | Viewed by 3826
Abstract
Most mining companies have registered important amounts of drill core composite spectra using different acquisition equipment and by following diverse protocols. These companies have used classic spectrography based on the detection of absorption features to perform semi-quantitative mineralogy. This methodology requires ideal laboratory [...] Read more.
Most mining companies have registered important amounts of drill core composite spectra using different acquisition equipment and by following diverse protocols. These companies have used classic spectrography based on the detection of absorption features to perform semi-quantitative mineralogy. This methodology requires ideal laboratory conditions in order to obtain normalized spectra to compare. However, the inherent variability of spectral features—due to environmental conditions and geological context, among others—is unavoidable and needs to be managed. This work presents a novel methodology for geometallurgical sample characterization consisting of a heterogeneous, multi-pixel processing pipeline which addresses the effects of ambient conditions and geological context variability to estimate critical geological and geometallurgical variables. It relies on the assumptions that the acquisition of hyperspectral images is an inherently stochastic process and that ore sample information is deployed in the whole spectrum. The proposed framework is basically composed of: (a) a new hyperspectral image segmentation algorithm, (b) a preserving-information dimensionality reduction scheme and (c) a stochastic hierarchical regression model. A set of experiments considering white reference spectral characterization and geometallurgical variable estimation is presented to show promising results for the proposed approach. Full article
(This article belongs to the Special Issue Advanced Spectral Techniques for Mineralogical and Elemental Analysis in Mining and Mineral Processing)
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18 pages, 5302 KiB  
Article
Hyperspectral Characteristics of Oil Sand, Part 1: Prediction of Processability and Froth Quality from Measurements of Ore
by Benoit Rivard, Jilu Feng, Derek Russell, Vivek Bhushan and Michael Lipsett
Minerals 2020, 10(12), 1138; https://doi.org/10.3390/min10121138 - 18 Dec 2020
Cited by 2 | Viewed by 2306
Abstract
This study is the first of two companion papers using hyperspectral data to generate predictive models of oil sand ore and froth characteristics as a potential new means for process control. In Alberta, Canada, shallow oil sands deposits are accessed by surface mining [...] Read more.
This study is the first of two companion papers using hyperspectral data to generate predictive models of oil sand ore and froth characteristics as a potential new means for process control. In Alberta, Canada, shallow oil sands deposits are accessed by surface mining and crushed ore is transported to a processing plant for extraction of bitumen using flotation processes. The ore displays considerable variability in clay, bitumen, and fines which affects their behavior in flotation units. Using oil sand ore spanning a range of bitumen and fines characteristics, flotation experiments were performed to generate froth in a batch extractor to determine ore processability (e.g., separation performance) and froth characteristics (color, bitumen, solids). From hyperspectral observations of ore, models can predict the %bitumen content and %fines (particle passing at 44 and 3.9 µm) of ore but the models with highest r2 (>0.96) predict the solids/bitumen of froth and the processability of ore. Spectral observations collected on ore upstream of the separation vessels could therefore offer a first order assessment of froth quality for an ore blend before the ore enters the plant. These models could also potentially be used to monitor and control the performance of the blending process as another means to control the performance of the flotation process. Full article
(This article belongs to the Special Issue Mineral-Organic Interactions Related to Oil Sands Processing)
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20 pages, 7361 KiB  
Article
Hyperspectral Characteristics of Oil Sand, Part 2: Prediction of Froth Characteristics from Measurements of Froth
by Benoit Rivard, Jilu Feng, Derek Russell, Vivek Bushan and Michael Lipsett
Minerals 2020, 10(12), 1137; https://doi.org/10.3390/min10121137 - 18 Dec 2020
Cited by 2 | Viewed by 1988
Abstract
This is the second part of a study of predictive models of oil sand ore and froth characteristics using infrared hyperspectral data as a potential new means for process control. In Alberta, Canada, bitumen in shallow oil sands deposits is accessed by surface [...] Read more.
This is the second part of a study of predictive models of oil sand ore and froth characteristics using infrared hyperspectral data as a potential new means for process control. In Alberta, Canada, bitumen in shallow oil sands deposits is accessed by surface mining and then extracted from ore using flotation processes. The ore displays variability in the clay, bitumen, and fines content and this variability affects the separability and product quality in flotation units. Flotation experiments were performed on a set of ore samples of different types to generate froth and determine the ore processability (e.g., separation performance) and froth characteristics (bitumen and solids content, fines distribution). We show that point spectra and spectral imagery of good quality can be acquired rapidly (<1 s and <15 s, respectively) and these capture spectral features diagnostic of bitumen and solids. Ensuing models can predict the solids/bitumen (r2 = 0.88) and the %fines and ultrafines (particle passing at 3.9 and 0.5 µm) content of froth (r2 = 0.8 and 0.9, respectively). The latter model could be used to reject froth with a high solids content. Alternately, the strength of the illite-smectite absorption observed in froth could be used to retain all the samples above a pre-defined processability. Given that point spectrometers can currently be acquired for less than half the cost of an imaging system, we recommend the use of the former for future trials in operating environments. Full article
(This article belongs to the Special Issue Mineral-Organic Interactions Related to Oil Sands Processing)
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30 pages, 6445 KiB  
Article
Geochronological and Geochemical Constraints on the Origin of the Hutouya Polymetallic Skarn Deposit in the East Kunlun Orogenic Belt, NW China
by Hongchang Gao, Fengyue Sun, Bile Li, Ye Qian, Li Wang and Yajing Zhang
Minerals 2020, 10(12), 1136; https://doi.org/10.3390/min10121136 - 18 Dec 2020
Cited by 3 | Viewed by 2459
Abstract
The Hutouya polymetallic skarn deposit lies in the Qimantagh area of the East Kunlun Orogenic Belt, NW China. Skarnization and mineralization at the deposit are closely associated with contemporary felsic intrusions. In this paper, zircon U-Pb ages and zircon Hf isotope as well [...] Read more.
