Minerals

18 pages, 3621 KiB

Open AccessArticle

The Problem of the Formation of Boehmite and Gibbsite in Bauxite-Bearing Lateritic Profiles

by Vladimir Mamedov, Natalia Boeva, Marina Makarova, Elena Shipilova and Philimon Melnikov

Minerals 2022, 12(3), 389; https://doi.org/10.3390/min12030389 - 21 Mar 2022

Cited by 9 | Viewed by 3007

The study of a large amount of factual material about the formation conditions of gibbsite or boehmite and their mutual transformations in lateritic bauxites allowed us to solve the problem of boehmite formation and its spatial and genetic relationship to gibbsite. The boehmite [...] Read more.

The study of a large amount of factual material about the formation conditions of gibbsite or boehmite and their mutual transformations in lateritic bauxites allowed us to solve the problem of boehmite formation and its spatial and genetic relationship to gibbsite. The boehmite formation occurred only during the formation of sedimentary-lateritic bauxites from alluvial and lacustrine sediments that underwent bleaching and resilification at the stage of sediment flooding, as well as on bleached bedrock under sedimentary-lateritic bauxites. The most intense boehmite formation occurred at a depth of 20–30 m from the surface and was accompanied by an alumina input, which was realized here in the form of boehmite along with the gibbsite formation due to the hydrolytic decomposition of kaolinite and partially due to the input alumina. In the upper profiles, the recrystallization of bauxites occurs with the replacement of dissolving boehmite with gibbsite, with a decrease in the total Al₂O₃ content and an increase in the amount of crystallization water. In classic lateritic bauxites, the boehmite content is highly insignificant; that is, its formation in them practically does not occur or is very much inhibited. Full article

(This article belongs to the Special Issue Biomineralization and Biominerals: Lessons from Mineral-Producing Organisms)

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18 pages, 9323 KiB

Open AccessArticle

Petrogenesis and Tectonic Setting of the Madeng Dacite, SW Sanjiang Indosinian Orogen: Evidence from Zircon U-Pb-Hf Isotopes, and Whole-Rock Geochemistry and Sr-Nd Isotopes

by Gang Huang, Liang-Liang Zhuang, Ya-Qi Yang, Li-Dan Tian, Wei Wu and Jin-Hong Liu

Minerals 2022, 12(3), 388; https://doi.org/10.3390/min12030388 - 21 Mar 2022

Cited by 1 | Viewed by 2004

Abstract

The Sanjiang Indosinian orogen, located in the eastern part of the Paleo-Tethys tectonic domain, is a critical region to study the Paleo-Tethyan Ocean evolution. Middle Permian–Late Triassic magmatic rocks are widespread in the Deqin–Weixi–Madeng area of southwestern (SW) Sanjiang Indosinian orogen, yet their [...] Read more.

The Sanjiang Indosinian orogen, located in the eastern part of the Paleo-Tethys tectonic domain, is a critical region to study the Paleo-Tethyan Ocean evolution. Middle Permian–Late Triassic magmatic rocks are widespread in the Deqin–Weixi–Madeng area of southwestern (SW) Sanjiang Indosinian orogen, yet their petrogenesis and tectonic setting remain disputed. In this study, LA-ICP-MS zircon U-Pb age and Hf isotopes, and whole-rock elemental and Sr-Nd isotope geochemistry of Madeng dacite were studied. The Madeng dacite was dated at ca. 241.7 and 243.4 Ma. The samples had high Al₂O₃ (12.91 to 14.39 wt.%) but low MgO (0.62 to 1.76 wt.%) contents, and were alkali-rich (Na₂O + K₂O = 6.97 to 8.66 wt.%) with A/CNK > 1.1, strongly resembling peraluminous S-type granites. The rocks were enriched in Rb, K, Th, U and LREE, but depleted in Ba, Sr, Nb, Ta, P and Ti, and showed obvious negative Eu anomalies, suggesting fractionation of Ti-bearing minerals (e.g., rutile and ilmenite) and plagioclase. The dacite had an initial ⁸⁷Sr/⁸⁶Sr value of 0.705698 to 0.710277, and negative ε_Nd(t) (−11.28 to −10.64) and ε_Hf(t) (−13.99 to −8.60), indicating a continental meta-sedimentary source. Their average Nb/Ta (12.24) and Th/U (4.65) were also consistent with continental crust. According to the lithological assemblage and geochemical features, we propose that the Deqin–Weixi–Madeng area intermediate-felsic magmatism was generated in a subduction-related tectonic setting. Full article

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13 pages, 3116 KiB

Open AccessArticle

Atomic Model of Gold Adsorption onto the Pyrite Surface with DFT Study

by Chunlin Liu, Yongbing Li, Qi Cheng and Yang Zhao

Minerals 2022, 12(3), 387; https://doi.org/10.3390/min12030387 - 21 Mar 2022

Cited by 4 | Viewed by 2447

Abstract

Adsorption mineralization of gold is an important mineralization mechanism under epigenetic and low temperature conditions. In this paper, a plane-wave pseudopotential method based on density functional theory (DFT) is used to explore the adsorption mechanism of gold on the surface of pyrite. Among [...] Read more.

Adsorption mineralization of gold is an important mineralization mechanism under epigenetic and low temperature conditions. In this paper, a plane-wave pseudopotential method based on density functional theory (DFT) is used to explore the adsorption mechanism of gold on the surface of pyrite. Among the three surfaces of pyrite, the surface energies of (100), (111), and (210) surfaces are 1.0508, 1.5337, and 1.8255 J∙m², respectively, and the (100) surface is the most stable surface in the thermodynamic state. The adsorption capacities of gold atoms under different surfaces are (210) (−2.68 eV) > (111) (−1.67 eV) > (100) (−0.84 eV). Mulliken analysis indicates that charge transfer occurs after the adsorption of gold atoms onto the surface of pyrite (210), and gold and iron atoms are oxidized with the reduction of sulfur atoms. The density of states (PDOS) analysis shows that the 5d orbital on the Fermi energy level of the iron atom is active and the adsorption capacity is greater than that of the sulfur atom, and adsorption is formed between the gold atom, which leads to the gold being able to be stably deposited on the surface of pyrite (210). Full article

(This article belongs to the Special Issue 3D-Modelling of Crustal Structures and Mineral Deposit Systems)

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13 pages, 4639 KiB

Open AccessArticle

Study of Synthetic Titania Slags Demonstrating Characteristics Similar to High Titania Ilmenite Slag

by Avishek Kumar Gupta, Matti Aula, Harisankar Sreenivasan, Pasi Mäkelä, Marko Huttula and Timo Fabritius

Minerals 2022, 12(3), 386; https://doi.org/10.3390/min12030386 - 20 Mar 2022

Viewed by 1732

Abstract

The upgradation of the ilmenite ore, using a pyrometallurgy method, is performed using a carbothermic reduction of the ilmenite. A high titania slag is obtained which is used as a feedstock for the TiO₂ pigment production. The slag is cooled after tapping [...] Read more.

The upgradation of the ilmenite ore, using a pyrometallurgy method, is performed using a carbothermic reduction of the ilmenite. A high titania slag is obtained which is used as a feedstock for the TiO₂ pigment production. The slag is cooled after tapping in big molds and can take ten days to cool. This cooling method has remained the same since the inception of ilmenite smelting and recently rapid cooling through granulation has been utilized. The work presented in this paper focuses on the microstructural study of the slags that were prepared using different techniques and cooled at different cooling rates. Various analytical techniques, such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and X-ray photoelectron spectroscopy (XPS) were used to exhibit the similarity of these synthetic slags to the properties of high titania ilmenite slag. The slag consisted mostly of pseudo-brookite phase with a M₃O₅ stoichiometry and smaller amounts of silicate and rutile phase. A glassy phase of silica was observed and most of the impurities were found to be present in the silicate phase. These silica phases were observed to be separate from the pseudo-brookite phase and along the phase boundaries. Micro-cracking of the slag surface, which is the characteristic of the M₃O₅ phase formed in the ilmenite slag, were observed under the SEM analysis. The XPS analysis revealed that faster cooling does result in lower amount of oxidation but the difference in the TiO₂ and Ti₂O₃ composition can have larger impact on oxidation than the cooling speed. Full article

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

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16 pages, 5295 KiB

Open AccessArticle

Influence of Urbanization on Groundwater Chemistry at Lanzhou Valley Basin in China

by Xiaoli Lü, Zhantao Han, Haijun Li, Yuejun Zheng and Jingtao Liu

Minerals 2022, 12(3), 385; https://doi.org/10.3390/min12030385 - 20 Mar 2022

Cited by 6 | Viewed by 2007

Abstract

With the rapid development of the economy, urbanization and industrialization gradually become an important driving force of groundwater chemical evolution. In this study, Lanzhou City, which is one of the biggest industrial cities in northwest China, was selected to investigate the impacts of [...] Read more.

