Minerals

21 pages, 12047 KiB

Open AccessArticle

Tailings Behavior Assessment Using Piezocone Penetration Test

by Magdalena Wróżyńska

Minerals 2024, 14(2), 208; https://doi.org/10.3390/min14020208 - 18 Feb 2024

Viewed by 902

Intensive economic development is associated with an increasing demand for raw materials, including minerals. An illustrative example of this issue is the development of the copper industry. A significant problem arising from the scale of copper production is the management of an ever-growing [...] Read more.

Intensive economic development is associated with an increasing demand for raw materials, including minerals. An illustrative example of this issue is the development of the copper industry. A significant problem arising from the scale of copper production is the management of an ever-growing amount of post-flotation tailings. This necessitates the need to ensure the continuity of safe storage. This study presents the results of studies on the behavior of deposits in the Żelazny Most Tailings Storage Facility (Poland). The primary objective of this study was to estimate the settlements of tailings under variable deposition conditions. The results were assessed using two methods: indirect and direct; this was based on cone penetration test (CPTU) results. The results were verified using Modified Cam Clay (MCC) modeling. Depending on the type of test, settlements ranged from several dozen centimeters to over three meters. Despite the observed differences, the results of both CPTU methods indicate a convergent trend in tailings behavior. Conversely, the results estimated using the direct method and numerical modeling demonstrate a high level of agreement. Full article

(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)

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17 pages, 2869 KiB

Open AccessArticle

An Efficient Peptide Screening Method for Mineral-Binding Peptides

by Lam Ian Ku, Liza Forbes and Susana Brito e Abreu

Minerals 2024, 14(2), 207; https://doi.org/10.3390/min14020207 - 17 Feb 2024

Viewed by 939

Abstract

In mineral processing, arsenic-bearing minerals are particularly difficult to separate from their non-arsenic counterparts because they possess similar surface properties. Peptides are well known for their target specificity and can offer a ‘green’ alternative to traditional flotation reagents. However, the use of peptide [...] Read more.

In mineral processing, arsenic-bearing minerals are particularly difficult to separate from their non-arsenic counterparts because they possess similar surface properties. Peptides are well known for their target specificity and can offer a ‘green’ alternative to traditional flotation reagents. However, the use of peptide technologies in mineral processing for developing novel flotation reagents has not been explored. Hence, this work aims to develop a screening method to identify mineral-binding peptides as potential reagent candidates. It is hypothesised that peptides can selectively adsorb onto mineral surfaces, and this method can efficiently identify mineral-binding peptides with high specificity toward the target minerals. The methodology presented involves a selection of peptide candidates from existing literature that show affinity toward arsenic species. These peptides were tested for their adsorption performance onto selected mineral surfaces to evaluate their mineral selectivity under flotation conditions. The study demonstrates that the screening method developed is effective in identifying peptides that have an affinity for target minerals, in this case, arsenic minerals. The screening method can be applied to other minerals, thus, unlocking the potential for developing new reagent chemistries for use in mineral processing. Full article

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

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20 pages, 12923 KiB

Open AccessArticle

Enrichment Factors and Metallogenic Models of Critical Metals in Late Permian Coal Measures from Yunnan, Guizhou, and Guangxi Provinces

by Bo Cao, Xuehai Fu, Junqiang Kang, Pan Tang and Hui Xu

Minerals 2024, 14(2), 206; https://doi.org/10.3390/min14020206 - 17 Feb 2024

Viewed by 685

Abstract

The Late Permian coal measures in eastern Yunnan, western Guizhou, and central Guangxi are significantly enriched in critical metals that could serve as important supplements to conventional critical metal deposits in China. This study collected previous geochronological and geochemical data from the Late [...] Read more.

The Late Permian coal measures in eastern Yunnan, western Guizhou, and central Guangxi are significantly enriched in critical metals that could serve as important supplements to conventional critical metal deposits in China. This study collected previous geochronological and geochemical data from the Late Permian coal measures to evaluate the distribution characteristics and enrichment factors of critical metals. Moreover, metallogenic models for critical metals were also developed. The results showed that Late Permian coal measures in Yunnan, Guizhou, and Guangxi provinces exhibited abnormal enrichment in Nb, Zr, and rare earth elements (REY, or REE if Y is excluded). The Emeishan mafic rocks and intermediate-felsic volcanic ash from the Truong Son orogenic belt underwent chemical weathering, with Nb and Zr selectively preserved in situ in the form of heavy minerals (e.g., rutile, zircon, and anatase), which subsequently led to the enrichment of Nb and Zr in bauxite and Al-claystone at the bottom of the Late Permian coal measures. Intermediate-felsic volcanic ash from the Emeishan large igneous province (ELIP) and the Truong Son orogenic belt supplied Nb, Zr, and REY for the middle and upper parts of the Late Permian coal measures. The intermediate-felsic mineral material of the coal measures in the intermediate zone, outer zone, and outside zone of ELIP are derived mainly from the ELIP, the mixture from ELIP and the Truong Son orogenic belt, and the Truong Son orogenic belts, respectively. Nb, Zr, and REY were leached by acidic aqueous solutions and from the parting and roof into underlying coal seams, where they deposited as authigenic minerals or adsorbed ions on organic matter during early coalification. Full article

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20 pages, 14650 KiB

Open AccessArticle

Fractal Evolution Characteristics of Isolation Layers in a Submarine Gold Mine: A Case Study

by Yin Chen, Zijun Li, Weixing Lin, Yan He, Guoqiang Wang, Renze Ou and Qi Liu

Minerals 2024, 14(2), 205; https://doi.org/10.3390/min14020205 - 17 Feb 2024

Viewed by 565

Abstract

The establishment of an isolation layer in submarine mining has been a persistent challenge. In the context of this research, we conducted a similarity simulation test to preliminarily assess the interaction between the thickness and extent of the isolation layer. Subsequently, we introduce [...] Read more.

The establishment of an isolation layer in submarine mining has been a persistent challenge. In the context of this research, we conducted a similarity simulation test to preliminarily assess the interaction between the thickness and extent of the isolation layer. Subsequently, we introduce an innovative approach that integrates fractal theory and the Bonded Block Model (BBM) to simulate undersea isolation layer mining. The validation of this method relies on on-site borehole scanning and displacement monitoring, which depict the intricate fractal evolution of fractures and predict the optimal thickness of the isolation layer. Our findings affirm the robustness and validity of this method. Evaluation of the fractal dimensions of fractures reveals that a critical threshold of 1.7 is essential to prevent structural failure of the isolation layer, while a limit of 1.5 is necessary to avoid significant water ingress. Remarkably, the correlation dimension of the settlement time series closely aligns with the fractal dimension of the fractures, underscoring the feasibility of ensuring the safety of isolation layer mining through real-time settlement monitoring. Full article

(This article belongs to the Topic New Advances in Mining Technology)

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14 pages, 2318 KiB

Open AccessArticle

The Raw Material Challenge of Creating a Green Economy

by Richard Jeremy Herrington

Minerals 2024, 14(2), 204; https://doi.org/10.3390/min14020204 - 17 Feb 2024

Viewed by 1291

Abstract

Clean technologies and infrastructure for our low-carbon, green future carry intense mineral demands. The ambition remains to recycle and reuse as much as we can; however, newly mined resources will be required in the near term despite the massive improvements in the reuse [...] Read more.