The Hutouya polymetallic skarn deposit lies in the Qimantagh area of the East Kunlun Orogenic Belt, NW China. Skarnization and mineralization at the deposit are closely associated with contemporary felsic intrusions. In this paper, zircon U-Pb ages and zircon Hf isotope as well as whole-rock geochemical and whole-rock Sr-Nd isotope data are reported for intrusive rocks and crystal tuff of the Elashan Formation in the Hutouya area. Moreover, Re-Os ages and S-Pb isotopes are also reported for the ore minerals in the Hutouya deposit. The Zircon laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U-Pb age of granodiorite and Re-Os isochron age of molybdenite suggest that mineralizations occurred at ca. 227 Ma and that the granodiorite and molybdenite are closely related petrogenetically. All the granitoids in the Hutouya deposit are high-K calc-alkaline and metaluminous to weakly peraluminous I-type granitoids. Among them, the ore-forming granitoids were derived by the mixing of crust-derived (either juvenile or ancient mature lower crust) and mantle-derived magmas, whereas the non-ore-related granite porphyry was generated by the partial melting of a single ancient mature lower crust. The magmas of all the granitoids underwent extensive fractionation–crystallization during the process of rising and emplacement. The sulfur of the analyzed samples from the northern and middle zone of Hutouya deposit (including No. II, III, IV, and VI ore belts) belongs to deep magmatic sulfur, while the sulfur of samples from the southern zone of Hutouya deposit (No. VII ore belt) includes not only deep magmatic sulfur but also a contribution of strata sulfur. All the ore mineral samples in the Hutouya deposit have similar Pb compositions that are consistently derived from a mixed source of upper crust and mantle. Tectonic discrimination diagrams indicate a post-collisional setting for all granitic rocks of the Hutouya skarn deposit, which is therefore considered a product of a the post-collision extensional system and is consistent with other porphyry-skarn deposits within the East Kunlun Orogenic Belt. Full article
(This article belongs to the Section Mineral Deposits)
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19 pages, 5095 KiB  
Article
Deeply Buried Authigenic Carbonates in the Qiongdongnan Basin, South China Sea: Implications for Ancient Cold Seep Activities
by Jiangong Wei, Tingting Wu, Wei Zhang, Yinan Deng, Rui Xie, Junxi Feng, Jinqiang Liang, Peixin Lai, Jianhou Zhou and Jun Cao
Minerals 2020, 10(12), 1135; https://doi.org/10.3390/min10121135 - 17 Dec 2020
Cited by 22 | Viewed by 3280
Abstract
Cold seep carbonates are important archives of pore water chemistry and ancient methane seepage activity. They also provide an important contribution to the global carbon sink. Seep carbonates at three sediment layers (3.0, 52.1, and 53.6 mbsf) were collected at site W08B in [...] Read more.
Cold seep carbonates are important archives of pore water chemistry and ancient methane seepage activity. They also provide an important contribution to the global carbon sink. Seep carbonates at three sediment layers (3.0, 52.1, and 53.6 mbsf) were collected at site W08B in the Qiongdongnan Basin of the South China Sea. This study investigated the mineralogy, microstructure, stable carbon and oxygen isotopes, trace elements, and U-Th dates of these carbonates to identify the relationship between methane flux and authigenic carbonate precipitation. The results showed that the δ13C and δ18O values of all carbonates are similar, indicating that the carbon source for shallow carbonates and deep carbonates has remained constant over time and included biogenic and thermogenic methane. Although carbonates were found in three sediment layers, the two main stages of methane seepage events were discernible, which was likely caused by the dissociation of gas hydrates. The first methane seep took place at 131.1–136.3 ka BP. During a dramatic drop in the sea level, the seep carbonate at 52.1 mbsf formed at 136.3 ka BP through the anaerobic oxidation of methane (AOM). The carbonate at 53.6 mbsf resulted from the vertical downward movement of the sulfate-methane transition zone with decreasing methane flux at 131.1 ka BP. This is the reason for the age of carbonates at 52.1 mbsf being older than the age of carbonates at 53.6 mbsf. The second methane seep took place at 12.2 ka BP. Shallow carbonate formed at that time via AOM and is now located at 3 mbsf. Moreover, thin-section photomicrographs of deep carbonate mainly consisted of matrix micrite and biological debris and acicular aragonite occurred as vein cement filling the pore spaces between the matrix micrite. The acicular aragonite was mainly influenced by the timing of the carbonate precipitation of minerals. This research identified a long history of methane seep activity reflected by the vertical distribution of carbonates. Full article
(This article belongs to the Special Issue Trace Elements in Carbonates: Isotopic and Geochronological Record)
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17 pages, 5122 KiB  
Article
Enhancing Ion Flotation through Decoupling the Overflow Gas and Liquid Fluxes
by Siân Baynham, Peter Ireland and Kevin Galvin
Minerals 2020, 10(12), 1134; https://doi.org/10.3390/min10121134 - 17 Dec 2020
Cited by 9 | Viewed by 2795
Abstract
Conventional ion flotation is hydrodynamically constrained by coupling of the gas flux and liquid flux that report to the concentrate. This constraint has greatly limited the industrial application of ion flotation, despite its remarkable effectiveness in extracting ionic species down to very low [...] Read more.