With the rapid development of the economy, urbanization and industrialization gradually become an important driving force of groundwater chemical evolution. In this study, Lanzhou City, which is one of the biggest industrial cities in northwest China, was selected to investigate the impacts of city development on groundwater quality. Several hydrochemical methods together with principal component analysis (PCA) were used for the hydrochemistry evolution characteristics and sensitive factors of groundwater chemistry in different urban functional areas of Lanzhou City. The results show that 96% of the groundwater in the study area cannot meet the groundwater quality standards of China. The main factors affecting the quality are SO₄²⁻, TDS, total hardness, Mg²⁺ and Na⁺. Urbanization and industrialization lead to further deterioration of the already naturally high TDS groundwater. NO₃⁻, Cl⁻ and NH₄⁺ are the characteristic factors of human input sources for commercial residential areas; total Fe and NO₃⁻ are the characteristic factors of new urban areas in the urban-rural junction; and SO₄²⁻, NO₃⁻, Cl⁻, Total Fe, Mn²⁺, F⁻, I⁻, Pb²⁺, Cr⁶⁺ and As³⁺ are the characteristic factors of industrial areas. Domestic sewage infiltration and manure infiltration are the main driving factors of groundwater quality deterioration in commercial residential areas. Nitrate fertilizer infiltration and sewage irrigation are the main factors leading to the increase in nitrate nitrogen in groundwater in the new urban area. Industrial wastewater leakage and organic pollution that promote the dissolution of minerals in the aquifer (the dissolution of fluorine-containing minerals and reductive dissolution of iron manganese oxides) are the main driving factors for the deterioration of groundwater quality in the petrochemical industrial area. Full article

(This article belongs to the Special Issue Challenges of Groundwater Quality Degradation in the Past Decades: Clues from Water–Minerals Interaction)

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19 pages, 5809 KiB

Open AccessArticle

A Comprehensive Recovery Process for Selective Separation and Enrichment of Copper, Zinc and Iron Minerals from a Polymetallic Ore and the Adsorption Mechanism of Collector Z-200

by Bin Xu, Shouguo Zhong, Jintian Wu, Yujuan Zhou, Yongbin Yang, Qian Li and Tao Jiang

Minerals 2022, 12(3), 384; https://doi.org/10.3390/min12030384 - 19 Mar 2022

Cited by 2 | Viewed by 2632

Abstract

A comprehensive recovery process for the selective separation and enrichment of copper, zinc and iron minerals from a polymetallic ore was developed, which consisted of copper flotation, zinc flotation, and iron magnetic separation, and the adsorption mechanism of the copper collector Z-200 (O-isopropyl-N-ethyl [...] Read more.

A comprehensive recovery process for the selective separation and enrichment of copper, zinc and iron minerals from a polymetallic ore was developed, which consisted of copper flotation, zinc flotation, and iron magnetic separation, and the adsorption mechanism of the copper collector Z-200 (O-isopropyl-N-ethyl thionocarbamate) was also studied in this work. The contents of the main valuable metallic elements of Cu, Zn and Fe in the ore were respectively 0.61%, 1.68% and 14.17%, and they mainly existed as chalcopyrite, sphalerite and magnetite, whose dissemination relationship was complex. Under the optimal conditions of this process, the recoveries of Cu, Zn and Fe in their respective concentrates reached 86.1%, 87.6% and 77.8%, and their grades were separately 20.31%, 45.97% and 63.39%. This process realized the selective separation and beneficiation of copper, zinc, and iron minerals from the ore, and had promising industrial application prospects. The adsorption configuration analysis demonstrated that the steadiest adsorption configurations of Z-200 on the surfaces of chalcopyrite, sphalerite and magnetite were the simultaneous adsorption of carbonyl S together with the O atom. Compared with sphalerite and magnetite, Z-200 was more prone to adsorb on the chalcopyrite surface. The Mulliken charge population and bond length analyses manifested that Z-200 chemically adsorbed on the chalcopyrite surface by forming a normal covalent bond and a back donation covalent bond, and the normal covalent bond played a leading role. The chemisorption of Z-00 was supported by the FTIR spectrum analysis result. Full article

(This article belongs to the Special Issue Mineral Processing and Extractive Metallurgy of Sulfide Ores)

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30 pages, 11137 KiB

Open AccessArticle

The Early Paleozoic Tectonic Framework and Evolution of Northern West Qinling Orogen: By Zircon U-Pb Dating and Geochemistry of Rocks from Tianshui and Sunjiaxia

by Zhen Liu, Wei Xu, Chunming Liu, Yujia Xin and Dezhi Huang

Minerals 2022, 12(3), 383; https://doi.org/10.3390/min12030383 - 19 Mar 2022

Viewed by 2282

Abstract

The Tianshui-Sunjiaxia area is located in the connection zone of West Qinling Orogen and North Qilian Orogen, which could provide great insights into the amalgamation processes between the northern and southern blocks of China. Three subduction- and rift-related rocks gneissic granite from North [...] Read more.

The Tianshui-Sunjiaxia area is located in the connection zone of West Qinling Orogen and North Qilian Orogen, which could provide great insights into the amalgamation processes between the northern and southern blocks of China. Three subduction- and rift-related rocks gneissic granite from North Qilian arc-interarc belt (NQAI) granite and metabasalt from North Qinling back-arc basin (NQBA) are distinguished across the connection zone. The gneissic granite was generated by melts from older crustal materials of Longshan Group with the addition of a relatively juvenile basaltic source from the lower crust during the collision process. The Liwanxincun metabasalt reflects the mixing of the partial melting of the shallow asthenospheric mantle and the metasomatized mantle in a back-arc extension setting. The LA-ICP-MS zircon U-Pb dating of gneissic granite (068, 069) yields crystallization ages of 457.0 ± 1.6 Ma and 445.9 ± 2.1 Ma. The study area is divided into six tectonic units in Early Paleozoic time involving NQAI (Yanjiadian-Xinjie) continental arc, interarc rift basin (Maojiamo-Xiwali), continental arc (Chenjiahe-Wangjiacha); NQBA back-arc rift basin (Huluhe-Hongtubao), island arc and ophiolitic melange belt (North Qinling-Shangdan). A tectonic model is proposed in which the NQAI continental arc (Yanjiadian-Xinjie) might represent the early period of subduction of North Qilian Ocean (NQO) and the interarc rift is the product of the extension triggered by southward subduction of NQO. The ongoing subduction of NQO then leads to the formation of Chenjiahe-Wangjiacha continental arc, as well as the Hongtubao back-arc spreading ridge in NQBA back-arc basin (Huluhe). The tectonic evolution of the connection zone is closely associated with the closure of the North Qilian Ocean and North Qinling-Shangdan Ocean in the context of the convergence process of micro-continental blocks, including North China block, Longshan group and North Qinling Terrane. Full article

(This article belongs to the Special Issue Granitic Intrusion and Related Mineralization in Asia)

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18 pages, 7234 KiB

Open AccessArticle

Iron Ore Tailing Composition Estimation Using Fused Visible–Near Infrared and Thermal Infrared Spectra by Outer Product Analysis

by Nisha Bao, Haimei Lei, Yue Cao, Shanjun Liu, Xiaowei Gu, Bin Zhou and Yanhua Fu

Minerals 2022, 12(3), 382; https://doi.org/10.3390/min12030382 - 19 Mar 2022

Cited by 4 | Viewed by 2398

Abstract

Iron ore tailings are mainly composed of SiO₂ and iron, whose content determines the potential reuse strategy of the tailings. Compared with the traditional wet chemistry approach, spectroscopy has proven its superior effectiveness in characterizing and predicting minerals, such as iron oxides, [...] Read more.

