Minerals

23 pages, 3976 KiB

Open AccessArticle

Hydrologic and Water Quality Modeling of the Pebble Mine Project Pit Lake and Downstream Environment after Mine Closure

by Ann Maest, Robert Prucha and Cameron Wobus

Minerals 2020, 10(8), 727; https://doi.org/10.3390/min10080727 - 18 Aug 2020

Cited by 8 | Viewed by 4275

The Pebble Project in Alaska is one of the world’s largest undeveloped copper deposits. The Environmental Impact Statement (EIS) proposes a 20-year open-pit extraction, sulfide flotation, and deposition of separated pyritic tailings and potentially acid-generating waste rock in the pit at closure. The [...] Read more.

The Pebble Project in Alaska is one of the world’s largest undeveloped copper deposits. The Environmental Impact Statement (EIS) proposes a 20-year open-pit extraction, sulfide flotation, and deposition of separated pyritic tailings and potentially acid-generating waste rock in the pit at closure. The pit will require perpetual pump and treat management. We conducted geochemical and integrated groundwater–surface water modeling and streamflow mixing calculations to examine alternative conceptual models and future mine abandonment leading to failure of the water management scheme 100 years after mine closure. Using EIS source water chemistry and volumes and assuming a well-mixed pit lake, PHREEQC modeling predicts an acidic (pH 3.5) pit lake with elevated copper concentrations (130 mg/L) under post-closure conditions. The results are similar to water quality in the Berkeley Pit in Montana, USA, another porphyry copper deposit pit lake in rocks with low neutralization potential. Integrated groundwater–surface water modeling using MIKE SHE examined the effects of the failure mode for the proposed 20-year and reasonably foreseeable 78-year expansion. Simulations predict that if pumping fails, the 20-year pit lake will irreversibly overtop within 3 to 4 years and mix with the South Fork Koktuli River, which contains salmon spawning and rearing habitat. The 78-year pit lake overtops more rapidly, within 1 year, and discharges into Upper Talarik Creek. Mixing calculations for the 20-year pit show that this spillover would lead to exceedances of Alaska’s copper surface water criteria in the river by a factor of 500–1000 times at 35 miles downstream. The combined modeling efforts show the importance of examining long-term failure modes, especially in areas with high potential impacts to stream ecological services. Full article

(This article belongs to the Special Issue Environmental Geochemistry of Mineral Deposits)

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16 pages, 3155 KiB

Open AccessArticle

Rheology of Alkali-Activated Mortars: Influence of Particle Size and Nature of Aggregates

by Sara Gismera, María del Mar Alonso, Marta Palacios and Francisca Puertas

Minerals 2020, 10(8), 726; https://doi.org/10.3390/min10080726 - 18 Aug 2020

Cited by 8 | Viewed by 2259

Abstract

The effect of two precursors (slag and fly ash), different particle size distribution, and three types of aggregate (siliceous sand, limestone, and recycled concrete) on alkali-activated material (AAM) mortar rheology were studied and compared to their effect on an ordinary Portland Cement (OPC) [...] Read more.

The effect of two precursors (slag and fly ash), different particle size distribution, and three types of aggregate (siliceous sand, limestone, and recycled concrete) on alkali-activated material (AAM) mortar rheology were studied and compared to their effect on an ordinary Portland Cement (OPC) mortar reference. Stress growth and flow curve tests were conducted to determine plastic viscosity and static and dynamic yield stress of the AAM and OPC mortars. In both OPC and AAM mortars, a reduction of the aggregate size induces a rise of the liquid demand to preserve the plastic consistency of the mortar. In general terms, an increase of the particle size of the siliceous aggregates leads to a decrease of the measured rheological parameters. The AAM mortars require higher liquid/solid ratios than OPC mortars to attain plastic consistency. AAM mortars proved to be more sensitive than OPC mortars to changes in aggregate nature. The partial replacement of the siliceous aggregates with up to 20% of recycled concrete aggregates induced no change in mixing liquid uptake, in either AAM or OPC mortars. All the AAM and OPC mortars studied fitted to the Bingham model. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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23 pages, 17959 KiB