Conventional ion flotation is hydrodynamically constrained by coupling of the gas flux and liquid flux that report to the concentrate. This constraint has greatly limited the industrial application of ion flotation, despite its remarkable effectiveness in extracting ionic species down to very low concentrations, of order 1 ppm. Previous work demonstrated that these hydrodynamic constraints could be significantly relaxed using the reflux flotation cell (RFC), a system incorporating parallel inclined channels to improve bubble-liquid segregation. However, it was found that bubble coalescence placed an additional limit on performance. In this study the impact of coalescence was minimized by reducing the volume reduction from 20 to 5, ensuring sufficient liquid reported to the concentrate with the bubbles. Under these conditions, an equivalent adsorptive recovery was achieved using the RFC at feed fluxes up to four times those in the conventional system. The maximum adsorptive extraction rate achieved with the RFC was three times that for the conventional system. A refined experimental methodology was used to quantify much more accurately the relative hydrodynamic limits of conventional and RFC operation. The previously neglected issue of split-zone segregation, resulting in smaller bubbles in the lower part of the cell, was also investigated. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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12 pages, 4065 KiB  
Article
Transition of Sulphide Self-Heating from Stage A to Stage B
by Sungjae Moon, Frank Rosenblum, Yuehua Tan, Kristian E. Waters and James A. Finch
Minerals 2020, 10(12), 1133; https://doi.org/10.3390/min10121133 - 17 Dec 2020
Cited by 4 | Viewed by 2300
Abstract
Previous work has shown that sulphide self-heating occurs in three distinct stages, referred to as Stage A, Stage B and Stage C. In this publication, the focus is the transition from Stage A to Stage B which occurs at ca. 100 °C. Background [...] Read more.
Previous work has shown that sulphide self-heating occurs in three distinct stages, referred to as Stage A, Stage B and Stage C. In this publication, the focus is the transition from Stage A to Stage B which occurs at ca. 100 °C. Background literature hints that the transition corresponds to the transformation of the rhombic form of elemental sulphur to the more reactive monoclinic form that occurs at 96 °C. A test apparatus is modified for adiabatic heating to track the transition. The results support this transformation of sulphur as being key to the transition, and the transition temperature is thus modified to 96 °C. Variations in a sample’s response under adiabatic conditions are observed and possible reasons are discussed. Testing in adiabatic mode provides new insights into the sulphide self-heating process that complements the test designed to identify propensity to self-heat. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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14 pages, 3761 KiB  
Article
A Column Leaching Model of Low-Grade Chalcopyrite Ore: Mineral Preferences and Chemical Reactivity
by Heike Bostelmann and Gordon Southam
Minerals 2020, 10(12), 1132; https://doi.org/10.3390/min10121132 - 17 Dec 2020
Cited by 1 | Viewed by 2071
Abstract
Bioleaching models to examine copper extraction from low-grade chalcopyrite ores were set up to identify the influence of pyrite on leaching efficacy. A combination of scanning electron microscopy and geochemical analysis showed that extraction was marginally enhanced by the addition of pyrite when [...] Read more.
Bioleaching models to examine copper extraction from low-grade chalcopyrite ores were set up to identify the influence of pyrite on leaching efficacy. A combination of scanning electron microscopy and geochemical analysis showed that extraction was marginally enhanced by the addition of pyrite when using a combination of Leptospirillum ferrooxidans, an iron oxidiser, Acidithiobacillus thiooxidans, a sulphur oxidising species and Acidithiobacillus ferrooxidans, an iron and sulphur oxidiser. Extensive biofilms formed on the pyrite surfaces (>106 cells/mm2) but were severely limited on chalcopyrite, possessing approximately the same number of cells as quartz grains, an internal non-nutrient control “substrate” (with ca. 2 × 103 cells/mm2). The presence of dissolved copper did not inhibit the growth of this consortium. Indirect “bioleaching” of chalcopyrite appears to be limited by proton activity at the chalcopyrite surface. Full article
(This article belongs to the Special Issue Bio-recovery of Copper, Lead and Zinc)
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21 pages, 12066 KiB  
Article
Deciphering the Iron Provenance on a Medieval Building Yard: The Case of Bourges Cathedral
by Maxime L’Héritier, Philippe Dillmann and Guillaume Sarah
Minerals 2020, 10(12), 1131; https://doi.org/10.3390/min10121131 - 16 Dec 2020
Cited by 9 | Viewed by 3262
Abstract
This paper presents the provenance study of the iron reinforcements of Bourges Cathedral (13th c.): the links of a 100 m long iron chain, surrounding the eastern parts of the cathedral at the triforium level and 4.5 to 5 m long tie-rods consolidating [...] Read more.
This paper presents the provenance study of the iron reinforcements of Bourges Cathedral (13th c.): the links of a 100 m long iron chain, surrounding the eastern parts of the cathedral at the triforium level and 4.5 to 5 m long tie-rods consolidating the arches of the inner aisle at the same level. The analytical methodology is based on the determination of trace rare earth elements analyses by LA-ICP-MS in the slag inclusions of the artefacts and in the slag found on candidate production sites combined with statistical approaches. This chemical approach is crossed with archaeological and historical studies on the monument itself and on the production sites. Ninety-nine iron samples were analyzed on the bars and chains and 238 iron slags from 3 presumed areas of supply. For the first time, iron circulation and trade around a single building yard over a time of 30 to 40 years is studied with a precision never obtained before with historical sources. It shows that mainly four different metallurgical districts, local and more distant, supplied the building yard, mostly depending on the construction phases and also on the types of iron armatures needed. Full article
(This article belongs to the Special Issue Mineralogy, Trace Elements and Isotopic Tracers in Archaeometallurgy)
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15 pages, 58986 KiB  
Article
3D Spatial Distribution of Arsenic in an Abandoned Mining Area: A Combined Geophysical and Geochemical Approach
by Jesús Ruiz-Roso, Mari Luz García-Lorenzo, Pedro Castiñeiras, Alfonso Muñoz-Martín and Elena Crespo-Feo
Minerals 2020, 10(12), 1130; https://doi.org/10.3390/min10121130 - 15 Dec 2020
Cited by 2 | Viewed by 2679
Abstract
Abandoned mine wastes, containing high sulfide contents, are of particular concern because of the formation of acid mine drainage (AMD), becoming an active and harmful point source of potentially toxic elements (PTEs) to the environment. A detailed evaluation of the chemical and mineralogical [...] Read more.