Iron ore tailings are mainly composed of SiO₂ and iron, whose content determines the potential reuse strategy of the tailings. Compared with the traditional wet chemistry approach, spectroscopy has proven its superior effectiveness in characterizing and predicting minerals, such as iron oxides, clay, and SiO₂. This study aims to estimate the content of SiO₂ and TFe in iron ore tailings based on visible–near infrared (VIS–NIR, 350–2500 nm) and thermal infrared (TIR, 8–14 μm) spectroscopy. The outer product analysis (OPA) method is used to combine VIS–NIR and TIR spectral domains, from which an outer product matrix of fusion data can be generated. The study area is the iron ore tailing dam from Waitoushan, which is one of the super-large iron deposits in the Anshan–Benxi iron cluster of northeastern China. The spectral analysis results demonstrated the following: (1) The reflectance feature at 1163–2499 nm in the VIS–NIR range correlates with TFe and the emissivity feature at 8–9.4 and 10.7–12 μm in the TIR range correlates with SiO₂. (2) Compared with the original absorbance spectra, the correlation coefficients of fusion spectra improve from 0.66 to 0.87 for TFe and from 0.64 to 0.84 for SiO₂. (3) The partial least squares regression, random forest (RF), and extreme learning machine exploiting particle swarm optimization modeling methods are established for SiO₂ and TFe estimation. The prediction accuracy results indicate that the prediction model with OPA-fused spectra performs significantly better than with individual VIS–NIR and TIR spectra. The RF model with input-fused spectra provides the highest accuracy with the coefficients of determination of 0.95 and 0.91, root mean square errors of 0.97% and 0.96%, and ratios of performance to interquartile distance of 6.49 and 2.31 for SiO₂ and TFe content estimation, respectively. These outcomes provide a theoretical basis and technical support for tailing composition estimation using spectroscopy. Full article

(This article belongs to the Special Issue Mapping of Rocks and Minerals Using Hyperspectral Remote Sensing)

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23 pages, 8148 KiB

Open AccessArticle

Deconstructing the Iron Boomerang—Quantitative Predictions of Hematite, Ochreous, and Vitreous Goethite Mixtures

by Andrew Rodger and Erick Ramanaidou

Minerals 2022, 12(3), 381; https://doi.org/10.3390/min12030381 - 19 Mar 2022

Viewed by 2092

Abstract

The so-called iron boomerang is constructed by using a combination of spectral metrics derived from the 900 nm ⁶A₁→⁴T₁ Fe³⁺ crystal field absorption. Previous work showed the iron boomerang provides qualitative information about the mineralogical type [...] Read more.

The so-called iron boomerang is constructed by using a combination of spectral metrics derived from the 900 nm ⁶A₁→⁴T₁ Fe³⁺ crystal field absorption. Previous work showed the iron boomerang provides qualitative information about the mineralogical type of spectral datasets of Western Australian iron ore deposits. That work is expanded to demonstrate how the shape of the iron boomerang is driven by a linear mixing regime between hematite and ochreous and vitreous goethite. The iron boomerang enveloping shape is defined by mixing pathways between 3 different 2-endmember systems of hematite–ochreous goethite, hematite–vitreous goethite and ochreous–vitreous goethite and a 3-endmember mixing regime in the interior of the boomerang. This provides a novel methodology of quantifying the relative hematite, ochreous, and vitreous goethite content from spectrally derived data. A combination of 4 spectral metrics as input features to a random forest regression model results in modelling root mean squared errors (RMSE) of approximately 4% when all endmembers are known and in a system where the endmembers are not known the RMSE is approximately 10%. Additionally, a means of identifying potential hematite endmembers from a spectral dataset is presented. Lastly, the regression models are applied to 3 iron ore diamond drillcore from the Hamersley Province in Western Australia and demonstrates that the proportions of hematite, ochreous, and vitreous goethite can be estimated downhole which, in turn, provides ore zone delineation and hardcap and hydrated zone identification. Full article

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24 pages, 4553 KiB

Open AccessFeature PaperArticle

Feeding Material Identification for a Crusher Based on Deep Learning for Status Monitoring and Fault Diagnosis

by Yongtai Pan, Yankun Bi, Chuan Zhang, Chao Yu, Zekui Li and Xi Chen

Minerals 2022, 12(3), 380; https://doi.org/10.3390/min12030380 - 19 Mar 2022

Cited by 7 | Viewed by 2394

Abstract

In large coal preparation plants with a capacity of 30 million tons/year, the belt speed can reach 7 m/s and the thickness of the material layer can reach 500 mm. Therefore, in high-throughput and complex environments, the problem exists that harmful feeding materials [...] Read more.

In large coal preparation plants with a capacity of 30 million tons/year, the belt speed can reach 7 m/s and the thickness of the material layer can reach 500 mm. Therefore, in high-throughput and complex environments, the problem exists that harmful feeding materials such as iron and gangue are not easily detected, and thus fault diagnosis in the crushers lags behind. Therefore, it is necessary to extract the equipment operation signals from the noisy production environment and identify the feeding materials. Currently, there is no systematic research on signal processing and image classification of crusher feeding materials, while the convolutional neural network (CNN) is outstanding in computer vision. In this paper, sound and vibration signals of the feeding materials are denoised by spectral subtraction and transformed into feature images by continuous wavelet transforms. Then, an image classification model based on CNN is built for these feature images to study its classification mechanism and performance. The results show that the model classification accuracy is respectively 84.0%, 93.5% and 80.1% in coal–iron–wood classification, coal–iron classification, and coal–wood classification. The good classification performance for coal, iron and wood can satisfy the practical demands to remove the harmful feeding materials, which provides the core technical support for the establishment of operating status monitoring and fault diagnosis system of crushing equipment. Full article

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

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23 pages, 6725 KiB

Open AccessArticle

Fractional Crystallization and Partial Melting of the Paleoproterozoic Gneisses and Pegmatite in the Giant Husab Uranium Deposit, Namibia

by Shan-Shan Li, Wei Zeng, Huai-Feng Zhang, Lu Wang, Espine Tuyakula Shivute and Kun-Feng Qiu

Minerals 2022, 12(3), 379; https://doi.org/10.3390/min12030379 - 19 Mar 2022

Cited by 2 | Viewed by 2519

Abstract

The giant Husab uranium deposit is located in the Paleoproterozoic Abbabis Metamorphic Complex, which was highly partially melted and metamorphosed during the Damara Orogenic Event. The timing of magma emplacement has been investigated; however, the petrogenesis is unclear. Here we reported petrology, geochemistry, [...] Read more.

The giant Husab uranium deposit is located in the Paleoproterozoic Abbabis Metamorphic Complex, which was highly partially melted and metamorphosed during the Damara Orogenic Event. The timing of magma emplacement has been investigated; however, the petrogenesis is unclear. Here we reported petrology, geochemistry, and monazite U-Pb age data from biotite granitic gneisses, syeno-granite, syeno-granitic pegmatites, syeno-granitic gneiss, granitic syenite and biotite quartz monzonites of this complex. Geochemical data suggest that these Paleoproterozoic rocks show high SiO₂, Al₂O₃, and K₂O, moderate Na₂O, low CaO and Fe₂O₃, and MgO abundance. The alkali-calcic to alkalic, peraluminous, low Fe-number, depletion in HFSE (Nb-Ta, Ti) and enrichment in LILE (e.g., Rb, Pb) characteristic correspond with I- and S-type granite. Major and trace elements are strongly fractionated with the increase of SiO₂, which, together with strongly fractionated LREE patterns and high (La/Yb)_N ratios of the biotite granitic gneiss and syeno-granitic gneiss, suggest that the magma was highly evolved and fractionated. Monazite U-Pb data show three metamorphic age groups of 581–535 Ma, 531–522 Ma and 518–484 Ma. The increasing trend of La/Sm and La/Yb with the increase of La, suggest these rocks most likely experienced a partial melting process during the late Palaeozoic metamorphism. We, thus, propose a fractional crystallization model for the generation of the Paleoproterozoic Abbabis Metamorphic Complex basement rock, which was metamorphosed and melted during the late Palaeozoic Damara Orogenic Event and provided the magma sources for primary uranium mineralization. Full article

(This article belongs to the Special Issue Understanding Hydrothermal Ore Deposits: Insights from In-situ Analyses)

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14 pages, 3677 KiB

Open AccessArticle

Preliminary Mineralogical Characterization of Branching Selenite Gypsum: New Insights for the Paleoenvironmental Reconstruction and Mechanical Characterization

by Chiara Caselle, Linda Pastero, Simona Cavagna and Sabrina Bonetto

Minerals 2022, 12(3), 378; https://doi.org/10.3390/min12030378 - 19 Mar 2022

Cited by 1 | Viewed by 1825

Abstract

The present study proposes a characterization of textural and mineralogical features of branching selenite gypsum lithofacies from the Monferrato area (NW Italy). This facies is considered to have appeared during the sequence of the primary lower gypsum of the Messinian Salinity Crisis starting [...] Read more.