Clean technologies and infrastructure for our low-carbon, green future carry intense mineral demands. The ambition remains to recycle and reuse as much as we can; however, newly mined resources will be required in the near term despite the massive improvements in the reuse and recycling of existing end-of-use products and wastes. Growth trends suggest that mining will still play a role after 2050 since the demand for metals will increase as the developing world moves toward a per capita usage of materials comparable to that of the developed world. There are sufficient geological resources to deliver the required mineral commodities, but the need to mine must be balanced with the requirement to tackle environmental and social governance issues and to deliver sustainable development goals, ensuring that outcomes are beneficial for both the people and planet. Currently, the lead time to develop new mines following discovery is around 16 years, and this needs to be reduced. New approaches to designing and evaluating mining projects embracing social, biodiversity, and life cycle analysis aspects are pivotal. New frontiers for supply should include neglected mined wastes with recoverable components and unconventional new deposits. New processing technologies that involve less invasive, lower energy and cleaner methodologies need to be explored, and developing such methodologies will benefit from using nature-based solutions like bioprocessing for both mineral recovery and for developing sustainable landscapes post mining. Part of the new ambition would be to seek opportunities for more regulated mining areas in our own backyard, thinking particularly of old mineral districts of Europe, rather than relying on sources with potentially and less controllable, fragile, and problematic supply chains. The current debate about the potential of mining our deep ocean, as an alternative to terrestrial sources needs to be resolved and based on a broader analysis; we can then make balanced societal choices about the metal and mineral supply from the different sources that will be able to deliver the green economy while providing a net-positive deal for the planet and its people. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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19 pages, 14121 KiB

Open AccessArticle

Chemically Oscillating Reactions as a New Model for the Formation of Mineral Patterns in Agate Geodes and Concretions

by Dominic Papineau

Minerals 2024, 14(2), 203; https://doi.org/10.3390/min14020203 - 16 Feb 2024

Viewed by 849

Abstract

Agate geodes contain spheroidal patterns characterized by spectacularly coloured and circularly concentric laminations with radially aligned quartz crystals, yet the origin of these geometric patterns has remained enigmatic. Here, detailed comparisons are documented between these kinds of patterns in a selection of geodes [...] Read more.

Agate geodes contain spheroidal patterns characterized by spectacularly coloured and circularly concentric laminations with radially aligned quartz crystals, yet the origin of these geometric patterns has remained enigmatic. Here, detailed comparisons are documented between these kinds of patterns in a selection of geodes and concretions and those produced by abiotic chemically oscillating reactions. We find strikingly comparable self-similar, fractal patterns in both natural volcanogenic geodes and sedimentary concretions as well as in these benchtop experiments. In addition, the mineralogical composition of patterns and associated organic matter point to the oxidation of organic compounds in both geodes and concretions. This process occurred during diagenetic or supergene alteration, and it is consistent with spontaneous and abiotic chemically oscillating reactions. It is concluded that the oxidation of organic acids was involved in the formation of these patterns and that these rocks indicate oxidation–reduction reactions involving organic carbon, which itself may be abiotic or biological in origin. Hence, agate geodes and concretions represent the abiotic biosignatures of possible biological origin in volcanic and sedimentary rocks. Full article

(This article belongs to the Special Issue Mineralogy, Geochemistry, and Origin of Agate: An Ongoing Challenge)

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29 pages, 5274 KiB

Open AccessArticle

Machine Learning-Based Lithological Mapping from ASTER Remote-Sensing Imagery

by Hazhir Bahrami, Pouya Esmaeili, Saeid Homayouni, Amin Beiranvand Pour, Karem Chokmani and Abbas Bahroudi

Minerals 2024, 14(2), 202; https://doi.org/10.3390/min14020202 - 16 Feb 2024

Viewed by 941

Abstract

Accurately mapping lithological features is essential for geological surveys and the exploration of mineral resources. Remote-sensing images have been widely used to extract information about mineralized alteration zones due to their cost-effectiveness and potential for being widely applied. Automated methods, such as machine-learning [...] Read more.

Accurately mapping lithological features is essential for geological surveys and the exploration of mineral resources. Remote-sensing images have been widely used to extract information about mineralized alteration zones due to their cost-effectiveness and potential for being widely applied. Automated methods, such as machine-learning algorithms, for lithological mapping using satellite imagery have also received attention. This study aims to map lithologies and minerals indirectly through machine-learning algorithms using advanced spaceborne thermal emission and reflection radiometer (ASTER) remote-sensing data. The capabilities of several machine-learning (ML) algorithms were evaluated for lithological mapping, including random forest (RF), support vector machine (SVM), gradient boosting (GB), extreme gradient boosting (XGB), and a deep-learning artificial neural network (ANN). These methods were applied to ASTER imagery of the Sar-Cheshmeh copper mining region of Kerman Province, in southern Iran. First, several spectral features that were extracted from ASTER bands were used as input data. Second, correlation coefficients between the original spectral bands and features were extracted. The importance of the random forest features (RF’s feature importance) was subsequently computed, and features with less importance were removed. Finally, the remained features were given to the models as input data in the second scenario. Accuracy assessments were performed for lithological classes in the study region, including Sar-Cheshmeh porphyry, quartz eye, late fine porphyry, hornblende dike, granodiorite, feldspar dike, biotite dike, andesite, and alluvium. The overall accuracy results of lithological mapping showed that ML-based algorithms without feature extraction have the highest accuracy. The overall accuracy percentages for ML-based algorithms without conducting feature extraction were 84%, 85%, 80%, 82%, and 80% for RF, SVM, GB, XGB, and ANN, respectively. The results of this study would be of great interest to geologists for lithological mapping and mineral exploration, particularly for selecting appropriate ML-based techniques to be implemented in similar regions. Full article

(This article belongs to the Special Issue Geological, Structural, Geochemical, Hyperspectral, and Geostatistical Modeling for Mineral Exploration)

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23 pages, 3233 KiB

Open AccessReview

Porphyrin-Based Molecules in the Fossil Record Shed Light on the Evolution of Life

by Juan D. Ayala, Elena R. Schroeter and Mary H. Schweitzer

Minerals 2024, 14(2), 201; https://doi.org/10.3390/min14020201 - 16 Feb 2024

Viewed by 1032

Abstract

The fossil record demonstrates the preservation of porphyrins (e.g., heme) in organic sediments and the fossilized remains of animals. These molecules are essential components in modern metabolic processes, such as electron transport (cytochromes) and oxygen transport (hemoglobin), and likely originated before the emergence [...] Read more.

The fossil record demonstrates the preservation of porphyrins (e.g., heme) in organic sediments and the fossilized remains of animals. These molecules are essential components in modern metabolic processes, such as electron transport (cytochromes) and oxygen transport (hemoglobin), and likely originated before the emergence of life. The integration and adaptation of porphyrins and structurally similar molecules (e.g., chlorophylls) are key aspects in the evolution of energy production (i.e., aerobic respiration and photosynthesis) and complex life (i.e., eukaryotes and multicellularity). Here, we discuss the evolution and functional diversity of heme-bound hemoglobin proteins in vertebrates, along with the preservation of these molecules in the fossil record. By elucidating the pivotal role of these molecules in the evolution of life, this review lays the groundwork necessary to explore hemoglobin as a means to investigate the paleobiology of extinct taxa, including non-avian dinosaurs. Full article

(This article belongs to the Special Issue Recent Advances in Bone Diagenesis)

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21 pages, 15627 KiB

Open AccessArticle

Discovery of Pseudomorph Scapolite and Diagenetic Indication from the Permian Volcaniclastic Rocks in Western Sichuan (SW China)

by Xiaohong Liu, Yue’e Li, Cong Tan, Zhenglin Cao, Hui Jin, Mingyou Feng, Maolong Xia and Junlang Chen

Minerals 2024, 14(2), 200; https://doi.org/10.3390/min14020200 - 15 Feb 2024

Viewed by 753

Abstract

Volcaniclastic rocks are important unconventional oil and gas reservoirs from which it is difficult to determine the protolith due to strong metasomatic alteration. Intensive alteration has occurred in much of western China, but few robustly documented examples are known from which to assess [...] Read more.