Open AccessArticle

Application of Historical Geophysical Materials in Searching for Cu-Ag Ore Deposits—A New Direction of Research

by Stanisław Speczik, Lidia Dziewińska, Waldemar Jóźwiak and Krzysztof Zieliński

Minerals 2020, 10(8), 725; https://doi.org/10.3390/min10080725 - 18 Aug 2020

Cited by 6 | Viewed by 2161

Abstract

This paper presents a new instrument in geological exploration, which uses historical geophysical data for the indication of potential zones of the occurrence of Cu-Ag ore, based on the example of the newly discovered Nowa Sól deposit in south-western Poland. Basic historical seismic [...] Read more.

This paper presents a new instrument in geological exploration, which uses historical geophysical data for the indication of potential zones of the occurrence of Cu-Ag ore, based on the example of the newly discovered Nowa Sól deposit in south-western Poland. Basic historical seismic and gravimetric data were applied along with transformed maps. The new method of effective reflection coefficients (ERC) allowed the utilization of archival seismic records for a more precise determination of the most vaguely traced interfaces within the Permian Zechstein unit. Compared to an amplitude-based seismic section, an ERC section is characterized by its highly increased resolution of imaging. The tracing of changes in the facies and the tectonics of Zechstein sediments, particularly in a zone of their contact with Rotliegend rocks, along with the new ERC method, enabled the establishing of precise locations of prospecting boreholes. The combined use of ERC and historical well logs also allowed more precise identification of the shape of oxidized areas and the adjacent orebodies. Full article

(This article belongs to the Special Issue Novel Methods and Applications for Mineral Exploration, Volume II)

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25 pages, 12361 KiB

Open AccessArticle

pXRF Measurements on Soil Samples for the Exploration of an Antimony Deposit: Example from the Vendean Antimony District (France)

by Bruno Lemière, Jeremie Melleton, Pascal Auger, Virginie Derycke, Eric Gloaguen, Loïc Bouat, Dominika Mikšová, Peter Filzmoser and Maarit Middleton

Minerals 2020, 10(8), 724; https://doi.org/10.3390/min10080724 - 18 Aug 2020

Cited by 5 | Viewed by 3725

Abstract

Mineral exploration is increasingly challenging in inhabited areas. To evaluate the potential of soil analysis by pXRF (portable X-ray fluorescence) as a low-footprint exploration technique, we revisited a historic Sb district in an agricultural area and performed shallow-soil sampling (Ah and B horizons) [...] Read more.

Mineral exploration is increasingly challenging in inhabited areas. To evaluate the potential of soil analysis by pXRF (portable X-ray fluorescence) as a low-footprint exploration technique, we revisited a historic Sb district in an agricultural area and performed shallow-soil sampling (Ah and B horizons) along profiles across known veins to capture the endogenic geochemical anomaly signals. Despite an expected bias between pXRF measurements and laboratory analyses, the former effectively located the Sb veins, especially when using their multi-element capabilities. Composition data processing (CoDa) and horizon-selective sampling significantly improved the method’s efficiency. On-site measurements allow dynamic sampling and mapping, helping with faster, cost-effective sample selection for further laboratory investigations. Based on this case study, where similar geochemical patterns were obtained for both horizons, application of an on-site approach to a humic horizon can increase survey efficiency and decrease impacts. Full article

(This article belongs to the Special Issue Critical Metals in Hydrothermal Ores: Resources, Recovery, and Challenges)

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7 pages, 198 KiB

Open AccessEditorial

Editorial for the Special Issue “Properties of Melt and Minerals at High Pressures and High Temperature”

by Claudia Romano

Minerals 2020, 10(8), 723; https://doi.org/10.3390/min10080723 - 18 Aug 2020

Cited by 1 | Viewed by 1652

Abstract

This Special Volume sets out to summarize knowledge in the rapidly developing area of the high-pressure and high-temperature properties and structure of silicate melts and minerals [...] Full article

(This article belongs to the Special Issue Properties of Melt and Minerals at High Pressures and High Temperatures)