The present study proposes a characterization of textural and mineralogical features of branching selenite gypsum lithofacies from the Monferrato area (NW Italy). This facies is considered to have appeared during the sequence of the primary lower gypsum of the Messinian Salinity Crisis starting from the sixth stratigraphical cycle, providing a useful tool for stratigraphic correlation throughout the Mediterranean. It is often associated with thick and continuous beds that are exploited by open-pit and underground quarries. We provide the results of a characterization of the non-gypsum minerals that represent approximately 10% in weight of the rock. Mineralogical data were collected with energy-dispersive X-ray spectroscopy (EDS) and X-ray powder diffraction (XRPD) techniques. In addition, a detailed characterization of clay families was performed through dedicated XRPD analyses. Results highlight the presence of detrital minerals (quartz, feldspars and clay minerals), calcite, dolomite and epsomite. Clay analysis registered the existence of five different families (illite, chlorite, smectite and two mixed layers). These mineralogical data suggest that the origin of this lithofacies is connected to both depositional processes and in situ precipitation processes under different conditions of saturation of the brine (respectively undersaturated and supersaturated in sulfates). The mineralogical and textural heterogeneity also represents an important element in controlling the mechanical response of the material and the consequent stability of quarry sites. Full article

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

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23 pages, 5329 KiB

Open AccessArticle

A Combined EMPA and LA-ICP-MS Study of Muscovite from Pegmatites in the Chinese Altai, NW China: Implications for Tracing Rare-Element Mineralization Type and Ore-Forming Process

by Qifeng Zhou, Kezhang Qin, Dongmei Tang and Chunlong Wang

Minerals 2022, 12(3), 377; https://doi.org/10.3390/min12030377 - 18 Mar 2022

Cited by 5 | Viewed by 3258

Abstract

The mineralogical studies of rare-element (REL) pegmatites are important for unraveling the ore-forming process and evaluating REL mineralization potential. The Chinese Altai orogenic belt hosting more than 100,000 pegmatite dykes is famous for rare-metal resources worldwide and diverse REL mineralization types. In this [...] Read more.

The mineralogical studies of rare-element (REL) pegmatites are important for unraveling the ore-forming process and evaluating REL mineralization potential. The Chinese Altai orogenic belt hosting more than 100,000 pegmatite dykes is famous for rare-metal resources worldwide and diverse REL mineralization types. In this paper, we present the results of EMPA and LA-ICP-MS for muscovite from the typical REL pegmatite dykes of the Chinese Altai. The studied pegmatites are Li-Be-Nb-Ta, Li-Nb-Ta, Nb-Ta, Be-Nb-Ta, Be and barren pegmatites. The Li⁺ accompanied with Fe, Mg and Mn substitute for Al³⁺ at the octahedral site in muscovite from the REL pegmatites, and the substitution of Rb by Cs at the interlayer space is identified in muscovite from the Be pegmatites. The P and B contents increase with evolution degree and the lenses from the Nb-Ta pegmatite are produced at late fluid-rich stage with high fluxes (P and B). The enrichment of HFSE in muscovite indicates a Nb-Ta-Sn-W rich pegmatite magma for the Be-Nb-Ta pegmatite. From barren pegmatite, beryl-bearing zone, to spodumene-bearing zone, the evolution degrees of pegmatite-forming magmas progressively increase. In the Chinese Altai, the possible indicators of muscovite for REL mineralization types include Rb (ca. 400–600 ppm, barren pegmatite; ca. 1200–4000 ppm, Be pegmatite; >4500 ppm, Li pegmatite), Cs (ca. 5–50 ppm, barren pegmatite; ca. 100–500 ppm, Be pegmatite; >300 ppm, Li pegmatite) and Ge (<3 ppm, barren pegmatite; ca. 4–6 ppm, Be pegmatite; ca. 6–12 ppm, Li pegmatite) coupled with Ta, Be (both <10 ppm, barren pegmatite) and FeO (ca. 3–4 wt%, Be pegmatite; ca. 1–2.5 wt%, Li pegmatite). The plots of Nb/Ta vs. Cs and K/Rb vs. Ge are proposed to discriminate barren, Be- and Nb-Ta-(Li-Be-Rb-Cs) pegmatites. The Li, Be, Rb, Cs and F concentrations of forming liquid are evaluated based on the trace element compositions of muscovite. The high Rb and Cs contents of liquid and lower Be contents than beryl saturation value indicate that both highly evolved pegmatite magma and low temperature at emplacement contribute to beryl formation. The liquids saturated with spodumene have large variations of Li, possibly related to metastable state at Li unsaturation–supersaturation or heterogeneous distribution of lithium in the system. Full article

(This article belongs to the Special Issue Rare Metal Ore Formations and Rare Metal Metallogeny)

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19 pages, 3354 KiB

Open AccessArticle

Rehabilitation of Disturbed Lands with Industrial Wastewater Sludge

by Tatyana A. Petrova, Edelina Rudzisha, Alexey V. Alekseenko, Jaume Bech and Mariya A. Pashkevich

Minerals 2022, 12(3), 376; https://doi.org/10.3390/min12030376 - 18 Mar 2022

Cited by 24 | Viewed by 3196

Abstract

Wastelands of the mining industry are among the largest of disturbed areas that demand revitalization. To reduce environmental impact and to better manage these geo-resources, the formation of sustainable plant and soil complexes and the restoration of self-recovery soil function are critical points. [...] Read more.

Wastelands of the mining industry are among the largest of disturbed areas that demand revitalization. To reduce environmental impact and to better manage these geo-resources, the formation of sustainable plant and soil complexes and the restoration of self-recovery soil function are critical points. The successful return of vegetative cover at post-mining sites requires eliminating the deficiency of organic matter. For this, we assessed the usability of non-traditional ameliorants to provide a better understanding of benefits from mutual dependencies of environmental resources. To prevent losses and to close resource cycles, we studied the applicability of wastewater sludge from the pulp and paper (SPP) industry as an amendment to counteract soil degradation and rehabilitate human-disturbed lands. Waste rock limestone, beresite, and phosphogypsum substrates of post-mining sites were used in vitro for the application of sludge and peat mixture and consequent grass seeding. The formed vegetative cover was analyzed to compare the germination and biomass growth on reconstructed soils. We assessed the efficiency of ameliorant combinations by two approaches: (1) the traditional technique of cutting-off plant material to measure the obtained plant biomass, and (2) digital image analysis for RGB-processed photographs of the vegetative cover (r² = 0.75–0.95). The effect of SPP on plant cover biomass and grass height showed similar results: land rehabilitation with the formation of a 20 cm soil layer on mine waste dumps was environmentally suitable with an SPP:soil ratio of 1:3. However, excessive application (ratio 1:1 of SPP to the soil) negatively affected seed germination and plant vegetation. Full article

(This article belongs to the Special Issue Application of Mineral-Based Amendments, Volume II)

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13 pages, 6438 KiB

Open AccessArticle

Study on Fracture and Seepage Evolution Law of Stope Covered by Thin Bedrock under Mining Influence

by Zhaolin Li, Lianguo Wang, Ke Ding, Bo Ren, Shuai Wang, Chongyang Jiang and Zhiyuan Pan

Minerals 2022, 12(3), 375; https://doi.org/10.3390/min12030375 - 18 Mar 2022

Cited by 4 | Viewed by 1827

Abstract

Aiming to better understand the fracture evolution characteristics of thin bedrock affected by mining, a program was developed to establish a numerical calculation model for the fracture evolution of the overlying rock in the stope under the coupled seepage-stress condition. The fracturing law [...] Read more.