Volcaniclastic rocks are important unconventional oil and gas reservoirs from which it is difficult to determine the protolith due to strong metasomatic alteration. Intensive alteration has occurred in much of western China, but few robustly documented examples are known from which to assess the alteration processes. Further recognition from the petrological and mineralogical record is essential to quantify the diagenetic environment, the degree of alteration, and its impacts. Permian volcanic rocks are widely developed in the western Sichuan Basin (southwestern China), with a thickness of more than 200 m. The thickness of volcaniclastic rocks in the Permian Emeishan Basalt Formation is up to 140 m, with a 5600~6000 m burial depth. In this study, we demonstrate an approach to recognizing hydrothermal alteration by the occurrence of scapolite megacryst mineral pseudomorphs (SMMPs) in Permian volcaniclastic rocks in the Sichuan Basin (southwestern China). The results show that SMMPs in the Permian volcaniclastic rocks in the western Sichuan Basin mainly occur in the lower part of the Permian basalts as intragranular minerals and rock inclusions. Scapolite is transformed into quartz and albite, and only the pseudomorph is preserved, indicating secondary hydrothermal fluid metasomatic alteration. Scapolite is formed after microcrystalline titanite and is the product of the high-temperature pneumatolytic metasomatism of plagioclase from the mafic protolith during the post-magmatic stage. The mixing of meteoric water and barium-rich hydrothermal fluid leads to the precipitation of barite; additionally, the pores are filled with barite and halite after the alteration of scapolite. The silicification and hydrothermal dissolution of scapolite and the albitization of sodium-rich matrix minerals increase the pore volume, which is conducive to the later recharge by hydrothermal fluids. The discovery of SMMPs can serve as an indicator of the high-temperature pneumatolytic metasomatism and mixing of meteoric water and deep hydrothermal fluid. Full article

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

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20 pages, 15919 KiB

Open AccessFeature PaperArticle

The Temporal Distribution of the Host Rocks to Gold, the Archean Witwatersrand Basin, South Africa

by Neil Phillips, Julian Vearncombe, Dave Craw and Arthur Day

Minerals 2024, 14(2), 199; https://doi.org/10.3390/min14020199 - 15 Feb 2024

Viewed by 1158

Abstract

The hosts to gold around the Witwatersrand Basin span over 400 my, through 14 km of stratigraphy in a variety of host rocks and in tectonic settings that include periods of rifting, thermal subsidence, foreland basin, flood basalt outpouring, graben development, and further [...] Read more.

The hosts to gold around the Witwatersrand Basin span over 400 my, through 14 km of stratigraphy in a variety of host rocks and in tectonic settings that include periods of rifting, thermal subsidence, foreland basin, flood basalt outpouring, graben development, and further thermal subsidence. A geological model that assumes placer processes to explain this diversity implies a super-long-lived and special source of the detrital gold, transport, and highly effective sorting processes over a time span of 400 my. There is no evidence of a special source and sorting over such a long time period. In the Phanerozoic, this would be equivalent to the special source and sorting processes operating continually over an equivalent period of geological time spanning from the Devonian up until the present day; this is as yet recognised nowhere else on the planet. With regard to the geological model that assumes a placer process, this is untenable because of these scientific shortcomings and its lack of success in exploration. A better use of funds may be to consider alternative approaches and epigenetic models in exploration. Full article

(This article belongs to the Special Issue Geological, Structural, Geochemical, Hyperspectral, and Geostatistical Modeling for Mineral Exploration)

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Graphical abstract

28 pages, 7482 KiB

Open AccessFeature PaperArticle

Coupled Microstructural EBSD and LA-ICP-MS Trace Element Mapping of Pyrite Constrains the Deformation History of Breccia-Hosted IOCG Ore Systems

by Samuel Anthony King, Nigel John Cook, Cristiana Liana Ciobanu, Kathy Ehrig, Yuri Tatiana Campo Rodriguez, Animesh Basak and Sarah Gilbert

Minerals 2024, 14(2), 198; https://doi.org/10.3390/min14020198 - 15 Feb 2024

Viewed by 1100

Abstract

Electron backscatter diffraction (EBSD) methods are used to investigate the presence of microstructures in pyrite from the giant breccia-hosted Olympic Dam iron–oxide copper gold (IOCG) deposit, South Australia. Results include the first evidence for ductile deformation in pyrite from a brecciated deposit. Two [...] Read more.

Electron backscatter diffraction (EBSD) methods are used to investigate the presence of microstructures in pyrite from the giant breccia-hosted Olympic Dam iron–oxide copper gold (IOCG) deposit, South Australia. Results include the first evidence for ductile deformation in pyrite from a brecciated deposit. Two stages of ductile behavior are observed, although extensive replacement and recrystallization driven by coupled dissolution–reprecipitation reaction have prevented widespread preservation of the earlier event. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) element maps of pyrite confirm that many pyrite grains display compositional zoning with respect to As, Co, and Ni, but that the zoning is often irregular, patchy, or otherwise disrupted and are readily correlated with observed microstructures. The formation of ductile microstructures in pyrite requires temperatures above ~260 °C, which could potentially be related to heat from radioactive decay and fault displacements during tectonothermal events. Coupling EBSD methods with LA-ICP-MS element mapping allows a comprehensive characterization of pyrite textures and microstructures that are otherwise invisible to conventional reflected light or BSE imaging. Beyond providing new insights into ore genesis and superimposed events, the two techniques enable a detailed understanding of the grain-scale distribution of minor elements. Such information is pivotal for efforts intended to develop new ways to recover value components (precious and critical metals), as well as remove deleterious components of the ore using low-energy, low-waste ore processing methods. Full article

(This article belongs to the Special Issue Microanalysis Applied to Mineral Deposits)

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33 pages, 4723 KiB

Open AccessFeature PaperArticle

Beneficiation of High-Density Tantalum Ore in the REFLUX™ Concentrating Classifier Analysed Using Batch Fractionation Assay and Density Data

by Simon M. Iveson, Nicolas Boonzaier and Kevin P. Galvin

Minerals 2024, 14(2), 197; https://doi.org/10.3390/min14020197 - 14 Feb 2024

Viewed by 754

Abstract

A laboratory-scale REFLUX™ Concentrating Classifier was operated in continuous mode to beneficiate a sub 0.100 mm tantalum ore with a head grade of 0.56 wt.% Ta. The unit incorporated a lower section with a reduced diameter to accommodate a low yield. At a [...] Read more.

A laboratory-scale REFLUX™ Concentrating Classifier was operated in continuous mode to beneficiate a sub 0.100 mm tantalum ore with a head grade of 0.56 wt.% Ta. The unit incorporated a lower section with a reduced diameter to accommodate a low yield. At a yield to underflow product of 4.0 wt.%, a product grade of 13.3 wt.% was achieved (23.7 upgrade) at a recovery of 88.3%. Samples of the feed, product and reject were then fractionated in a batch REFLUX™ Classifier unit using dense lithium heteropolytungstate (LST) solution into 11 fractions. Each of these fractions was then screened into seven size intervals and analysed by pycnometry and X-ray fluorescence (XRF). Most of the material was found to reside in four relatively narrow density bands. A new analysis based on the recovery of selected tracer elements showed that the partition curve had good closure at both ends and that the density cut point and Ep both increased with decreasing particle size. For the +0.045 mm material, the density cut point was estimated to be around 3952 kg/m³ with an Ep of 317 kg/m³, but it was expected that this new method could overestimate Ep. An alternative novel approach for estimating the partition performance was developed. This method estimated the cut point and Ep values to be 3764 kg/m³ and 107 kg/m³, respectively. However, sensitivity analysis found that due to the near total absence of material in the density range from 3400 kg/m³ to 4700 kg/m³, the Ep could likely lie anywhere in the range from 0 to 250 kg/m³. The methodology proved useful in establishing these limitations in the analysis. Full article

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

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24 pages, 6178 KiB

Open AccessArticle

Iron-Bearing Minerals in the Boda Claystone Formation: Correspondences with Stages of Evolution Revealed by Mössbauer Spectroscopy

by Károly Lázár, Zoltán Máthé, Tibor Németh, Viktória Kovács-Kis, Sándor Stichleutner and Ivett Kovács

Minerals 2024, 14(2), 196; https://doi.org/10.3390/min14020196 - 14 Feb 2024

Viewed by 741

Abstract

The Boda Claystone Formation (BCF) is an extended sedimentary sequence formed in a shallow-water salt lake under semi-arid to arid climatic conditions during the middle Permian period. The rock was formed predominantly from denuded and altered products of three primary felsic sources, the [...] Read more.