21 pages, 5368 KiB

Open AccessArticle

Production, Reserves, and Processing of Feldspar and Feldspathoid Rocks in the Czech Republic from 2005 to 2019—An Overview

by Jan Zahradník, Jakub Jirásek, Jaromír Starý and Martin Sivek

Minerals 2020, 10(8), 722; https://doi.org/10.3390/min10080722 - 17 Aug 2020

Cited by 5 | Viewed by 7250

Abstract

This paper aims to characterize and interpret the trends in reserves, resources, and mine production of feldspar and feldspathoid rocks during 2005–2019 in the Czech Republic. With over 101 Mt of total resources and 22 Mt of reserves, feldspar belongs to the crucial [...] Read more.

This paper aims to characterize and interpret the trends in reserves, resources, and mine production of feldspar and feldspathoid rocks during 2005–2019 in the Czech Republic. With over 101 Mt of total resources and 22 Mt of reserves, feldspar belongs to the crucial industrial minerals of the Czech Republic. With annual outputs of approximately 400–450 kt of feldspars and 20–35 kt of feldspathoid rocks (nepheline syenite), the Czech Republic ranks among the top European and world feldspar producers. Most of the production comes from leucocratic granitoid rocks (key active deposit: Krásno-Vysoký Kámen), followed by sedimentary rocks (key active deposit: Halámky), and granitic pegmatites (key active deposit: Luženičky). Nepheline syenite is mined at a single deposit. All deposits are extracted from open pits (quarries). Ongoing geological prospecting and exploration for new deposits are increasing available reserves and resources. The feldspar raw materials are used in the domestic glass and ceramic industries, while more than 50% is exported, generally to Poland and Germany. Full article

(This article belongs to the Special Issue Industrial Minerals)

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19 pages, 5739 KiB

Open AccessArticle

Assessing Options for Remediation of Contaminated Mine Site Drainage Entering the River Teign, Southwest England

by Abigail Jordan, Rachel Hill, Adrienne Turner, Tyrone Roberts and Sean Comber

Minerals 2020, 10(8), 721; https://doi.org/10.3390/min10080721 - 17 Aug 2020

Cited by 3 | Viewed by 3655

Abstract

The river Teign in Devon has come under scrutiny for failing to meet environmental quality standards for ecotoxic metals due to past mining operations. A disused mine known as Bridford Barytes mine, has been found to contribute a significant source of Zn, Cd [...] Read more.

The river Teign in Devon has come under scrutiny for failing to meet environmental quality standards for ecotoxic metals due to past mining operations. A disused mine known as Bridford Barytes mine, has been found to contribute a significant source of Zn, Cd and Pb to the river. Recently, studies have been focused on the remediation of such mine sites using low-cost treatment methods to help reduce metal loads to the river downstream. This paper explores the metal removal efficiency of red mud, a waste product from the aluminium industry, which has proven to be an attractive low-cost treatment method for adsorbing toxic metals. Adsorption kinetics and capacity experiments reveal metal removal efficiencies of up to 70% within the first 2 h when red mud is applied in pelletized form. Further, it highlights the potential of biochar, another effective adsorbent observed to remove >90% Zn using agricultural feedstock. Compliance of the Teign has been investigated by analysing dissolved metal concentrations and bioavailable fractions of Zn to assess if levels are of environmental concern. By applying a real-world application model, this study reveals that compressed pellets and agricultural biochar offer an effective, low-cost option to reducing metal concentrations and thus improving the quality of the river Teign. Full article

(This article belongs to the Special Issue Sustainable Use of Abandoned Mines)

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22 pages, 9532 KiB

Open AccessReview

New Data on the Isomorphism in Eudialyte-Group Minerals. 2. Crystal-Chemical Mechanisms of Blocky Isomorphism at the Key Sites

by Ramiza K. Rastsvetaeva and Nikita V. Chukanov

Minerals 2020, 10(8), 720; https://doi.org/10.3390/min10080720 - 17 Aug 2020

Cited by 20 | Viewed by 3962

Abstract

The review considers various complex mechanisms of isomorphism in the eudialyte-group minerals, involving both key positions of the heteropolyhedral framework and extra-framework components. In most cases, so-called blocky isomorphism is realized when one group of atoms and ions is replaced by another one, [...] Read more.