Abandoned mine wastes, containing high sulfide contents, are of particular concern because of the formation of acid mine drainage (AMD), becoming an active and harmful point source of potentially toxic elements (PTEs) to the environment. A detailed evaluation of the chemical and mineralogical composition of mining wastes is necessary to determine effective remediation actions. Due to the high amount of generated wastes as a result of mining and processing activities, the cost and time consumed for this characterization are limiting. Hence, efficient tools could be applied to predict the composition of these wastes and their spatial distribution. This study aims to determine the physico-chemical characterization of wastes from mining activities using geochemical and geophysical techniques. The obtained results, both geochemical and geophysical, allow us to locate areas with a high potential risk of contamination by As in an economic and simple way, and enable us to design detailed geochemical sampling campaigns. In addition, the fact that there are conductive fractures in depth suggests the possible circulation of contaminants through them as well as the preferential lines of circulation. Full article
(This article belongs to the Special Issue Environmental Geochemistry of Mineral Deposits)
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15 pages, 2967 KiB  
Article
Experimental Study on the Link between Optical Emission, Crystal Defects and Photocatalytic Activity of Artist Pigments Based on Zinc Oxide
by Alessia Artesani, Maria Vittoria Dozzi, Lucia Toniolo, Gianluca Valentini and Daniela Comelli
Minerals 2020, 10(12), 1129; https://doi.org/10.3390/min10121129 - 15 Dec 2020
Cited by 8 | Viewed by 2396
Abstract
The historical knowledge inherited from house paint documents and the experimental research on synthetic pigments show that production methods have an important role in the performance of paint. In this regard, this work investigates the links existing between the optical emission, crystal defects [...] Read more.
The historical knowledge inherited from house paint documents and the experimental research on synthetic pigments show that production methods have an important role in the performance of paint. In this regard, this work investigates the links existing between the optical emission, crystal defects and photocatalytic activity of zinc white pigment from different contemporary factories, with the aim of elucidating the effects of these characteristics onto the tendency of the pigment to induce paint failures. The analysed samples display highly similar crystallite structure, domain size, and specific surface area, whilst white pigments differ from pure ZnO in regards to the presence of zinc carbonate hydrate that is found as a foreign compound. In contrast, the photoluminescence measurements categorize the analysed samples into two groups, which display different trap-assisted emissions ascribed to point crystal defects introduced during the synthesis process, and associated to Zn or O displacement. The photocatalytic degradation tests infer that the emerged defective structure and specific surface area of ZnO-based samples influence their tendency to oxidize organic molecules under light irradiation. In particular, the results indicate that the zinc interstitial defects may be able to promote the photogenerated electron-hole couples separation with a consequent increase of the overall ZnO photocatalytic activity, negatively affecting the binding medium stability. This groundwork paves the way for further studies on the link between the photoluminescence emission of the zinc white pigment and its tendency to decompose organic components contained in the binding medium. Full article
(This article belongs to the Special Issue Spectral Behavior of Mineral Pigments)
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23 pages, 27379 KiB  
Article
The Paleozoic-Aged University Foidolite-Gabbro Pluton of the Northeastern Part of the Kuznetsk Alatau Ridge, Siberia: Geochemical Characterization, Geochronology, Petrography and Geophysical Indication of Potential High-Grade Nepheline Ore
by Agababa A. Mustafaev, Igor F. Gertner, Richard E. Ernst, Pavel A. Serov and Yurii V. Kolmakov
Minerals 2020, 10(12), 1128; https://doi.org/10.3390/min10121128 - 15 Dec 2020
Cited by 7 | Viewed by 3681
Abstract
Geological, geochemical and ground magnetic techniques are used to characterize the University alkaline-gabbroid pluton and crosscutting N-S trending alkaline dikes, located northeast of the Kuznetsk Alatau ridge, Siberia. Trace element concentrations and isotopic compositions of the igneous units were determined by XRF, ICP-MS [...] Read more.