The Boda Claystone Formation (BCF) is an extended sedimentary sequence formed in a shallow-water salt lake under semi-arid to arid climatic conditions during the middle Permian period. The rock was formed predominantly from denuded and altered products of three primary felsic sources, the Mórágy Metagranite Complex, the Baksa Metamorphic Complex and the rhyolitic Gyűrűfű Formation, resulting in the recent dominant sheet silicate components, illite and chlorite. BCF has been considered a potential host rock for high-level nuclear waste, too. Thus, it has been characterized by several powerful methods so far (X-ray diffraction (XRD), transmission electron microscopy (TEM), etc.). ⁵⁷Fe Mössbauer spectroscopy may provide a unique additional tool to study iron-bearing minerals. Iron is dominantly present in a ferrous form in minerals of the fresh parent rocks (in the biotite group and amphibole), and in a ferric oxide, hematite, in altered Gyűrűfű Formation. During transformations of biotite group minerals and amphibole, the partial release of ferrous iron or its conversion to ferric form takes place with the stabilization of recent illite and chlorite, while the original layered structure is still preserved. Mössbauer spectroscopy revealed the dominant presence of ferrous iron located in cis-M2 octahedral sites both in parent biotite group minerals and in the final illite, as well as chlorite in both stages. The proportion of ferrous iron in biotite group minerals was halved during the stages of evolution by conversion to ferric iron still in sheet silicate illite or by segregation into separate hematite inclusions. The transformation process of biotite group minerals and amphibole of the source rocks is connected only to the iron-bearing smaller fraction of sheet silicates in the BCF clay mineral assemblage. Determination of Fe²⁺/Fe³⁺ ratios in sheet silicates was also pertinent in two sections of BCF. Namely, in samples from the Gorica region, Fe³⁺ was dominant, siting in illite, whereas Fe²⁺ was also present in significant portions in chlorite in samples from the Western Mecsek Anticline. The interpretation is deduced in correspondence with results of extended XRD, and high-resolution TEM studies. Full article

(This article belongs to the Special Issue Advances in the Applications of Mössbauer Spectroscopy for Studies of Iron-Bearing Minerals)

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25 pages, 8742 KiB

Open AccessArticle

Genesis of Gabbroic Hosted Copper Mineralisations in the Albanian Mirdita Zone (Kçira, Thirra)

by Anikó Váczi-Lovász, Zoltán Kovács and Gabriella B. Kiss

Minerals 2024, 14(2), 195; https://doi.org/10.3390/min14020195 - 13 Feb 2024

Viewed by 683

Abstract

There is a wide variety of ore deposits in Albania, where 20% of the Cu resources belong to a deposit type of unknown genesis (sulphide-bearing quartz veins in gabbroic rocks). The focus of this paper is on two mineralisations of this type (Kçira [...] Read more.

There is a wide variety of ore deposits in Albania, where 20% of the Cu resources belong to a deposit type of unknown genesis (sulphide-bearing quartz veins in gabbroic rocks). The focus of this paper is on two mineralisations of this type (Kçira and Thirra) in the Mirdita Zone, an ophiolite zone representing the Mesozoic Neotethys Ocean in the Dinarides. Our aim is to understand the ore-forming processes and the genesis of these deposits, which can be used in future exploration projects. According to the petrographical analysis, the host rock suffered propylitic alteration or subgreenschist facies metamorphism. Mineral chemistry of pyrite and epidote suggests a VMS related origin, more precisely, the deeper part of its stockwork feeder zone. The bulk rock geochemical analyses confirms that the mineralisations are classified as mafic-, Cyprus-type VMS deposits. Differences in the geochemical compositions and the corresponding mineralogical observations are attributed to the distinct original geotectonic positions: higher amount of compatible elements (Cr, Ni, V and Cu) occur in Kçira, which formed in a mid-oceanic ridge environment, while incompatible elements (Ag, As, Co and Zn) are more abundant in the Thirra deposit, which formed in a supra-subduction zone setting. Full article

(This article belongs to the Special Issue Submarine Volcanism, Related Hydrothermal Systems and Mineralizations)

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16 pages, 4278 KiB

Open AccessArticle

From the Mountain and the Sea: Provenance of the Stones of the Prehistoric La Pastora Tholos (Valencina de la Concepción, Seville, Spain)

by Luis Miguel Cáceres, Teodosio Donaire, Samuel Ramírez-Cruzado, Juan Manuel Vargas, Fernando Muñiz, Mónica Martín, Joaquín Rodríguez-Vidal, Francisco Ruiz and Leonardo García Sanjuán

Minerals 2024, 14(2), 194; https://doi.org/10.3390/min14020194 - 12 Feb 2024

Viewed by 783

Abstract

La Pastora tholos is the most complete and characteristic megalithic monument of the Valencina de la Concepción-Castilleja de Guzmán mega-site. This monument was built using three types of rock, each with different functions and coming from three different places: Paleozoic quartzarenite, granite, and [...] Read more.

La Pastora tholos is the most complete and characteristic megalithic monument of the Valencina de la Concepción-Castilleja de Guzmán mega-site. This monument was built using three types of rock, each with different functions and coming from three different places: Paleozoic quartzarenite, granite, and Tertiary calcareous sandstone. A detailed petrological study of the rocks of the tholos and outcrops of similar rocks in the surroundings has been carried out, locating the possible source areas in areas at least 30 km to the N of the monument for the quartzarenite, 15 km for the granite, and 15 km to the S for the sandstone. Therefore, the community that built the monument has a high knowledge of the nature by, which allows them to locate these resources, and a sufficient social organization to exploit them and move them to the mega-site. In this sense, the layout of the outcrops suggests the possible use of boats or rafts to facilitate their displacement, or at least part of their movement. Full article

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25 pages, 6612 KiB

Open AccessArticle

Skarn Formation and Zn–Cu Mineralization in the Dachang Sn Polymetallic Ore Field, Guangxi: Insights from Skarn Rock Assemblage and Geochemistry

by Lei He, Ting Liang, Denghong Wang, Jianxin Zhang and Bosheng Liu

Minerals 2024, 14(2), 193; https://doi.org/10.3390/min14020193 - 12 Feb 2024

Viewed by 860

Abstract

The Dachang is a world-class, super-giant Sn polymetallic ore field mainly composed of Zn–Cu ore bodies proximal to the granitic pluton and Sn polymetallic ore bodies distal to the granitic pluton. In this study, we used petrographic studies and major and trace element [...] Read more.