The review considers various complex mechanisms of isomorphism in the eudialyte-group minerals, involving both key positions of the heteropolyhedral framework and extra-framework components. In most cases, so-called blocky isomorphism is realized when one group of atoms and ions is replaced by another one, which is accompanied by a change in the valence state and/or coordination numbers of cations. The uniqueness of these minerals lies in the fact that they exhibit ability to blocky isomorphism at several sites of high-force-strength cations belonging to the framework and at numerous sites of extra-framework cations and anions. Full article

(This article belongs to the Special Issue Study of the Eudialyte Group Minerals)

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24 pages, 10805 KiB

Open AccessArticle

Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines

by Misato Shimbashi, Shingo Yokoyama, Yasutaka Watanabe, Tsutomu Sato, Tsubasa Otake, Ryosuke Kikuchi, Minoru Yamakawa and Naoki Fujii

Minerals 2020, 10(8), 719; https://doi.org/10.3390/min10080719 - 17 Aug 2020

Cited by 4 | Viewed by 3442

Abstract

In radioactive waste disposal facilities, low-permeability engineered barrier materials are important for inhibiting radionuclide migration. However, dissolution–precipitation reactions under alkaline conditions change the permeability of engineered barriers. To understand long-term dissolution–precipitation reactions under alkaline conditions in chemically complex systems, trenches and drill holes [...] Read more.

In radioactive waste disposal facilities, low-permeability engineered barrier materials are important for inhibiting radionuclide migration. However, dissolution–precipitation reactions under alkaline conditions change the permeability of engineered barriers. To understand long-term dissolution–precipitation reactions under alkaline conditions in chemically complex systems, trenches and drill holes were excavated at Narra in Palawan, where alkaline fluids (pH > 11) have been naturally produced, seeping into clastic sediments derived from serpentinized ultramafic rocks and gabbro of Palawan ophiolite. Interaction between the alkaline seepage and clastic sediments, which have been deposited since 15,000 radiocarbon years before present (¹⁴C yr BP), led to dissolution of minerals and the precipitation of Si-bearing phases which were divided into two main categories: Fe-Mg-Si infillings and Ca-Si infillings. The former category was composed of iron-magnesium-silicate-hydrate (F-M-S-H) and a nontronite-like mineral and was widely recognized in the clastic sediments. The nontronite-like mineral likely formed by interaction between silicates and alkaline seepage mixed with infiltrated seawater, whereas F-M-S-H formed by the reaction of silicates with alkaline seepage in the absence of seawater infiltration. Ca-Si infillings included 14 Å tobermorite and were precipitated from alkaline seepage combined with the Ca and Si supplied by the dissolution of calcite and silicates in the clastic sediments. Full article

(This article belongs to the Special Issue Emerging Insights into Serpentinites)

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26 pages, 13532 KiB

Open AccessArticle

The Occurrence of Authigenic Clay Minerals in Alkaline-Saline Lakes, Pantanal Wetland (Nhecolândia Region, Brazil)

by Isis Armstrong Dias, Leonardo Fadel Cury, Bruno Guimarães Titon, Gustavo Barbosa Athayde, Guilherme Fedalto, Larissa da Rocha Santos, Ana Paula Soares, Camila de Vasconcelos Müller Athayde and Anelize Manuela Bahniuk Rumbeslperger

Minerals 2020, 10(8), 718; https://doi.org/10.3390/min10080718 - 17 Aug 2020

Cited by 12 | Viewed by 3103

Abstract

Mg clay minerals are usually associated with carbonates in alkaline-saline environments, precipitated from solution and/or transformation from other minerals. The aim of this research is to identify the mineralogy and geochemistry of clay minerals in different alkaline lakes in the Nhecolândia region, the [...] Read more.