Geological, geochemical and ground magnetic techniques are used to characterize the University alkaline-gabbroid pluton and crosscutting N-S trending alkaline dikes, located northeast of the Kuznetsk Alatau ridge, Siberia. Trace element concentrations and isotopic compositions of the igneous units were determined by XRF, ICP-MS and isotope analysis. The Sm-Nd age of subalkaline (melanogabbro, leucogabbro 494–491 Ma) intrusive phases and crosscutting alkaline dikes (plagioclase ijolite, analcime syenite 392–389 Ma) suggests two stages of activity, likely representing separate events. The subalkaline and alkaline rocks are characterized by low silicic acidity (SiO2 = 41–49 wt %), wide variations in alkalinity (Na2O + K2O = 3–19 wt %; Na2O/K2O = 1.2–7.2 wt %), high alumina content (Al2O3 = 15–28 wt %) and low titanium content (TiO2 = 0.07–1.59 wt %). The new trace element data for subalkaline rocks (∑REE 69–280 ppm; La/Yb 3.7–10.2) of the University pluton and also the crosscutting younger (390 Ma) alkaline dikes (∑REE 10–1567 ppm; La/Yb 0.7–17.8 ppm) both reflect an intermediate position between oceanic island basalts (OIBs) and island arc basalts (IABs). The presence of a negative Nb–Ta anomaly and the relative enrichment in Rb, Ba, Sr, and U indicate a probable interaction of mantle plume material with the lithospheric mantle beneath previously formed accretion complexes of subduction zones. The isotopic signatures of strontium (εSr(T) +3.13–+28.31) and neodymium (εNd(T) +3.2–+8.7) demonstrate the evolution of parental magmas from a plume source from moderately depleted PREMA mantle, whose derivatives underwent selective crustal contamination. Full article
(This article belongs to the Special Issue Ore Genesis and Metamorphism: Geochemistry, Mineralogy, and Isotopes)
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19 pages, 5146 KiB  
Article
Laboratory Studies of Small Strain Stiffness and Modulus Degradation of Warsaw Mineral Cohesive Soils
by Emil Soból, Katarzyna Gabryś, Karina Zabłocka, Raimondas Šadzevičius, Rytis Skominas and Wojciech Sas
Minerals 2020, 10(12), 1127; https://doi.org/10.3390/min10121127 - 15 Dec 2020
Cited by 11 | Viewed by 3660
Abstract
The shear modulus and normalized shear modulus degradation curve are the fundamental parameters describing soil behavior. Thus, this article is focused on the stiffness characteristic of 15 different Warsaw cohesive soli represented by the parameters mentioned above. In this research, standard resonant column [...] Read more.
The shear modulus and normalized shear modulus degradation curve are the fundamental parameters describing soil behavior. Thus, this article is focused on the stiffness characteristic of 15 different Warsaw cohesive soli represented by the parameters mentioned above. In this research, standard resonant column tests were performed in a wide shear strain range, from a small one, where soil behaves like an elastic medium, to a medium one, where soil has an unrecoverable deformation. Collected data allows the authors to create empirical models describing stiffness characteristics with high reliability. The maximum shear modulus calculated by the proposed equation for Warsaw cohesive soil had a relative error of about 6.8%. The formula for normalized shear modulus estimated G/GMAX with 2.2% relative error. Combined empirical models for GMAX, and G/GMAX allow the evaluation of Warsaw cohesive soil’s shear modulus value in a wide shear deformation range, with a very low value of the relative error of 6.7%. Full article
(This article belongs to the Special Issue Clays, Clay Minerals and Geology)
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19 pages, 7346 KiB  
Article
A Multi-Model Ensemble Approach for Gold Mineral Prospectivity Mapping: A Case Study on the Beishan Region, Western China
by Kaijian Wang, Xinqi Zheng, Gongwen Wang, Dongya Liu and Ning Cui
Minerals 2020, 10(12), 1126; https://doi.org/10.3390/min10121126 - 15 Dec 2020
Cited by 8 | Viewed by 2605
Abstract
Mineral prospectivity mapping (MPM) needs robust predictive techniques so that the target zones of mineral deposits can be accurately delineated at a specific location. Although an individual machine learning algorithm has been successfully applied, it remains a challenge because of the complicated non-linear [...] Read more.
Mineral prospectivity mapping (MPM) needs robust predictive techniques so that the target zones of mineral deposits can be accurately delineated at a specific location. Although an individual machine learning algorithm has been successfully applied, it remains a challenge because of the complicated non-linear relations between prospecting factors and deposits. Ensemble learning methods were efficiently applied for their excellent generalization, but their potential has not been fully explored in MPM. In this study, three well-known machine learning models, namely random forest (RF), support vector machine (SVM), and the maximum entropy model (MaxEnt), were fused into ensembles (i.e., RF–SVM, RF–MaxEnt, SVM–MaxEnt, RF–SVM–MaxEnt) to produce a final prediction. The paper aims to investigate the potential application of stacking ensemble learning methods (SELM) for MPM. In this study, 69 hydrothermal gold deposits were split into two parts: 70% for the training model and 30% for testing the model. Then, 11 mineral prospecting factors were selected as a spatial dataset constructed for MPM. Finally, the models’ performance was assessed using the receiver operating characteristic (ROC) curves and five statistical metrics. Compared with other single methods, the SELM framework showed an improved predictive performance in the model evaluation. Therefore, this finding suggests that the SELM framework is promising and should be selected as an alternative technique for MPM. Full article
(This article belongs to the Special Issue Geological Modelling, Volume II)
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24 pages, 9608 KiB  
Article
Trace Elements in Apatite as Genetic Indicators of the Evate Apatite-Magnetite Deposit, NE Mozambique
by Marek Slobodník, Veronika Dillingerová, Michaela Blažeková, Monika Huraiová and Vratislav Hurai
Minerals 2020, 10(12), 1125; https://doi.org/10.3390/min10121125 - 14 Dec 2020
Cited by 2 | Viewed by 3845
Abstract
The Evate deposit is a Neoproterozoic (~590 Ma) magnetite-apatite-carbonate body emplaced parallel to foliation of the Monapo granulite complex in NE Mozambique. A complicated history of the deposit is recorded in apatite textures visualized in cathodoluminescence (CL) images. In spite of different solid [...] Read more.