The Dachang is a world-class, super-giant Sn polymetallic ore field mainly composed of Zn–Cu ore bodies proximal to the granitic pluton and Sn polymetallic ore bodies distal to the granitic pluton. In this study, we used petrographic studies and major and trace element geochemistry with calc-silicates from the Zn–Cu ore bodies to constrain the physicochemical conditions of hydrothermal fluids during skarn rock formation and the evolution of ore-forming elements. Two skarn stages were identified based on petrographic observations: Prograde skarn rocks (Stage I), containing garnet, vesuvianite, pyroxene, wollastonite, and retrograde skarn rocks (Stage II), containing axinite, actinolite, epidote, and chlorite. The retrograde skarn rocks are closely associated with mineralization. The geochemical results show that the garnets in the Dachang ore field belong to the grossular–andradite solid solution, in which the early generation of garnet is mainly composed of grossular (average Gro₇₂And₂₅), while the later generation of garnet is mainly composed of andradite (average Gro₃₉And₅₉); the vesuvianites are Al-rich vesuvianites; the pyroxenes form a diopside–hedenbergite solid solution with a composition of Di_3–86Hd_14–96; the axinites are mainly composed of ferroaxinite; and the actinolites are Fe-actinolite. The mineral assemblage of the skarn rocks indicates that the ore-forming fluid was in a relatively reduced state in the early prograde skarn stage. As the ore-forming fluid evolved, the oxygen fugacity of the ore-forming fluid increased. During the final skarn stage, the ore-forming fluid changed from a relatively oxidized state to a reduced state. The skarn rocks have evolved from early Al-rich to late Fe-rich characteristics, indicating that the early ore-forming fluid was mainly magmatic exsolution fluid, which may mainly reflect the characteristics of magmatic fluids, and the late Fe-rich characteristics of the skarn rocks may indicate that the late hydrothermal fluid was strongly influenced by country rocks. Trace element analyses showed that the Sn content decreased from the prograde skarn stage to the retrograde skarn stage, indicating that Sn mineralization was not achieved by activating and extracting Sn from prograde skarn rocks by hydrothermal fluids. The significant enrichment of Sn in the magmatic hydrothermal fluid is a necessary condition for Sn mineralization. There are various volatile-rich minerals such as axinite, vesuvianite, fluorite, and tourmaline in the Dachang ore field, indicating that the ore-forming fluid contained extensive volatiles B and F, which may be the fundamental reason for the large-scale mineralization of the Dachang ore field. Full article

(This article belongs to the Special Issue Metallogenic Regularity and Metallographic Prediction of Strategic Deposits)

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13 pages, 3417 KiB

Open AccessArticle

Combined Scanned Macro X-Ray Fluorescence and Reflectance Spectroscopy Mapping on Corroded Ancient Bronzes

by Jacopo Orsilli and Simone Caglio

Minerals 2024, 14(2), 192; https://doi.org/10.3390/min14020192 - 12 Feb 2024

Viewed by 922

Abstract

Bronze is an alloy composed primarily of copper and tin and since its discovery is widespread in the whole world. This alloy can thus be found in many archaeological sites and its study can give information about the technology of production, the trading [...] Read more.

Bronze is an alloy composed primarily of copper and tin and since its discovery is widespread in the whole world. This alloy can thus be found in many archaeological sites and its study can give information about the technology of production, the trading routes, or the warfare within a region. However, bronze artefacts can undergo severe alteration processes, and the formation of corrosion layers of different copper minerals can prevent the readability of the artefact or even destroy it, as in the case of the ‘bronze disease’. Their preservation is crucial for maintaining a connection to our cultural heritage. In this paper, we present the study of some corroded bronze artefacts found in different burying conditions. They have been analysed through a scanner system that combines two non-invasive techniques, macro XRF (MA-XRF) and visible, near infrared, short wave infrared (VIS-NIR-SWIR) reflectance, to unravel information about the metal and the patina composition, thickness, and distribution. As the corrosion of bronze depends on the burying conditions and the alloy composition, these data are of the utmost importance to understanding the alteration processes occurring in the archaeological site and to ensure the artefacts’ optimal preservation. Full article

(This article belongs to the Special Issue Characterization and Provenance of Archaeological Materials Using Multi-Method Analysis)

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35 pages, 37975 KiB

Open AccessArticle

Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin

by Argos Belmonte Silveira Schrank, Thisiane Dos Santos, Sabrina Danni Altenhofen, William Freitas, Elias Cembrani, Thiago Haubert, Felipe Dalla Vecchia, Rosalia Barili, Amanda Goulart Rodrigues, Anderson Maraschin and Luiz Fernando De Ros

Minerals 2024, 14(2), 191; https://doi.org/10.3390/min14020191 - 11 Feb 2024

Viewed by 1247

Abstract

The giant Pre-salt reservoirs represent most of the oil production in Brazil. The main Aptian sag reservoirs were deposited in a unique and highly complex hyper-alkaline lacustrine setting. These deposits are essentially constituted by fascicular and spherulitic calcite precipitated in a magnesian clay [...] Read more.

The giant Pre-salt reservoirs represent most of the oil production in Brazil. The main Aptian sag reservoirs were deposited in a unique and highly complex hyper-alkaline lacustrine setting. These deposits are essentially constituted by fascicular and spherulitic calcite precipitated in a magnesian clay matrix (stevensite, kerolite, and saponite/hectorite). Although vital for understanding the origin and main reservoir quality control, the genesis and interactions of clays and carbonates are still poorly constrained. The detailed petrographic description was focused on 812 thin sections from five wells drilled in the Santos Basin Aptian Barra Velha Formation, combined with cathodoluminescence, UV epifluorescence, and X-ray diffraction analyses. The main syngenetic processes were the deposition of finely laminated peloidal and ooidal Mg-clays, the formation of fascicular calcite crusts on the sediment–water interface, and the redeposition of these materials as intraclasts. Abundant clay peloids engulfed in syngenetic shrubs indicate that calcite and clay precipitation was concomitant, though with highly variable rates. Eodiagenetic phases include matrix-replacive and -displacive spherulites and fascicular shrubs; matrix-replacive blocky calcite and dolomite; lamellar carbonates filling matrix shrinkage pores; and microcrystalline calcite, dolomite, and silica replacing the Mg-clay matrix. The preferential dolomitization and calcitization of peloidal layers were most likely due to their higher permeability and larger specific surface. Matrix-replacive saddle dolomite, macrocrystalline calcite, and dawsonite are interpreted as mesodiagenetic or hydrothermal phases after significant matrix dissolution. Unraveling the processes of the formation and alteration of the carbonates and clays and their interactions in the Pre-salt deposits is essential for constraining the depositional and diagenetic conditions in their unique environments and their diagenetic overprinting and for decreasing the exploration risks and increasing the production of those extraordinary reservoirs. Full article

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15 pages, 3309 KiB

Open AccessArticle

5-Dodecylsalicylaldoxime as a Novel Collector in Cassiterite Flotation: Performance and Mechanism

by Lei Sun, Yi Qiao, Yang Cao, Qingqing Wang, Xin Wang, Wei Sun and Guobin Liu

Minerals 2024, 14(2), 190; https://doi.org/10.3390/min14020190 - 11 Feb 2024

Viewed by 744

Abstract

Hydroxamic acid and fatty acid collectors are commonly used in cassiterite flotation but face issues like poor selectivity, high dosage, and strict requirements on ore composition and grinding fineness. This study investigates the collecting performance of a novel flotation reagent, 5-dodecylsalicylaldoxime (DSA), in [...] Read more.