Mg clay minerals are usually associated with carbonates in alkaline-saline environments, precipitated from solution and/or transformation from other minerals. The aim of this research is to identify the mineralogy and geochemistry of clay minerals in different alkaline lakes in the Nhecolândia region, the southernmost region of the Pantanal wetland (Brazil). Sediment samples were analyzed by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and transmission electron microscopy. Water samples were analyzed, determining their main cations and anions, in order to understand their relationship with the clays. The analyses allowed classifying the water bodies as saline, oligosaline and freshwater lakes. The sediments are composed mainly of quartz and a fine-clay fraction, dominated by illite, kaolinite and smectite. The XRD results showed illite and smectite mixed-layered in the saline lakes at Barranco Alto farm, whereas at Nhumirim farm, trioctahedral smectite was only observed in one lake. The smectite minerals were normally identified coupled with calcite at the top of the sequences, associated with exopolymeric substances (EPS) in the lakes, suggesting that these minerals are precipitating due to the physical-chemical and biological conditions of the water bodies. Full article

(This article belongs to the Special Issue From Diagenesis to Low-Grade Metamorphism)

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16 pages, 9201 KiB

Open AccessArticle

DEM Simulation of Laboratory-Scale Jaw Crushing of a Gold-Bearing Ore Using a Particle Replacement Model

by Gabriel Kamilo Barrios, Narcés Jiménez-Herrera, Silvia Natalia Fuentes-Torres and Luís Marcelo Tavares

Minerals 2020, 10(8), 717; https://doi.org/10.3390/min10080717 - 14 Aug 2020

Cited by 10 | Viewed by 5272

Abstract

The Discrete Element Method (DEM) is a numerical method that is able to simulate the mechanical behavior of bulk solids flow using spheres or polyhedral elements, offering a powerful tool for equipment design and optimization through modeling and simulation. The present work uses [...] Read more.

The Discrete Element Method (DEM) is a numerical method that is able to simulate the mechanical behavior of bulk solids flow using spheres or polyhedral elements, offering a powerful tool for equipment design and optimization through modeling and simulation. The present work uses a Particle Replacement Model (PRM) embedded in the software EDEM^® to model and simulate operation of a laboratory-scale jaw crusher. The PRM was calibrated using data from single particle slow compression tests, whereas simulations of the jaw crusher were validated on the basis of experiments, with very good agreement. DEM simulations described the performance of the crusher in terms of throughput, product size distribution, compressive force on the jaws surface, reduction ratio, and energy consumption as a function of closed side setting and frequency. Full article

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

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15 pages, 4221 KiB

Open AccessArticle

A Trace Element Classification Tree for Chalcopyrite from Oktyabrsk Deposit, Norilsk–Talnakh Ore District, Russia: LA-ICPMS Study

by Alexander E. Marfin, Alexei V. Ivanov, Vera D. Abramova, Tatiana N. Anziferova, Tatiana A. Radomskaya, Tamara Y. Yakich and Ksenia V. Bestemianova

Minerals 2020, 10(8), 716; https://doi.org/10.3390/min10080716 - 14 Aug 2020

Cited by 10 | Viewed by 3615

Abstract

The Oktyabrsk PGE-Cu-Ni deposit is one of the largest resources in the Norilsk–Talnakh ore district, Russia, and it is viewed as an ore giant on a global scale. It contains three types of ores: massive, disseminated and veinlet-disseminated. The two former ore types [...] Read more.

The Oktyabrsk PGE-Cu-Ni deposit is one of the largest resources in the Norilsk–Talnakh ore district, Russia, and it is viewed as an ore giant on a global scale. It contains three types of ores: massive, disseminated and veinlet-disseminated. The two former ore types were formed by a liquation process, whereas the latter was associated with fluid-induced selective metasomatic replacement of metamorphosed wall rocks. One of the major ore minerals in all ore types is chalcopyrite. In this study, we determined concentrations of trace elements in this mineral using laser ablation inductively coupled plasma mass spectrometry. It appeared that standard geochemical tools, such as plotting the data in the form of diagrams of normalized concentrations, binary and ternary plots, do not allow one to distinguish chalcopyrite from visually and genetically different ore types. In contrast, more advanced statistical methods such as cluster analysis show different groupings of elements for each ore type. Based on the element clustering, a classification tree was suggested, which allowed for the differentiation of massive, disseminated and veinlet-disseminated ore types of the Oktyabrsk deposit by Se, Te, Cd and Pb concentrations in chalcopyrite with a success rate of 86%. The general feature is that chalcopyrite of veinlet-disseminated ore is poorer in these elements compared to chalcopyrite of the two other ore types. Chalcopyrite of massive ore is poorer in Se and Te when compared to chalcopyrite of disseminated ore. Full article