The Evate deposit is a Neoproterozoic (~590 Ma) magnetite-apatite-carbonate body emplaced parallel to foliation of the Monapo granulite complex in NE Mozambique. A complicated history of the deposit is recorded in apatite textures visualized in cathodoluminescence (CL) images. In spite of different solid and fluid inclusions, mineral assemblages, and the CL textures, electron probe microanalyses indicate relatively consistent apatite compositions corresponding to fluorapatite (XF = 0.51–0.73, XOH = 0.21–0.47, XCl = 0.02–0.06) with limited belovite- and cesanite-type substitutions. Laser ablation inductively coupled plasma mass spectrometric analyses show that apatites from unaltered magnetite-forsterite-spinel ores are depleted in Y, REE, Ba, and Sr compared to apatites from carbonate-anhydrite ores. Hydrothermally overprinted apatites with complex patchy domain CL textures are enriched in Y-REE in greenish-grey zones, Fe-U-Th in blue zones, and Mn-Sr-Ba in brown domains. Observed CL-emissions in the Evate apatites result from very subtle variations in REE, Mn, and U contents controlled by the variability of redox conditions. The decreased Th:U ratio in the hydrothermally overprinted apatites reflects the oxidation and partial removal of U4+ from the apatite structure during the interaction with oxidizing aqueous fluids capable of transporting U6+. Flat, LREE (La-Sm)-enriched chondrite-normalized patterns with Eu/Eu* = 0.7–1.4 and Ce/Ce* = 0.9–1.5, together with concentrations of diagnostic trace elements (Sr, Mn, Y, REE) are consistent with apatites from magmatic carbonatites and phoscorites. This study corroborates that the Evate deposit is a post-collisional orogenic carbonatite genetically linked with mafic plutonic rocks intruding the Monapo granulite complex after granulite-facies metamorphism, and later overprinted by intensive hydrothermalism. The Evate apatite is peculiar in retaining its pristine magmatic signature despite the extensive hydrothermal-metasomatic alteration accompanied by dissolution-reprecipitation. Full article
(This article belongs to the Special Issue Crystallography and Mineralogy of Phosphates)
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24 pages, 7517 KiB  
Article
Copper-Containing Agates of the Avacha Bay (Eastern Kamchatka, Russia)
by Galina Palyanova, Evgeny Sidorov, Andrey Borovikov and Yurii Seryotkin
Minerals 2020, 10(12), 1124; https://doi.org/10.3390/min10121124 - 14 Dec 2020
Cited by 6 | Viewed by 3114
Abstract
The copper-containing agates of the Avacha Bay (Eastern Kamchatka, Russia) have been investigated in this study. Optical microscopy, scanning electron microscopy, electron microprobe analysis, X-ray powder diffraction, Raman spectroscopy, and fluid inclusions were used to investigate the samples. It was found that copper [...] Read more.
The copper-containing agates of the Avacha Bay (Eastern Kamchatka, Russia) have been investigated in this study. Optical microscopy, scanning electron microscopy, electron microprobe analysis, X-ray powder diffraction, Raman spectroscopy, and fluid inclusions were used to investigate the samples. It was found that copper mineralization in agates is represented by native copper, copper sulphides (chalcocite, djurleite, digenite, anilite, yarrowite, rarely chalcopyrite) and cuprite. In addition to copper minerals, sphalerite and native silver were also found in the agates. Native copper is localized in a siliceous matrix in the form of inclusions usually less than 100 microns in size—rarely up to 1 mm—forming dendrites and crystals of a cubic system. Copper sulphides are found in the interstices of chalcedony often cementing the marginal parts of spherule aggregates of silica. In addition, they fill the micro veins, which occupy a cross-cutting position with respect to the concentric bands of chalcedony. The idiomorphic appearance of native copper crystals and clear boundaries with the silica matrix suggest their simultaneous crystallization. Copper sulphides, cuprite, and barite micro veins indicate a later deposition. Raman spectroscopy and X-ray powder diffraction results demonstrated that the Avacha Bay agates contained cristobalite in addition to quartz and moganite. The fluid inclusions study shows that the crystalline quartz in the center of the nodule in agates was formed with the participation of solutions containing a very low salt concentration (<0.3 wt.% NaCl equivalent) at the temperature range 110–50 °C and below. The main salt components were CaCl2 and NaCl, with a probable admixture of MgCl2. The copper mineralization in the agates of the Avacha Bay established in the volcanic strata can serve as a direct sign of their metallogenic specialization. Full article
(This article belongs to the Special Issue Agates: Types, Mineralogy, Deposits, Host Rocks, Ages and Genesis)
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21 pages, 8523 KiB  
Article
Possibilities and Limitations of the Use of Seafloor Photographs for Estimating Polymetallic Nodule Resources—Case Study from IOM Area, Pacific Ocean
by Monika Wasilewska-Błaszczyk and Jacek Mucha
Minerals 2020, 10(12), 1123; https://doi.org/10.3390/min10121123 - 14 Dec 2020
Cited by 12 | Viewed by 4928
Abstract
Direct seafloor sampling using, e.g., box corers is insufficient to obtain an acceptable accuracy of nodule resource estimates in small parts of potential deposits. In order to increase the reliability of the estimates, it was rational to use the results of photographic surveys [...] Read more.