Hydroxamic acid and fatty acid collectors are commonly used in cassiterite flotation but face issues like poor selectivity, high dosage, and strict requirements on ore composition and grinding fineness. This study investigates the collecting performance of a novel flotation reagent, 5-dodecylsalicylaldoxime (DSA), in cassiterite flotation. DSA exhibits remarkable selectivity, achieving an impressive 82.5% recovery of Sn at a concentration of only 9 × 10⁻⁵ mol/L in single mineral flotation tests. Moreover, DSA significantly outperforms benzohydroxamic acid (BHA), enhancing Sn recovery by 33.55% in artificially mixed ore flotation experiments. In the flotation test of a copper–tin polymetallic ore, compared with the BHA flotation effect, the recovery rate of DSA increased by 12.29% when the Sn grade remained basically unchanged. Analyses such as zeta potential, FT-IR, and XPS indicate that DSA’s superior collecting performance stems from its stable adsorption onto cassiterite surfaces through a chelating ring formation, resembling the adsorption mechanism of hydroxamic acid collectors. Furthermore, DSA’s larger cluster size in the solution compared to BHA contributes to its enhanced selectivity and collectability. Overall, DSA emerges as a promising alternative to traditional cassiterite flotation collectors, offering a combination of enhanced selectivity, lower dosage requirements, and robustness in complex ore systems. Full article

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

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19 pages, 6889 KiB

Open AccessArticle

Preparation of Silicon Carbide Powder from Amorphous Silica and Investigation of Synthesis Mechanism

by Xuqin Duan, Shuaiyu Lu, Xiaocui Jiang, Tong Liu and Huifen Yang

Minerals 2024, 14(2), 189; https://doi.org/10.3390/min14020189 - 11 Feb 2024

Cited by 1 | Viewed by 794

Abstract

An innovative process for preparing silicon carbide (SiC) from acid leaching residue of ferronickel slag through a carbon–thermal reduction process was proposed in this study. The results indicate that the acid leaching residue is an ideal silicon source for SiC preparation according to [...] Read more.

An innovative process for preparing silicon carbide (SiC) from acid leaching residue of ferronickel slag through a carbon–thermal reduction process was proposed in this study. The results indicate that the acid leaching residue is an ideal silicon source for SiC preparation according to its high amorphous silica content of 84.20% and fine particle size of d₅₀ = 29.16 μm. Compared with carbon black, activated carbon, and graphite, coke is the more appropriate carbon source for SiC preparation. A micron-size SiC powder with grade of 88.90% and an average particle size (d₅₀) of 44.68 μm can be obtained under the following conditions: the mass ratio of coke to leaching residue as 1.2:1, in an air atmosphere, reducing at 1600 °C for 3 h, following by decarbonizing at 700 °C for 4 h. The XRD, SEM and FTIR analyses show that the prepared powder is 3C-SiC and belongs to the β-SiC crystal type. Based on thermodynamic analysis and micromorphology observation, it can be concluded that with amorphous silica as the silicon source, the carbon–thermal synthesis of SiC powder follows both the solid–solid reaction mechanism and the gas–solid mechanism. The SiC created through solid–solid reaction is primarily nucleated in situ on amorphous SiO₂, with a size close to that of the original acid-leaching slag, while the SiC generated according to the gas–solid mechanism mainly nucleates heterogeneously on the surface of carbon particles, resulting in a smaller particle size and mostly adhering to the surface of solid–solid nucleated SiC particles. This study provides a feasible method for the effective utilization of amorphous silica, which is also significant for the efficient consumption of the vast acid leaching residue. Full article

(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)

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19 pages, 10995 KiB

Open AccessArticle

Iron–Titanium Oxide–Apatite–Sulfide–Sulfate Microinclusions in Gabbro and Adakite from the Russian Far East Indicate Possible Magmatic Links to Iron Oxide–Apatite and Iron Oxide–Copper–Gold Deposits

by Pavel Kepezhinskas, Nikolai Berdnikov, Valeria Krutikova and Nadezhda Kozhemyako

Minerals 2024, 14(2), 188; https://doi.org/10.3390/min14020188 - 11 Feb 2024

Viewed by 885

Abstract

Mesozoic gabbro from the Stanovoy convergent margin and adakitic dacite lava from the Pliocene–Quaternary Bakening volcano in Kamchatka contain iron–titanium oxide–apatite–sulfide–sulfate (ITOASS) microinclusions along with abundant isolated iron–titanium minerals, sulfides and halides of base and precious metals. Iron–titanium minerals include magnetite, ilmenite and [...] Read more.

Mesozoic gabbro from the Stanovoy convergent margin and adakitic dacite lava from the Pliocene–Quaternary Bakening volcano in Kamchatka contain iron–titanium oxide–apatite–sulfide–sulfate (ITOASS) microinclusions along with abundant isolated iron–titanium minerals, sulfides and halides of base and precious metals. Iron–titanium minerals include magnetite, ilmenite and rutile; sulfides include chalcopyrite, pyrite and pyrrhotite; sulfates are represented by barite; and halides are predominantly composed of copper and silver chlorides. Apatite in both gabbro and adakitic dacite frequently contains elevated chlorine concentrations (up to 1.7 wt.%). Mineral thermobarometry suggests that the ITOASS microinclusions and associated Fe-Ti minerals and sulfides crystallized from subduction-related metal-rich melts in mid-crustal magmatic conduits at depths of 10 to 20 km below the surface under almost neutral redox conditions (from the unit below to the unit above the QFM buffer). The ITOASS microinclusions in gabbro and adakite from the Russian Far East provide possible magmatic links to iron oxide–apatite (IOA) and iron oxide–copper–gold (IOCG) deposits and offer valuable insights into the early magmatic (pre-metasomatic) evolution of the IOA and ICOG mineralized systems in paleo-subduction- and collision-related geodynamic environments. Full article

(This article belongs to the Special Issue Iron-Oxide-Apatite Deposits and Fe Skarn Deposits: Genesis, Similarities, and Differences)

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29 pages, 7624 KiB

Open AccessFeature PaperArticle

Chemical and Textural Peculiarities of Zircon from Peralkaline Granites and Quartz-Bearing Syenites

by Karel Breiter, Jindřich Kynický and Zuzana Korbelová

Minerals 2024, 14(2), 187; https://doi.org/10.3390/min14020187 - 10 Feb 2024

Viewed by 957

Abstract

Zircon from four plutons of peralkaline granites and quartz-bearing syenites, differing in geotectonic positions, petrological and mineralogical compositions, and contents of volatile and trace elements, was studied using SEM, CL, and EPMA with the intention to define typical textural and chemical features of [...] Read more.

Zircon from four plutons of peralkaline granites and quartz-bearing syenites, differing in geotectonic positions, petrological and mineralogical compositions, and contents of volatile and trace elements, was studied using SEM, CL, and EPMA with the intention to define typical textural and chemical features of zircon from peralkaline rocks. In strongly peralkaline Na-pyroxene-bearing rocks represented by the Khan Bogd and Khalzan Buregte plutons (Mongolia), the primary zircon is scarce or missing. Most zircon grains are secondary, originating in hydrothermal stage from primary Zr silicates. They often form globular or radial aggregates. Chemical compositions of zircon in these rocks typically show high contents of Y, moderate contents of REE (thus high Y/Yb values) together with low contents of U and Th and low analytical totals. In mildly peralkaline mica-bearing rocks represented by Ivigtut stock (Groenland) and Madeira pluton (Brazil), the exclusive primary Zr mineral is zircon, mostly of orthomagmatic origin. Its analytical totals approach 100 wt%, enrichment in HREE, resulting in low Y/Yb values, is typical. Zircon populations from two types of peralkaline granitoids can be distinguished from each other and from zircon from S-type granites based on combination of the Zr/Hf, Y/Yb, and U/Th values, or on the Y-Hf-P ternary diagram. Full article

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

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15 pages, 36928 KiB

Open AccessArticle

Hardware and Software Solutions for the Generation of a Database of HSV-Color Characteristics for the Main Ores and Rocks of the Khibiny Massif

by Darya Nikolaevna Shibaeva, Roman Pavlovich Voronin, Alena Arkadievna Kompanchenko, Denis Olegovich Volkov, Danil Alekseevich Asanovich and Victor Vladimirovich Bulatov

Minerals 2024, 14(2), 186; https://doi.org/10.3390/min14020186 - 10 Feb 2024

Viewed by 684

Abstract

This article presents developed hardware and software solutions based on the application of machine vision technology. The hardware and software solutions were created in order to generate a database of HSV-color value for the main ore types, host rocks, and minerals to define [...] Read more.