Aiming to better understand the fracture evolution characteristics of thin bedrock affected by mining, a program was developed to establish a numerical calculation model for the fracture evolution of the overlying rock in the stope under the coupled seepage-stress condition. The fracturing law of mining overburden during the advancing process of the coal seam working face has been deeply studied. The dynamic change process of the development height of the overburden fissure zone is analyzed. The results show that with the advance of the working surface, shear and tension compound rupture occurs in the overlying rock layer bottom-up. The rupture penetrates into the sand-water layer and forms a stable rupture zone, which terminates at the bottom of the clay layer in the vertical direction and no longer develops upward. The equivalent stress concentration area is obviously separated at the bottom of the clay layer. Additionally, there is no obvious damage to the clay layer, indicating that the integrity of the clay layer has been protected. This pattern is consistent with the field monitoring results. Under the dual action of mining stress and pore water pressure, the bedrock aquifer ruptured in a wide range, and gradually caused water to flow to the goaf. The low pore pressure zone runs through the entire bedrock layer and ends at the bottom of the clay layer; also, the effective velocity of pore fluid shows a consistent pattern. The on-site water inflow monitoring results found that the main source of water inflow was the sandstone aquifer in the bedrock section, and the shallow groundwater and surface water did not enter the working face in large quantities with coal mining. This shows that the clay layer has a good water barrier effect, effectively blocking the inflow of shallow groundwater or surface water into the working face. It also shows that the “soft–hard” roof layer combination feature greatly buffers the impact of mining on the water isolation layer and has a good water separation effect. Full article

(This article belongs to the Special Issue Green Mining of Coal Mine in China)

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12 pages, 1790 KiB

Open AccessArticle

Optimization of Parameters for Rheological Properties and Strength of Cemented Paste Backfill Blended with Coarse Aggregates

by Jiandong Wang, Aixiang Wu, Zhuen Ruan, Raimund Bürger, Yiming Wang, Shaoyong Wang, Pingfa Zhang and Zhaoquan Gao

Minerals 2022, 12(3), 374; https://doi.org/10.3390/min12030374 - 18 Mar 2022

Cited by 7 | Viewed by 1912

Abstract

Cemented paste backfill (CPB) technology is widely used for environmental protection and underground goaf treatment. The influences of solid concentration, coarse aggregates dosage, and cement dosage on the rheological properties and compressive strength of CPB blended with coarse aggregates (CA-CPB) are investigated through [...] Read more.

Cemented paste backfill (CPB) technology is widely used for environmental protection and underground goaf treatment. The influences of solid concentration, coarse aggregates dosage, and cement dosage on the rheological properties and compressive strength of CPB blended with coarse aggregates (CA-CPB) are investigated through three-factor and four-level orthogonal experiments. The dynamic shear stress and plastic viscosity are selected to characterize the rheological properties of CA-CPB. The uniaxial compressive strength (UCS) is used to describe the compressive strength. The effect of each factor on rheological properties is different from that on UCS. The most significant influences on rheological properties and UCS are solid concentration and cement dosage, respectively. The optimal levels of each factor for rheological properties and UCS are different, resulting in different optimal combinations obtained through range analysis. Therefore, the overall desirability function approach is employed to perform multiple response optimization. The optimal parameters for high fluidity and strength obtained provide valuable information for the CA-CPB process in the Chifeng Baiyinnuoer Lead and Zinc Mine. Full article

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

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11 pages, 1105 KiB

Open AccessArticle

Geochemical Study of the Iron Age Settlement Occupational Layer and the Early Roman Time Agricultural Layer at Voorthuizen, The Netherlands

by Olga Druzhinina, Laura Gedminienė and Kasper van den Berghe

Minerals 2022, 12(3), 373; https://doi.org/10.3390/min12030373 - 18 Mar 2022

Cited by 4 | Viewed by 1837

Abstract

The application of geochemical analysis in archaeology provides a better understanding of ancient human activities. This paper presents the results of geochemical multi-element, LOI, MS, and geochronological analyses of a cultural layer at the Voorthuizen (The Netherlands) archaeological site. The study has revealed [...] Read more.

The application of geochemical analysis in archaeology provides a better understanding of ancient human activities. This paper presents the results of geochemical multi-element, LOI, MS, and geochronological analyses of a cultural layer at the Voorthuizen (The Netherlands) archaeological site. The study has revealed a difference in the geochemical composition of an occupational surface in the Iron Age settlement and an early Roman Time agricultural horizon. The former is enriched in Ba, Sr, Rb, Th, Cl, and Mg, while the latter displays elevated P, Pb, Ni, Mn, and V values. The study has provided a deeper insight into the agricultural techniques applied at the Voorthuizen site and on the so-called Celtic Fields, known as ancient field systems dating from the same period and widespread throughout north-west Europe. It seems that household waste was not used as a fertilizer at Voorthuizen, while the application of manure is characteristic of Celtic Fields. However, phosphorous values in the Voorthuizen agricultural horizon are comparable to those in the Celtic Fields, suggesting similar sources of P in both cases. Elevated Si and “mobile” Fe, Mn, V, Pb, As, and Sn, along with higher MS measurements, are indicative of the use of extra mineral matter for the fertilization of the Voorthuizen ancient arable field. Full article

(This article belongs to the Special Issue Environment and Geochemistry of Sediments)

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18 pages, 22480 KiB

Open AccessArticle

Responses of Pre-Holed Granite under Coupled Biaxial Loading and Unloading Stress Condition

by Zilong Zhou, Zizi Pi, Yue Jing and Shaofeng Wang

Minerals 2022, 12(3), 372; https://doi.org/10.3390/min12030372 - 17 Mar 2022

Cited by 2 | Viewed by 1651

Abstract

Underground excavation is a necessary process for constructing mines, tunnels and depots in granite rock mass. In this study, the numerical granite specimens were established by the discrete element method and confirmed by laboratory experiments in order to investigate the peak stress, cracking [...] Read more.

Underground excavation is a necessary process for constructing mines, tunnels and depots in granite rock mass. In this study, the numerical granite specimens were established by the discrete element method and confirmed by laboratory experiments in order to investigate the peak stress, cracking development and failure properties of pre-holed granite under coupled biaxial loading and unloading conditions. The results show that, for the specimens containing D-type and square holes, the peak biaxial unloading strengths first decrease, then increase and finally decrease as the inclination angles of the holes increase. For the specimens with elliptical holes, the peak biaxial unloading strengths first decrease and then increase with the increases in the inclination angles of the holes. The biaxial unloading strengths of specimens containing elliptical, circular, D-type and square holes decrease in that order. The cracks initially appear near the crossover points between the X-type shear fracturing plane and the pre-hole in the center and gradually expand along the X-type shear direction, which indicates that the failure of pre-holed granite is primarily shear failure. When the overall length of cracks expanding along the X-type shear direction extends to the size of the pre-hole in the center, the failure of the pre-holed specimen occurs. When the existing pre-hole in the center of the granite specimen extends to connect with the shear slip in the vicinity of the hole, this triggers overall failure. Full article

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15 pages, 3755 KiB

Open AccessArticle

Characterization of Monochromate and Hemichromate AFm Phases and Chromate-Containing Ettringite by ¹H, ²⁷Al, and ⁵³Cr MAS NMR Spectroscopy

by Shuai Nie and Jørgen Skibsted

Minerals 2022, 12(3), 371; https://doi.org/10.3390/min12030371 - 17 Mar 2022

Cited by 2 | Viewed by 2223

Abstract

The calcium aluminate hydrate AFm and AFt phases formed upon hydration of Portland cement have an important role in the stabilization and solidification of hazardous chromate ions in hardened cement. AFm monochromate (Ca₄[Al(OH)₆]₂(CrO₄)·12H₂O), [...] Read more.

The calcium aluminate hydrate AFm and AFt phases formed upon hydration of Portland cement have an important role in the stabilization and solidification of hazardous chromate ions in hardened cement. AFm monochromate (Ca₄[Al(OH)₆]₂(CrO₄)·12H₂O), AFm hemichromate (Ca₄[Al(OH)₆]₂(CrO₄)_0.5(OH)·12H₂O) and the chromate-containing AFt phase, Ca₆[Al(OH)₆]₂-(CrO₄)₃·24H₂O, were synthesized and investigated by ¹H, ²⁷Al, and ⁵³Cr MAS NMR spectroscopy. ²⁷Al quadrupolar coupling parameters (C_Q, η_Q) and isotropic chemical shifts (δ_iso) were determined for the three phases, including two distinct Al sites in chromate-AFt, as observed by ²⁷Al MAS and MQMAS NMR. Two dominant peaks are apparent in the ¹H MAS NMR spectra of each of the phases. For the AFm phases, these resonances are assigned to framework hydroxyl groups (1.7–2.0 ppm) and water molecules/hydroxyls (5.0–5.5 ppm) in the interlayer. For chromate-AFt, the peaks are ascribed to framework hydroxyl groups in the [Ca₆Al₂(OH)₁₂]⁶⁺ columns (~1.4 ppm) and water molecules (~4.8 ppm) associated with the Ca ions. ⁵³Cr MAS NMR spectra acquired at 22.3 T for the samples show a narrow resonance for both chromate AFm phases, whereas indications of three distinct Cr resonances are apparent for the chromate AFt. The absence of any second-order quadrupolar effects in the ⁵³Cr NMR spectra strongly suggests that the chromate ions are highly mobile in the anionic sites of the AFm and AFt structures. The NMR data reported in this work are in agreement with the reported crystal structures for the chromate AFm and AFt phases and may be useful for identification and characterization of chromate fixation in cementitious systems, complementing information gained from conventional powder X-ray diffraction studies. Full article

(This article belongs to the Special Issue Cement Related Minerals—in Memory of Herbert Pöllmann)

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24 pages, 5562 KiB

Open AccessArticle

Insights into the Metallogenesis of the Felsic Volcanic Hosted Mundiyawas-Khera Cu Deposit, Alwar Basin, Western India

by Janmejaya Sahoo, Prabodha Ranjan Sahoo, Israil Khan and Akella Satya Venkatesh

Minerals 2022, 12(3), 370; https://doi.org/10.3390/min12030370 - 17 Mar 2022

Cited by 3 | Viewed by 2716

Abstract

Copper and associated gold mineralization in the Mundiyawas-Khera area of western India is hosted by the Proterozoic felsic volcanic rocks of rhyo-dacite composition. Signatures of hydrothermal alteration represented by sericite, epidote, scapolite and carbonates are well observed around the ore mineralization zone. The [...] Read more.