(This article belongs to the Special Issue The Formation of Sulfide Ores in PGE-Cu-Ni Deposits)

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17 pages, 10629 KiB

Open AccessArticle

Decarbonation Reactions Involving Ankerite and Dolomite under upper Mantle P,T-Parameters: Experimental Modeling

by Yuliya V. Bataleva, Aleksei N. Kruk, Ivan D. Novoselov, Olga V. Furman and Yuri N. Palyanov

Minerals 2020, 10(8), 715; https://doi.org/10.3390/min10080715 - 13 Aug 2020

Cited by 11 | Viewed by 3237

Abstract

An experimental study aimed at the modeling of dolomite- and ankerite-involving decarbonation reactions, resulting in the CO₂ fluid release and crystallization of Ca, Mg, Fe garnets, was carried out at a wide range of pressures and temperatures of the upper mantle. Experiments [...] Read more.

An experimental study aimed at the modeling of dolomite- and ankerite-involving decarbonation reactions, resulting in the CO₂ fluid release and crystallization of Ca, Mg, Fe garnets, was carried out at a wide range of pressures and temperatures of the upper mantle. Experiments were performed using a multi-anvil high-pressure apparatus of a “split-sphere” type, in CaMg(CO₃)₂-Al₂O₃-SiO₂ and Ca(Mg,Fe)(CO₃)₂-Al₂O₃-SiO₂ systems (pressures of 3.0, 6.3 and 7.5 GPa, temperature range of 950–1550 °C, hematite buffered high-pressure cell). It was experimentally shown that decarbonation in the dolomite-bearing system occurred at 1100 ± 20 °C (3.0 GPa), 1320 ± 20 °C (6.3 GPa), and 1450 ± 20 °C (7.5 GPa). As demonstrated by mass spectrometry, the fluid composition was pure CO₂. Composition of synthesized garnet was Prp₈₃Grs₁₇, with main Raman spectroscopic modes at 368–369, 559–562, and 912–920 cm⁻¹. Decarbonation reactions in the ankerite-bearing system were realized at 1000 ± 20 °C (3.0 GPa), 1250 ± 20 °C (6.3 GPa), and 1400 ± 20 °C (7.5 GPa). As a result, the garnet of Grs₂₅Alm₄₀Prp₃₅ composition with main Raman peaks at 349–350, 552, and 906–907 cm⁻¹ was crystallized. It has been experimentally shown that, in the Earth’s mantle, dolomite and ankerite enter decarbonation reactions to form Ca, Mg, Fe garnet + CO₂ assemblage at temperatures ~175–500 °C lower than CaCO₃ does at constant pressures. Full article

(This article belongs to the Special Issue Behaviour of Volatiles and Fluid-Mobile Elements in Subduction Zones)

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16 pages, 4447 KiB

Open AccessArticle

Mineralogical Characteristics of Early Permian Paragonite-Bearing Coal (No. 3) in the Jinyuan Mine, Tengxian Coalfield, Shandong Province, Eastern China

by Wenmu Guo, Jinxiao Li, Zhenzhen Wang, Ke Zhang, Zheng Gao, Jialiang Ma and Cunliang Zhao

Minerals 2020, 10(8), 714; https://doi.org/10.3390/min10080714 - 12 Aug 2020

Cited by 3 | Viewed by 2901

Abstract

The Early Permian coal is of great value in the Tengxian Coalfield, Shandon Province, Eastern China. This work deals with the new data focusing on mineralogical characteristics in the Early Permian Shanxi Formation No. 3 coal from the Jinyuan Mine. The Jinyuan coal [...] Read more.