This article presents developed hardware and software solutions based on the application of machine vision technology. The hardware and software solutions were created in order to generate a database of HSV-color value for the main ore types, host rocks, and minerals to define criteria for the in-process identification of the Khibiny apatite in testing the walls of blasting boreholes. The hardware ensures a multi-parametric assessment of the optical characteristics of samples and minerals located on their surface. The designed software solution allows the user to control the measurement process; systematize a description of the textural and structural features of the sample under study; and process images of the core surface. The resultant database of HSV-color value for the main ores and rocks of the Khibiny massif and their constituent minerals will provide an opportunity to search for criteria for the in-process identification of the Khibiny apatite in a mineral mixture. Full article

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

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15 pages, 7941 KiB

Open AccessArticle

An Environmentally Friendly Sulfuric Acid Decomposition Strategy for Mixed Rare Earth Concentrate

by Shaochun Hou, Bo Zhang, Wenjun Li, Tuo Zhao, Zongyang Da and Chenghong Liu

Minerals 2024, 14(2), 185; https://doi.org/10.3390/min14020185 - 9 Feb 2024

Viewed by 927

Abstract

A novel environmentally friendly one-step decomposition strategy for mixed rare earth concentrate of Bayan Obo in sulfuric acid solution was proposed in this work. In this process, more than 84% of bastnasite and monazite were decomposed in the leaching step at a temperature [...] Read more.

A novel environmentally friendly one-step decomposition strategy for mixed rare earth concentrate of Bayan Obo in sulfuric acid solution was proposed in this work. In this process, more than 84% of bastnasite and monazite were decomposed in the leaching step at a temperature lower than the boiling point of sulfuric acid solution. So, the dilapidation of sulfuric acid in this current proposed process will be reduced to a large extent. The stability region of rare earth ion in the RE(La, Ce, Nd)-F-P-SO₄-H₂O system at 170 °C has been proven through Eh-pH diagrams. The factors influencing decomposition of rare earth concentrate in this process were also investigated and the optimal leaching conditions were determined to be a leaching temperature of 170 °C with an ore/acid ratio of 1:5 (g/mL), a sulfuric acid concentrate of 75% and a leaching time of 80 min. The mineralogical changes occurring during the H₂SO₄ leaching process were investigated by X-ray diffraction and SEM-EDS. The analysis results showed that bastnasite and most of monazite had been decomposed, leaving only a small amount of monazite in the leaching residue. Full article

(This article belongs to the Special Issue Green and Efficient Recovery/Extraction of Rare Earth Resources)

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18 pages, 8068 KiB

Open AccessArticle

Fast Initial Model Design for Electrical Resistivity Inversion by Using Broad Learning Framework

by Tao Tao, Peng Han, Xiao-Hui Yang, Qiang Zu, Kaiyan Hu, Shuangling Mo, Shuangshuang Li, Qiang Luo and Zhanxiang He

Minerals 2024, 14(2), 184; https://doi.org/10.3390/min14020184 - 9 Feb 2024

Viewed by 791

Abstract

The electrical resistivity method is widely used in near-surface mineral exploration. At present, the deterministic algorithm is commonly employed in three-dimensional (3-D) electrical resistivity inversion to obtain subsurface electrical structures. However, the accuracy and efficiency of deterministic inversion rely on the initial model. [...] Read more.

The electrical resistivity method is widely used in near-surface mineral exploration. At present, the deterministic algorithm is commonly employed in three-dimensional (3-D) electrical resistivity inversion to obtain subsurface electrical structures. However, the accuracy and efficiency of deterministic inversion rely on the initial model. In practice, obtaining an initial model that approximates the true subsurface electrical structures remains challenging. To address this issue, we introduce a broad learning (BL) network to determine the initial model and utilize the limited memory quasi-Newton (L-BFGS) algorithm to conduct the 3-D electrical resistivity inversion task. The powerful mapping capability of the BL network enables one to find the model that elucidates the actual observed data. The single-layer BL network makes it efficient and easy to realize, leading to much faster network training compared to that using the deep learning network. Both the synthetic and field experiments suggest that the BL framework could effectively obtain the initial model based on observed data. Furthermore, in comparison to using a homogeneous medium as the initial model, the L-BFGS inversion with the BL framework-designed initial model improves the inversion accuracy of subsurface electrical structures and expedites the convergence speed of the iteration. This study provides an effective approach for fast initial model design in a data-driven manner when the prior information is unavailable. The proposed method can be useful in high-precision imaging of near-surface mineral electrical structures. Full article

(This article belongs to the Special Issue Application of Big Data Mining, Machine Learning and Artificial Intelligence in Ore Deposits)

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14 pages, 5130 KiB

Open AccessArticle

Organic Matter Enrichment Mechanisms in the Lower Cambrian Shale: A Case Study from Xiangandi #1 Well

by Lei Zhou, Xingqiang Feng, Linyan Zhang and Lin Wu

Minerals 2024, 14(2), 183; https://doi.org/10.3390/min14020183 - 8 Feb 2024

Viewed by 652

Abstract

In order to investigate the effect of primary productivity, organic matter dilution, and preservation on the accumulation of organic matter, geochemical data, and proxies of primary productivity, clastic influx, and redox conditions were obtained for organic-rich shales in the Cambrian Niutitang Formation. The [...] Read more.

In order to investigate the effect of primary productivity, organic matter dilution, and preservation on the accumulation of organic matter, geochemical data, and proxies of primary productivity, clastic influx, and redox conditions were obtained for organic-rich shales in the Cambrian Niutitang Formation. The primary productivity (total organic carbon [TOC], Mo, P, Ba, and Babio) and redox (Ni/Co, V/Cr, U/Al, and Th/U) proxies suggest the organic-rich shales were deposited in anoxic-euxinic conditions during periods of high primary productivity. Pyrite in the Niutitang Formation comprises spherical framboids, which also indicate that anoxic bottom waters were present during organic matter deposition. High primary productivity enhanced the organic C flux into the thermocline layer and bottom waters, which lead to the development of anoxic bottom waters owing to O₂ consumption by microorganisms and organic matter degradation. The anoxic bottom waters were beneficial for the preservation of organic matter. In addition, Ti/Al ratios correlate well with TOC contents throughout the Niutitang Formation, indicating that clastic input increased the burial rate and prevented organic matter degradation during deposition. Therefore, the accumulation of organic matter in the Niutitang Formation was controlled mainly by primary productivity rather than bottom-water redox conditions. Full article

(This article belongs to the Topic Hydrocarbon Generation and Accumulation in Unconventional Shale Reservoir: Up-to-Date Advances in Theory, Experiment, Method and Application, Volume II)

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14 pages, 6424 KiB

Open AccessArticle

Petrographic Insights into the Evolution of Nano-Scale Organic Matter Pores with Organic Matter Conversion

by Lei Zhou, Xingqiang Feng, Linyan Zhang, Lin Wu and Rui Zhang

Minerals 2024, 14(2), 182; https://doi.org/10.3390/min14020182 - 8 Feb 2024

Viewed by 729

Abstract

To investigate the influence of organic matter conversion on the evolution of organic matter pores, fractional conversion (TR_HI) and loss of TOC (TOC_L) from the organic matter conversion of Middle Jurassic Dameigou Formation shale samples were calculated using [...] Read more.