Copper and associated gold mineralization in the Mundiyawas-Khera area of western India is hosted by the Proterozoic felsic volcanic rocks of rhyo-dacite composition. Signatures of hydrothermal alteration represented by sericite, epidote, scapolite and carbonates are well observed around the ore mineralization zone. The felsic volcanic rocks with gently to flat sloping REE pattern, variable negative Eu anomaly, intermediate abundances of HFSE and moderate to low Zr/Y anomalies are suggested to be FII, FIIIa and FIV type rhyolite. The felsic volcanic host rock for copper mineralization has a depleted and flat HREE pattern and indicates the crustal source, which is garnet free. Negative Eu anomaly in the rock is probably because of the intracrustal partial melting formed in a rift related environment. The high temperature magmatic activities are probably evolved due to the partial melting of crust at shallow to moderate depths, suggesting an evolved continental crust. The δ¹³C values of the mineralized carbonate veins range between −10.4‰ and −0.9 ‰ (min = −10.6‰, n = 27), whereas the δ¹⁸O values show a range of 16.35‰ to 25.23‰ (min = 21.49‰, n = 27), ideally suggesting a mixed source for the ore bearing fluid. Geological, geochemical and stable isotope data of the Mundiyawas-Khera copper deposit suggest it to be a VMS/VHMS setup and these insights will lead to finding new deposits in the nearby areas, having same stratigraphic horizons and similar lithogeochemical assemblages. Full article

(This article belongs to the Special Issue Igneous Complex and Mineralization in Subaerial and Submarine Contexts)

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29 pages, 5111 KiB

Open AccessArticle

A Methodology to Assess the Historical Environmental Footprint of In-Situ Recovery (ISR) of Uranium: A Demonstration in the Goliad Sand in the Texas Coastal Plain, USA

by Tanya J. Gallegos, Anne M. Scott, Victoria G. Stengel and Andrew P. Teeple

Minerals 2022, 12(3), 369; https://doi.org/10.3390/min12030369 - 17 Mar 2022

Cited by 4 | Viewed by 2581

Abstract

In-situ recovery (ISR) has been the only technique used to extract uranium from sandstone-hosted uranium deposits in the Pliocene Goliad Sand in the Texas Coastal Plain. Water plays a crucial role throughout the ISR lifecycle of production and groundwater restoration yet neither the [...] Read more.

In-situ recovery (ISR) has been the only technique used to extract uranium from sandstone-hosted uranium deposits in the Pliocene Goliad Sand in the Texas Coastal Plain. Water plays a crucial role throughout the ISR lifecycle of production and groundwater restoration yet neither the water use nor other environmental footprints have been well documented. The goal of this study is to examine historical records for all six ISR operations completed in the Goliad Sand to identify and quantify parameters that indicate the surface and aquifer disturbances, water use, and radon emissions. Overall, the average mine area was 0.00023 ± 0.00006 acres per pound (ac/lb) U₃O₈. The average mine pore volume was 48.9 ± 50 gal/lb U₃O₈ with a minimum affected aquifer volume of 0.51 ± 0.08 cubic feet per pound (cu ft/lb) U₃O_8. An average of 258 ± 40 gallons (gal) of fluid were disposed per pound (lb) U₃O₈, with an average of 169 ± 26 gal/lb U₃O₈ attributed to restoration and 89 ± 36 gal/lb U₃O₈ attributed to the uranium production phase. The average radon emitted was 1.06 × 10⁻³ ± 7.4 × 10⁻⁴ curies per pound (Ci/lb) U₃O₈. Goodness-of-fit (R²) values are ≥0.79 for linear regressions of the amount of uranium produced versus mine area, mine pore volumes, mine aquifer volumes, water pumped, and total water disposed. The R² value for radon emitted was 0.68. However, the water disposed only during the uranium production phase is more strongly correlated to the number of production days (R² = 0.96) than to uranium production (R² = 0.84), whereas the volume of water disposed during restoration is more strongly correlated to the “pore volume” (R² = 0.97) than to uranium production (R² = 0.90). Pore volume is an industry term used to describe the amount of fluid circulated through the aquifer during the uranium production period and stipulated in bond agreements in order to satisfy groundwater restoration requirements. Models constructed in this study can be used to estimate probable water use and the extent of surface and aquifer disturbances associated with ISR-amenable undiscovered uranium resources in the Goliad Sand. The historical perspective offered by the data compiled and correlations may prove useful to both industry and regulators. Full article

(This article belongs to the Special Issue Environmentally Sound In-Situ Recovery Mining of Uranium)

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27 pages, 6154 KiB

Open AccessArticle

Colours of Gemmy Phosphates from the Gavà Neolithic Mines (Catalonia, Spain): Origin and Archaeological Significance

by Yael Díaz-Acha, Marc Campeny, Lluís Casas, Roberta Di Febo, Jordi Ibañez-Insa, Tariq Jawhari, Josep Bosch, Ferran Borrell, Susana Esther Jorge-Villar, Jean-Marc Greneche, Esperança Tauler and Joan Carles Melgarejo

Minerals 2022, 12(3), 368; https://doi.org/10.3390/min12030368 - 17 Mar 2022

Cited by 2 | Viewed by 2606

Abstract

In the Neolithic Gavà mines, variscite and turquoise were exploited for ornaments manufacturing, although some prospective pits and tunnels were dug on other similar greenish minerals such as smectite or kandite. A 3D study of the distribution of mineral phases allows us to [...] Read more.

In the Neolithic Gavà mines, variscite and turquoise were exploited for ornaments manufacturing, although some prospective pits and tunnels were dug on other similar greenish minerals such as smectite or kandite. A 3D study of the distribution of mineral phases allows us to determine the parameters involved in variscite colours. Methods are comprised of quantitative colourimetry, thin section petrography, SEM-BSE-EDS, EMPA, XRD, Raman spectroscopy, and ⁵⁷Fe Mössbauer spectrometry. Mapping of the mines indicates that colour is not directly dependent on depth. Although variscite from Gavà is poor in Cr³⁺ and V⁺³ compared with gemmy variscite from other localities, the deep green samples content has the highest values of Cr³⁺. In the case of cryptocrystalline mixtures with jarosite, phosphosiderite, or goethite, variscite tends to acquire a greenish brown to olivaceous hue. If white minerals such as quartz, kandite, crandallite, or alunite are involved in the mixtures, variscite and turquoise colours become paler. Full article

(This article belongs to the Special Issue Colours in Minerals and Rocks)

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17 pages, 6320 KiB

Open AccessArticle

Mobilization of Au and Ag during Supergene Processes in the Linglong Gold Deposit: Evidence from SEM and LA–ICP–MS Analyses of Sulfides

by Hong Wang, Tingguang Lan, Yinghua Chen, Huanlong Hu and Lei Shu

Minerals 2022, 12(3), 367; https://doi.org/10.3390/min12030367 - 16 Mar 2022

Cited by 3 | Viewed by 2858

Abstract

Precious metals can be mobilized during supergene processes, which are important for the formation of high-grade or high-purity ores. The world-class Linglong gold deposit has high-grade ores that have undergone supergene processes in the near-surface zone. Under which conditions the supergene modification occurred [...] Read more.