Direct seafloor sampling using, e.g., box corers is insufficient to obtain an acceptable accuracy of nodule resource estimates in small parts of potential deposits. In order to increase the reliability of the estimates, it was rational to use the results of photographic surveys of the seafloor. However, the estimation of nodule abundance based on seafloor photographs is associated with a number of problems and limitations. The main goal of the study was a statistical analysis of the role and interrelationships of selected factors affecting the accuracy of nodule abundance assessment based on seafloor photographs from the H22 exploration block located in the Interoceanmetal Joint Organization (IOM) area in the Pacific. A statistically significant, but only moderately strong, correlation was found between the abundance of nodules and seafloor nodule coverage (quantitative variables), the nodule abundance and genetic type of nodules (ordinal variable estimated visually from photos), and between seafloor coverage with nodules and sediment coverage of nodules (ordinal variable estimated visually from photos). It was suggested that the nodule abundance could be effectively and more accurately predicted using a general linear model that includes both quantitative and ordinal variables. Full article
(This article belongs to the Special Issue Exploration of Polymetallic Nodules)
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13 pages, 1874 KiB  
Article
Quantitative Evaluation of Crystalline and Amorphous Phases in Clay-Based Cordierite Ceramic
by Zdeněk Klika, Marta Valášková, Lucie Bartoňová and Petra Maierová
Minerals 2020, 10(12), 1122; https://doi.org/10.3390/min10121122 - 14 Dec 2020
Cited by 9 | Viewed by 3080
Abstract
An innovative chemical quantitative mineral analysis (CQMA) was successfully tested on a cordierite-based clay ceramic sample to quantify crystalline and amorphous components. The accuracy of this method was demonstrated on an added module to the CQMA program that used oxide formulas of amorphous [...] Read more.
An innovative chemical quantitative mineral analysis (CQMA) was successfully tested on a cordierite-based clay ceramic sample to quantify crystalline and amorphous components. The accuracy of this method was demonstrated on an added module to the CQMA program that used oxide formulas of amorphous phases obtained by energy dispersive X-ray spectroscopy (EDS) microprobe chemical analysis. This CQMA method was tested for three variants calculated using chemical analysis, i.e., X-ray diffraction (XRD) identification of crystalline (cordierite and enstatite) and amorphous phases by scanning electron microscopy (SEM)/EDS texture and microanalyses. The test results from CQMA suggest their application possibilities as well as the limits of their utilization. Full article
(This article belongs to the Special Issue Clay Minerals and Waste Fly Ash Ceramics)
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16 pages, 2657 KiB  
Article
Sorption of Cu2+ Ions by Bentonite Modified with Al Keggin Cations and Humic Acid in Solutions with pH 4.5
by Yulia Izosimova, Inna Tolpeshta, Irina Gurova, Michail Karpukhin, Sergey Zakusin and Victoria Krupskaya
Minerals 2020, 10(12), 1121; https://doi.org/10.3390/min10121121 - 14 Dec 2020
Cited by 8 | Viewed by 2425
Abstract
The sorption of Cu2+ onto bentonite modified with Al Keggin cations and humic acid from CuCl2 solutions at pH 4.5 was studied. Modification of Na-bentonite with Al Keggin cations was found to result in an increase in the basal spacing of [...] Read more.
The sorption of Cu2+ onto bentonite modified with Al Keggin cations and humic acid from CuCl2 solutions at pH 4.5 was studied. Modification of Na-bentonite with Al Keggin cations was found to result in an increase in the basal spacing of montmorillonite from 1.29 nm for N-form to 1.85 and 1.78 nm for HAl13 and Al13 forms respectively, in a reduction of CEC (cation exchange capacity) and in the formation of additional sites with a variable charge with pHPZC 4.2. Al13-bentonite is not affected by heat. Under the conditions of the experiments at pH of 4.5 Na-bentonite adsorbs more Cu2+ from CuCl2 solutions then Al13 forms of bentonites. The main mechanism of copper sorption on Na-bentonite is the cation exchange Cu2+–Na+. The reduction of CEC of Na-bentonite after modification with Al Keggin cations leads to a decrease in the Cu2+ sorption. pH-dependent sorption sites on Al13-bentonites have a pHPZC of 4.2 and, therefore, under conditions of the experiment have positive charge which prevents Cu2+ sorption. Na-bentonite adsorbs more humic acid solution (HA) then Al13-bentonite and the proportion of adsorbed HA remains constant over the entire concentration range. Treatment of the Al13-bentonite with HA leads to the formation of the additional sorption sites. The amount of sorbed Cu2+ and the percentage of their extraction from solutions by HAAl13-bentonite is similar to those values for Na-bentonite. Full article
(This article belongs to the Special Issue Environmental Applications of Chemically Modified Clay Minerals)
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14 pages, 1780 KiB  
Article
Heavy Metals Content in the Soils of the Tatra National Park Near Lake Morskie Oko and Kasprowy Wierch—A Case Study (Tatra Mts, Central Europe)
by Joanna Korzeniowska and Paweł Krąż
Minerals 2020, 10(12), 1120; https://doi.org/10.3390/min10121120 - 13 Dec 2020
Cited by 17 | Viewed by 3256
Abstract
This paper presents the content of selected heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in the soils of the Tatra National Park (TNP). In order to determine the anthropogenic impact on the environment, the following coefficients were calculated: enrichment factors (EF), [...] Read more.
This paper presents the content of selected heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in the soils of the Tatra National Park (TNP). In order to determine the anthropogenic impact on the environment, the following coefficients were calculated: enrichment factors (EF), geoaccumulation index (Igeo), contamination factor (Cf), degree of contamination (Cd), and modified degree of contamination (mCd). It turned out that in the Kasprowy Wierch and Lake Morskie Oko test areas, the content of metals in the soil decreases with the increasing altitude above sea level. In both regions, the highest concentrations of cadmium and lead were found, for which the coefficients indicated significant environmental pollution. These metals, since they persist in the atmosphere for a long time and have a small particle diameter, can be moved over long distances. Long-range emission contributes to environmental contamination on a global scale. Under the influence of such emissions, even protected areas such as the Tatra National Park, considered to be of natural value, are exposed to the effects of human activities (industry in general, automotive industry in particular). Full article
(This article belongs to the Special Issue Elemental Concentration and Pollution in Soil, Water, and Sediment)
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22 pages, 7296 KiB  
Article
Effect of Stress Path on the Failure Envelope of Intact Crystalline Rock at Low Confining Stress
by Shantanu Patel and C. Derek Martin
Minerals 2020, 10(12), 1119; https://doi.org/10.3390/min10121119 - 13 Dec 2020
Cited by 9 | Viewed by 3149
Abstract
Numerical modelling is playing an increasing role in the interpretation of geological observations. A similar phenomenon is occurring with respect to the interpretation of the stress–strain response of intact rock measured in laboratory tests. In this research, the three-dimensional (3D) bonded particle model [...] Read more.