To investigate the influence of organic matter conversion on the evolution of organic matter pores, fractional conversion (TR_HI) and loss of TOC (TOC_L) from the organic matter conversion of Middle Jurassic Dameigou Formation shale samples were calculated using petrographic analysis. The TR_HI of organic matter varies from 0.30 to 0.88 and TOC_L content ranges from 0.62% and 4.09%. Relative to samples of Type III organic matter in shales, type II samples exhibit higher TR_HI and TOC_L values. Petrographic calculations of TR_HI reveal that the fractional conversion of different kerogens differs for the same thermal maturity level. The specific surface area (S_BET) ranges between 1.25 and 6.63 m²/g and micropore surface area (S_mic) ranges between 4.16 and 21.27 m²/g. Correlations between pore structure parameters and TOC_L content are higher than those between pore structure parameters and TOC content. The original TOC content decreases with increasing maturity level owing to hydrocarbon generation from organic matter conversion. The development of organic matter pores depends mainly on organic matter conversion, which is influenced by the richness, organic maceral compositions, and thermal maturity of the organic matter. The contents of kaolinite, illite, and mixed-layer illite/smectite (I/S) in the studied shales are 17.83%–37.05%, 5.36%–11.31%, and 5.27%–14.36%, respectively. Pore structure parameters (S_BET and S_mic) exhibit moderate positive correlations with illite content and I/S content, and moderate negative correlations with kaolinite content, indicating that different clay minerals have differential effects on pore structure. Full article

(This article belongs to the Topic Microstructural Analysis of Organic Matter in Shale)

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15 pages, 2827 KiB

Open AccessFeature PaperArticle

Interactions of Perrhenate (Re(VII)O₄⁻) with Fe(II)-Bearing Minerals

by Anthony W. N. Kilber, Maxim I. Boyanov, Kenneth M. Kemner and Edward J. O’Loughlin

Minerals 2024, 14(2), 181; https://doi.org/10.3390/min14020181 - 7 Feb 2024

Viewed by 893

Abstract

Rhenium (Re) is an extremely rare element, with a crustal abundance of approximately 0.4 parts per billion (ppb) and a sea water concentration of 8.3 parts per trillion (ppt). However, Re concentrations in anoxic marine sediments range from 2 to 184 ppb, which [...] Read more.

Rhenium (Re) is an extremely rare element, with a crustal abundance of approximately 0.4 parts per billion (ppb) and a sea water concentration of 8.3 parts per trillion (ppt). However, Re concentrations in anoxic marine sediments range from 2 to 184 ppb, which is attributed to reduction of the highly soluble perrhenate ion (Re(VII)O₄⁻) to insoluble Re(IV) species. Anoxic sediments typically contain Fe(II) and sulfide species, which could potentially reduce Re(VII) to Re(IV). In this study, we examined the interactions of KReO₄ with magnetite (Fe₃O₄), siderite (FeCO₃), vivianite (Fe₃(PO₄)₂•8H₂O), green rust (mixed Fe(II)/Fe(III) layered double hydroxide), mackinawite (FeS), and chemically reduced nontronite (NAu-1) using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy to determine the valence state and speciation of Re. Uptake of Re by green rust was rapid, with ~50% associated with the solids within 2 days. In contrast, there was <10% uptake by the other Fe(II) phases over 48 days. Reduction of Re(VII) to Re(IV) was only observed in the presence of green rust, producing clusters of bidentate-coordinated Re(IV)O₆ octahedra.. These results suggest that except for green rust, the potential for other Fe(II)-bearing minerals to act as reductants for ReO₄⁻ in sedimentary environments requires further investigation. Full article

(This article belongs to the Special Issue Redox Reactivity of Iron Minerals in the Geosphere, 2nd Edition)

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16 pages, 6295 KiB

Open AccessArticle

Enhancing Flame Retardancy: Enrichment of Huntite for Paint Industry Applications

by Tülay Türk, Zeynep Üçerler, İpek Sökmen and Murat Olgaç Kangal

Minerals 2024, 14(2), 180; https://doi.org/10.3390/min14020180 - 7 Feb 2024

Viewed by 878

Abstract

Huntite, a naturally occurring carbonate mineral, originates through the alteration processes of dolomite and magnesite. While its structural characteristics align with typical carbonate minerals, its distinction arises from its polyhedral conjunctiveness. The versatile utility of huntite spans several industries, including paint, flame retardant, [...] Read more.

Huntite, a naturally occurring carbonate mineral, originates through the alteration processes of dolomite and magnesite. While its structural characteristics align with typical carbonate minerals, its distinction arises from its polyhedral conjunctiveness. The versatile utility of huntite spans several industries, including paint, flame retardant, plastic, polymer, and pharmaceutical sectors. Noteworthy among its diverse applications is its utilization as a flame-retardant additive in raw materials. In this investigation, three samples received from the Denizli region of Turkey were subjected to detailed analysis followed by an enrichment process involving mechanical attrition and sieving of 38 microns where undersize products were obtained, exhibiting 86.9% huntite for the H-1 sample and 91.9% huntite for the H-2–3 sample. The huntite concentrates were then incorporated into paint formulations with the objective of enhancing flame retardancy. A series of testing protocols were implemented to assess the quality of the resulting paints, ultimately yielding a fire-resistant paint formulation through utilizing the H-1 sample. Full article

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

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18 pages, 4667 KiB

Open AccessArticle

Cooperative Exploration Model of Coal–Lithium Deposit: A Case Study of the Haerwusu Coal–Lithium Deposit in the Jungar Coalfield, Inner Mongolia, Northern China

by Xin Li, Yingchun Wei, Daiyong Cao, Jinhao Wei, Xiangyang Liu, Yun Zhang and Bo Dong

Minerals 2024, 14(2), 179; https://doi.org/10.3390/min14020179 - 7 Feb 2024

Cited by 1 | Viewed by 728

Abstract

Lithium (Li) is an important strategic metal mineral resource, irreplaceable in the fields of modern industry, new energy technology, nuclear fusion, and energy storage devices. Li is an important supplement to traditional strategic metal mineral resources and has become an important avenue of [...] Read more.

Lithium (Li) is an important strategic metal mineral resource, irreplaceable in the fields of modern industry, new energy technology, nuclear fusion, and energy storage devices. Li is an important supplement to traditional strategic metal mineral resources and has become an important avenue of mineral resource exploration. Therefore, there is an urgent need to establish a cooperative exploration model of coal and Li deposits to lay a theoretical foundation from the perspective of technical optimization and economic rationality. This study is based on the distribution characteristics of the Haerwusu coal–Li deposit, and the effectiveness of the response to exploration techniques, the economical and effective exploration techniques, the reasonable exploration engineering design, and resource estimation parameters is investigated. Therefore, the cooperative exploration model of the coal–Li deposit is established. The high-Li areas in the surface of the Haerwusu Li deposit is distributed near the B1 anticline or in the middle area between the X1 syncline and the B1 anticline, and the vertical distribution of Li content is irregular. The exploration techniques, exploration engineering design, and resource estimation are reviewed and optimized. According to the geological, geochemical, and geophysical conditions, a reasonable cooperative exploration model for coal–Li deposits is established from the two aspects of the coordination of multi-mineral exploration and the coordination of various exploration technologies. The determination of the coal–Li deposit cooperative exploration model has important practical significance for improving the resource security system. Full article

(This article belongs to the Special Issue Mineralization Mechanism and Geochemical Characteristics of Coals and Associated Minerals)

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Minerals, Volume 14, Issue 2 (February 2024) – 91 articles

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