Precious metals can be mobilized during supergene processes, which are important for the formation of high-grade or high-purity ores. The world-class Linglong gold deposit has high-grade ores that have undergone supergene processes in the near-surface zone. Under which conditions the supergene modification occurred and how Au and Ag behaved during the supergene processes have been poorly studied in this deposit. Here, we performed scanning electron microscope (SEM) and laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) analyses on samples from the supergene enrichment zone of the Linglong gold deposit. The results show that secondary minerals were formed sequentially from magnetite-goethite-limonite to marcasite-acanthite, and finally to siderite after the primary minerals of pyrite-pyrrhotite-chalcopyrite. These mineral assemblages and variations indicate that the supergene modification by groundwater occurred under oxidative and weakly acidic conditions in the near-surface zone and evolved to reductive and near neutral conditions in the supergene enrichment zone. The newly formed marcasite has much higher Au (0.003–23.5 ppm, mean of 1.33 ppm) and Ag (81.7–6021 ppm, mean of 1111 ppm) concentrations than those of the primary pyrite (Au of 0.004–0.029 ppm and Ag of 0.22–4.14 ppm), which together with the formation of independent Ag–S mineral (acanthite), indicates that Au and Ag were significantly mobilized and fractionated during the supergene processes. These processes improved the Au and Ag grades in the supergene enrichment zone and thus facilitate their extraction. Full article

(This article belongs to the Section Mineral Deposits)

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17 pages, 2327 KiB

Open AccessArticle

The Diverse Indigenous Bacterial Community in the Rudna Mine Does Not Cause Dissolution of Copper from Kupferschiefer in Oxic Conditions

by Malin Bomberg, Hanna Miettinen and Päivi Kinnunen

Minerals 2022, 12(3), 366; https://doi.org/10.3390/min12030366 - 16 Mar 2022

Cited by 3 | Viewed by 1642

Abstract

Blasting and fracking of rock in mines exposes fresh rock surfaces to the local water and microbial communities. This may lead to leaching of metals from the rock by chemical or biological means and can cause acidification of the water system in the [...] Read more.

Blasting and fracking of rock in mines exposes fresh rock surfaces to the local water and microbial communities. This may lead to leaching of metals from the rock by chemical or biological means and can cause acidification of the water system in the mine, i.e., acid rock drainage (ARD). Failure to prevent leakage of metal contaminated mine water may be harmful for the environment, especially to the local groundwater. In the Rudna mine, Poland, an in situ bioleaching pilot test at approximately 1 km depth was performed in the H2020 BIOMOre project (Grant Agreement #642456). After the leaching stage, different methods for irreversible inhibition of acidophilic iron oxidizing microorganisms used for reoxidation of reduced iron in the leaching solution were tested and were shown to be effective. However, the potential of the natural mine water microbial communities to cause leaching of copper or acidification of the mine waters has not been tested. In this study, we set up a microcosm experiment simulating the exposure of freshly fractionated Kupferschiefer sandstone or black schist to two different chloride-rich water types in the Rudna mine. The pH of the microcosms water was measured over time. At the end of an 18-week incubation, the bacterial community was examined by high throughput sequencing and qPCR, and the presence of copper tolerant heterotrophic bacteria was tested by cultivation. The dissolution of copper into the chloride rich microcosm water was measured. The pH in the microcosms did not decrease over the time of incubation. The sandstone increased the number of bacteria in the microcosms with one or over two orders of magnitude compared to the original water. The bacterial communities in the two tested mine waters were diverse and similar despite the difference in salinity. The bacterial diversity was high but changed in the less saline water during the incubation. There was a high content of sulphate reducing bacteria in the original mine waters and in the microcosms, and their number increased during the incubation. No acidophilic iron oxidizers were detected, but in the microcosms containing the less saline water low numbers of Cu tolerant bacteria were detected. Copper to a concentration of up to 939 mg L⁻¹ was leached from the rock also in the microbe-free negative controls, which was up to 2.4 times that leached in the biotic microcosms, indicating that the leaching was also abiotic, not only caused by bacteria. Full article

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

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13 pages, 6761 KiB

Open AccessArticle

Study on the Activity of Metakaolin Produced by Traditional Rotary Kiln in China

by Rongchuan Cao, Zheng Fang, Man Jin and Yu Shang

Minerals 2022, 12(3), 365; https://doi.org/10.3390/min12030365 - 16 Mar 2022

Cited by 6 | Viewed by 2437

Abstract

This paper analyzed the activity of coal-based metakaolin and non-coal-based metakaolin (ordinary metakaolin) commonly used in the Chinese market. The content of kaolin was detected by XPF. The phases of kaolin, metakaolin and corresponding alkali-excited reactants were detected by XRD. The contents of [...] Read more.

This paper analyzed the activity of coal-based metakaolin and non-coal-based metakaolin (ordinary metakaolin) commonly used in the Chinese market. The content of kaolin was detected by XPF. The phases of kaolin, metakaolin and corresponding alkali-excited reactants were detected by XRD. The contents of Al (IV), Al (V) and Al (VI) in kaolin and metakaolin were analyzed by ²⁷Al NMR. The micromorphology of kaolin and metakaolin were observed by SEM. The water-resistance of alkali-activated metakaolin was tested by immersion experiment. The results showed that a lot of corundum and quartz were present in the coal-based metakaolin, which was caused by over calcination. Furthermore, large amounts of sillimanite, quartz and cristobalite existed in ordinary metakaolin with a low content of amorphous aluminum silicate, which was caused by excessive impurities in the raw materials and over calcination. These crystalline substances could not react in an alkali solution, and their existence reduced the activity of the two metakaolins. Both of the two metakaolin production methods need to be improved to increase the activity. Full article

(This article belongs to the Topic Industrial Application of Clays and Clay Minerals)

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15 pages, 4260 KiB

Open AccessArticle

Facile Preparation of Organo-Modified ZnO/Attapulgite Nanocomposites Loaded with Monoammonium Glycyrrhizinate via Mechanical Milling and Their Synergistic Antibacterial Effect

by Fangfang Yang, Yameng Song, Aiping Hui, Yuru Kang, Yanmin Zhou and Aiqin Wang

Minerals 2022, 12(3), 364; https://doi.org/10.3390/min12030364 - 16 Mar 2022

Cited by 4 | Viewed by 2263

Abstract

In this study, monoammonium glycyrrhizinate (MAG) was introduced into cetyltrimethyl ammonium bromide (CTAB)-modified ZnO/attapulgite (APT) via a mechanical process to form performance-enhanced antibacterial nanocomposites (MAG/C–ZnO/APT). The APT supported ZnO nanocomposite (ZnO/APT) was prepared by a conventional precipitation method, and 20–50 nm of globular [...] Read more.

In this study, monoammonium glycyrrhizinate (MAG) was introduced into cetyltrimethyl ammonium bromide (CTAB)-modified ZnO/attapulgite (APT) via a mechanical process to form performance-enhanced antibacterial nanocomposites (MAG/C–ZnO/APT). The APT supported ZnO nanocomposite (ZnO/APT) was prepared by a conventional precipitation method, and 20–50 nm of globular ZnO nanoparticles were uniformly decorated on APT nanorods. The FTIR and zeta potential analyses demonstrated that modification by CTAB facilitated the loading of MAG into ZnO/APT by H-bonding and electrostatic interactions. Antibacterial evaluation results indicate that MAG/C–ZnO/APT nanocomposites with CTAB and MAG doses of 2.5% and 0.25%, respectively, exhibited synergistically enhanced inhibitory activities against Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamases Escherichia coli, with minimum inhibitory concentrations of 1, 0.1, 0.25, 5, 0.1, and 2.5 mg/mL, respectively, which are better than those of ZnO/APT, C–ZnO/APT and MAG. Moreover, the nanocomposites had low cytotoxicity on human normal cell line L-O2. Therefore, this study provided a more effective strategy to extend the antibacterial spectrum and strengthen the inhibitory effects of antibiotic-free materials to address increasingly serious situations of microbial infection. Full article

(This article belongs to the Special Issue Nanotubular and Nanofibrous Clay Minerals)

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26 pages, 41297 KiB

Open AccessArticle

Three-Dimensional Structural Modeling (3D SM) and Joint Geophysical Characterization (JGC) of Hydrocarbon Reservoir

by Baoyi Zhang, Yongqiang Tong, Jiangfeng Du, Shafqat Hussain, Zhengwen Jiang, Shahzad Ali, Ikram Ali, Majid Khan and Umair Khan

Minerals 2022, 12(3), 363; https://doi.org/10.3390/min12030363 - 16 Mar 2022

Cited by 13 | Viewed by 3167

Abstract

A complex structural geology generally leads to significant consequences for hydrocarbon reservoir exploration. Despite many existing wells in the Kadanwari field, Middle Indus Basin (MIB), Pakistan, the depositional environment of the early Cretaceous stratigraphic sequence is still poorly understood, and this has implications [...] Read more.