Numerical modelling is playing an increasing role in the interpretation of geological observations. A similar phenomenon is occurring with respect to the interpretation of the stress–strain response of intact rock measured in laboratory tests. In this research, the three-dimensional (3D) bonded particle model (BPM) with flat-jointed (FJ) contact was used to investigate the impact of stress paths on rock failure. The modified FJ contact model used for these studies numerically captured most of the intact rock behavior of Lac du Bonnet granite observed in the laboratory. A numerical simulation was used to track the behavior of this rock for different stress paths, starting with uniaxial tension and compression loading conditions. The migration from uniaxial tension to triaxial compression is challenging to simulate in physical laboratory tests but commonly observed around underground excavations. The numerical modelling methodology developed for this research tracks this stress path and the impact of the intermediate stress on peak strength at low confinements, commonly found around underground excavations. Full article
(This article belongs to the Special Issue The Hydro-Mechanics of Crystalline Rocks)
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10 pages, 4055 KiB  
Article
Kishonite, VH2, and Oreillyite, Cr2N, Two New Minerals from the Corundum Xenocrysts of Mt Carmel, Northern Israel
by Luca Bindi, Fernando Cámara, Sarah E. M. Gain, William L. Griffin, Jin-Xiang Huang, Martin Saunders and Vered Toledo
Minerals 2020, 10(12), 1118; https://doi.org/10.3390/min10121118 - 13 Dec 2020
Cited by 12 | Viewed by 4682
Abstract
Here, we describe two new minerals, kishonite (VH2) and oreillyite (Cr2N), found in xenoliths occurring in pyroclastic ejecta of small Cretaceous basaltic volcanoes exposed on Mount Carmel, Northern Israel. Kishonite was studied by single-crystal X-ray diffraction and was found [...] Read more.
Here, we describe two new minerals, kishonite (VH2) and oreillyite (Cr2N), found in xenoliths occurring in pyroclastic ejecta of small Cretaceous basaltic volcanoes exposed on Mount Carmel, Northern Israel. Kishonite was studied by single-crystal X-ray diffraction and was found to be cubic, space group Fm3¯m, with a = 4.2680(10) Å, V = 77.75(3) Å3, and Z = 4. Oreillyite was studied by both single-crystal X-ray diffraction and transmission electron microscopy and was found to be trigonal, space group P3¯1m, with a = 4.7853(5) Å, c = 4.4630(6) Å, V = 88.51 Å3, and Z = 3. The presence of such a mineralization in these xenoliths supports the idea of the presence of reduced fluids in the sublithospheric mantle influencing the transport of volatile species (e.g., C, H) from the deep Earth to the surface. The minerals and their names have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (No. 2020-023 and 2020-030a). Full article
(This article belongs to the Collection New Minerals)
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20 pages, 15405 KiB  
Article
Post-Magmatic Fluids Dominate the Mineralization of Dolomite Carbonatitic Dykes Next to the Giant Bayan Obo REE Deposit, Northern China
by Le Hu, Yike Li, Maoshan Chuan, Ruiping Li, Changhui Ke and Zhongjian Wu
Minerals 2020, 10(12), 1117; https://doi.org/10.3390/min10121117 - 12 Dec 2020
Cited by 2 | Viewed by 3182
Abstract
The Bayan Obo rare earth element (REE) deposit in Inner Mongolia, northern China, is the largest REE deposit in the world, whose mineralization process remains controversial. There are dozens of carbonatite dykes that are tightly related to the deposit. Here we report the [...] Read more.
The Bayan Obo rare earth element (REE) deposit in Inner Mongolia, northern China, is the largest REE deposit in the world, whose mineralization process remains controversial. There are dozens of carbonatite dykes that are tightly related to the deposit. Here we report the petrological and mineralogical characteristics of a typical dolomite carbonatite dyke near the deposit. The dolomite within the dyke experienced intense post-emplacement fluids metasomatism as evidenced by the widespread hydrothermal REE-bearing minerals occurring along the carbonate mineral grains. REE contents of bulk rocks and constituent dolomite minerals (>90 vol.%) are 1407–4184 ppm and 63–152 ppm, respectively, indicating that dolomite is not the dominant mineral controlling the REE budgets of the dyke. There are three types of apatite in the dyke: Type 1 apatite is the primary apatite and contains REE2O3 at 2.35–4.20 wt.% and SrO at 1.75–2.19 wt.%; Type 2 and Type 3 apatites are the products of replacement of primary apatite. The REE2O3 (6.10–8.21 wt.%) and SrO (2.83–3.63 wt.%) contents of Type 2 apatite are significantly elevated for overprinting of REE and Sr-rich fluids derived from the carbonatite. Conversely, Type 3 apatite has decreased REE2O3 (1.17–2.35 wt.%) and SrO (1.51–1.99 wt.%) contents, resulting from infiltration of fluids with low REE and Na concentrations. Our results on the dyke suggest that post-magmatic fluids expelled from the carbonatitic melts dominated the REE mineralization of the Bayan Obo deposit, and a significant fluid disturbance occurred but probably provided no extra REEs to the deposit. Full article
(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)
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