A complex structural geology generally leads to significant consequences for hydrocarbon reservoir exploration. Despite many existing wells in the Kadanwari field, Middle Indus Basin (MIB), Pakistan, the depositional environment of the early Cretaceous stratigraphic sequence is still poorly understood, and this has implications for regional geology as well as economic significance. To improve our understanding of the depositional environment of complex heterogeneous reservoirs and their associated 3D stratigraphic architecture, the spatial distribution of facies and properties, and the hydrocarbon prospects, a new methodology of three-dimensional structural modeling (3D SM) and joint geophysical characterization (JGC) is introduced in this research using 3D seismic and well logs data. 3D SM reveals that the field in question experienced multiple stages of complex deformation dominated by an NW to SW normal fault system, high relief horsts, and half-graben and graben structures. Moreover, 3D SM and fault system models (FSMs) show that the middle part of the sequence underwent greater deformation compared to the areas surrounding the major faults, with predominant one oriented S30°–45° E and N25°–35° W; with the azimuth at 148°–170° and 318°–345°; and with the minimum (28°), mean (62°), and maximum (90°) dip angles. The applied variance edge attribute better portrays the inconsistencies in the seismic data associated with faulting, validating seismic interpretation. The high amplitude and loss of frequency anomalies of the sweetness and root mean square (RMS) attributes indicate gas-saturated sand. In contrast, the relatively low-amplitude and high-frequency anomalies indicate sandy shale, shale, and pro-delta facies. The petrophysical modeling results show that the E sand interval exhibits high effective porosity (∅_eff) and hydrocarbon saturation (S_hc) compared to the G sand interval. The average petrophysical properties we identified, such as volume of shale (V_shale), average porosity (∅_avg), ∅_eff, water saturation (S_W), and the S_hc of the E sand interval, were 30.5%, 17.4%, 12.2%, 33.2% and, 70.01%, respectively. The findings of this study can help better understand the reservoir’s structural and stratigraphic characteristics, the spatial distribution of associated facies, and petrophysical properties for reliable reservoir characterization. Full article

(This article belongs to the Special Issue 3D/4D Geological Modeling for Mineral Exploration)

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12 pages, 9884 KiB

Open AccessArticle

Removal of Aqueous Cu²⁺ by Amorphous Calcium Carbonate: Efficiency and Mechanism

by Zisheng Liao, Shijun Wu, Hanxiao Zhang and Fanrong Chen

Minerals 2022, 12(3), 362; https://doi.org/10.3390/min12030362 - 16 Mar 2022

Cited by 5 | Viewed by 1983

Abstract

Crystalline calcium carbonate (CaCO₃, such as calcite) could scavenge aqueous metals via adsorption and coprecipitation. As a precursor to crystalline CaCO₃, amorphous calcium carbonate (ACC) is poorly understood on metals removal. Herein, we synthesized silica-stabilized ACC and investigated its [...] Read more.

Crystalline calcium carbonate (CaCO₃, such as calcite) could scavenge aqueous metals via adsorption and coprecipitation. As a precursor to crystalline CaCO₃, amorphous calcium carbonate (ACC) is poorly understood on metals removal. Herein, we synthesized silica-stabilized ACC and investigated its Cu²⁺ removal efficiency and mechanism. The results showed that the Cu²⁺ removal efficiency by ACC is controlled by the initial solution pH, initial Cu²⁺ concentration, contacting time, and ACC dosage. The maximum Cu²⁺ removal capacity was 543.4 mg/g at an ACC dosage of 1 g/L, an initial pH of 5.0, an initial Cu²⁺ concentration of 1000 mg/L, and an equilibrium time of 20 h. X-ray powder diffraction (XRD) and scanning electron microscope with an energy dispersive spectrometer (SEM-EDS) revealed that Cu²⁺ precipitated as paratacamite (Cu₂(OH)₃Cl, space group: R

\bar{3}

) at an ACC dosage of 1 g/L, whereas botallackite (Cu₂(OH)₃Cl, space group: P2₁/m) was the Cu-bearing product for crystalline calcite using the same dosage as ACC. However, Cu²⁺ preferred to incorporate into calcite, which is transformed from ACC at high ACC loading (such as 4 g/L). Our results demonstrated that the crystallinity and dosage of CaCO₃ could control the Cu²⁺ removal mechanism. Full article

(This article belongs to the Section Clays and Engineered Mineral Materials)

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14 pages, 3921 KiB

Open AccessArticle

Recovery of Platinum Group Metals from Leach Solutions of Spent Catalytic Converters Using Custom-Made Resins

by Pulleng Moleko-Boyce, Hlamulo Makelane, Mbokazi Z. Ngayeka and Zenixole R. Tshentu

Minerals 2022, 12(3), 361; https://doi.org/10.3390/min12030361 - 16 Mar 2022

Cited by 9 | Viewed by 4065

Abstract

Platinum group metals (PGMs) play a key role in modern society as they find application in clean technologies and other high-tech equipment. Spent catalytic converters as a secondary resource contain higher PGM concentrations and the recovery of these metals via leaching is continuously [...] Read more.

Platinum group metals (PGMs) play a key role in modern society as they find application in clean technologies and other high-tech equipment. Spent catalytic converters as a secondary resource contain higher PGM concentrations and the recovery of these metals via leaching is continuously being improved but efforts are also directed at the purification of individual metal ions. The study presents the recovery of PGMs, namely, rhodium (Rh), platinum (Pt) and palladium (Pd) as well as base metals, namely, zinc (Zn), nickel (Ni), iron (Fe), manganese (Mn) and chromium (Cr) using leachates from spent diesel and petrol catalytic converters. The largest amount of Pt was leached from the diesel catalytic converter while the petrol gave the highest amount of Pd when leached with aqua regia. Merrifield beads (M) were functionalized with triethylenetetramine (TETA), ethane-1,2-dithiol (SS) and bis((1H-benzimidazol-2-yl)methyl)sulfide (NSN) to form M-TETA, M-SS and M-NSN, respectively, for recovery of PGMs and base metals from the leach solutions. The adsorption and loading capacities of the PGMs and base metals were investigated using column studies at 1 M HCl concentration. The loading capacity was observed in the increasing order of Pd to be 64.93 mmol/g (M-SS), 177.07 mmol/g (M-NSN), and 192.0 mmol/g (M-TETA), respectively, from a petrol catalytic converter. The M-NSN beads also had a much higher loading capacity for Fe (489.55 mmol/g) compared to other base metals. The finding showed that functionalized Merrifield resins were effective for the simultaneous recovery of PGMs and base metals from spent catalytic converters. Full article

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

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17 pages, 3475 KiB

Open AccessArticle

An Integrated Capture of Red Mud and One-Step Heat-Treatment Process to Recover Platinum Group Metals and Prepare Glass-Ceramics from Spent Auto-Catalysts

by Chuan Liu, Shuchen Sun, Ganfeng Tu and Faxin Xiao

Minerals 2022, 12(3), 360; https://doi.org/10.3390/min12030360 - 15 Mar 2022

Cited by 4 | Viewed by 1982

Abstract

Co-treatment for two kinds of hazardous solid waste is an effective method to reduce cost and increase recycle efficiency of value resource. This work developed an integrated process based on capture of red mud (RM) and a one-step heat-treatment process to efficiently recover [...] Read more.

Co-treatment for two kinds of hazardous solid waste is an effective method to reduce cost and increase recycle efficiency of value resource. This work developed an integrated process based on capture of red mud (RM) and a one-step heat-treatment process to efficiently recover PGMs from spent auto-catalysts (SAC) and reuse RM simultaneously. Firstly, the iron oxide in RM was reduced to metallic iron to capture PGMs by the reduction process, without the addition of an extra reducing agent, since SAC contained abundant organic volatiles. Then, the mixed waste of SAC and RM was melted under high temperature with additives of CaO and H₃BO₃. More than 99% of PGMs can be extracted under the optimal conditions of 40–50 wt% of RM addition, 14 wt% of H₃BO₃ addition, 0.7–0.8 of basicity, 1500 °C of temperature, and 40 min of holding time. In addition, PGM content in obtained glassy slag was less than 1 g/t. The mechanism of iron trapping PGMs was also discussed in detailed, which mainly contained two stages: migration of PGMs and separation of PGM-bearing alloy and slag phases. Besides, the obtained glassy slag was further prepared into glass-ceramic by a one-step heat-treatment process. It was found that the prepared glass-ceramic has good thermostability and an excellent stabilizing effect on heavy metals. Overall, the results indicated that the developed integrated smelting–collection process is an efficient and promising method for the reutilization of SAC and RM. Full article

(This article belongs to the Topic Recycling and Value-Added Utilization of Secondary Raw Materials)

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Minerals, Volume 12, Issue 3 (March 2022) – 114 articles

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