The Early Permian coal is of great value in the Tengxian Coalfield, Shandon Province, Eastern China. This work deals with the new data focusing on mineralogical characteristics in the Early Permian Shanxi Formation No. 3 coal from the Jinyuan Mine. The Jinyuan coal is a low ash and highly volatile A bituminous coal. Minerals in the No. 3 coal mainly comprise of kaolinite, ankerite, illite, calcite, siderite, and quartz, with varying compositions of trace amounts of pyrite, jarosite, bassanite, anatase, and rutile. According to mineral assemblage in the coal plies, three Types (A to C) can be identified in the No. 3 coal. The dominant minerals in Type A are poorly-ordered kaolinite, illite, quartz, pyrite, and jarosite. Type B is mainly composed of well-ordered kaolinite, illite, siderite, ankerite, and calcite. Type C, with just one sample (JY-3-7c), which contains high proportions of calcite (54%) and ankerite (34%). Terrigenous minerals are elevated in coal plies that typically have relatively high contents of ash yield. The formation of syngenetic pyrite was generally due to seawater, while the sulphate minerals (jarosite and coquimbite) were derived from the oxidation of pyrite. Epigenetic vein-like or fracture-fillings carbonate minerals (ankerite, calcite, and siderite), kaolinite, and pyrite, as well as authigenic quartz were derived from the influx of hydrothermal fluids during different periods, from the authigenic to epigenetic. The paragonite in the coal may have been formed by the precipitated from Na-rich hydrothermal fluids. No effects of magmatic intrusion on mineralogy were investigated in this research. Full article

(This article belongs to the Collection Critical Metals and Minerals in Coal and Coal Combustion Products)

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25 pages, 11204 KiB

Open AccessFeature PaperArticle

Comparison of the Calcareous Shells of Belemnitida and Sepiida: Is the Cuttlebone Prong an Analogue of the Belemnite Rostrum Solidum?

by M. Isabel Benito and Matías Reolid

Minerals 2020, 10(8), 713; https://doi.org/10.3390/min10080713 - 12 Aug 2020

Cited by 4 | Viewed by 3950

Abstract

The microstructure of the rostrum solidum of Jurassic belemnites is compared with that of Sepia cuttlebones, in order to examine possible convergences in their style of growth. For this study, transmitted and polarized light, cathodoluminescence, epifluorescence, scanning electron and backscattered electron microscopy have [...] Read more.

The microstructure of the rostrum solidum of Jurassic belemnites is compared with that of Sepia cuttlebones, in order to examine possible convergences in their style of growth. For this study, transmitted and polarized light, cathodoluminescence, epifluorescence, scanning electron and backscattered electron microscopy have been employed. Despite differences in the primary mineralogy of the studied belemnites and sepiids, calcite and aragonite, respectively, many similarities have been observed between the microstructure of the belemnite rostra and the prong of Sepia cuttlebone: (1) In both, crystals start growing from successive spherulites, from which crystals emerge radially towards the apex and the external walls, displaying internally micro-fibrous texture. (2) Both display concentric growth layering, comprising an alternation of organic-rich and organic-poor layers, which, in turn, is traverse by the radially-arranged micro-fibrous crystals. (3) The highest organic matter content and porosity have been observed along the apical area of the Sepia prong, similarly to that interpreted for belemnite rostra. The strong convergences observed suggest that the growth of belemnites occurred similarly to that of the prong of sepiids and that the Sepia prong is the analog of the belemnite rostrum. Additionally, non-classical crystallization processes are proposed to be involved in the formation Sepia endoskeleton. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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9 pages, 1286 KiB

Open AccessArticle

Predicting the Logarithmic Distribution Factors for Coprecipitation into an Organic Salt: Selection of Rare Earths into a Mixed Oxalate

by Harry Watts and Yee-Kwong Leong

Minerals 2020, 10(8), 712; https://doi.org/10.3390/min10080712 - 12 Aug 2020

Cited by 2 | Viewed by 2365

Abstract

Thermodynamic modelling of a leaching system that involves concurrent precipitation depends on an understanding of how the metals distribute into the precipitate before an assessment of solubility can be made. It has been suggested in the past that a pair of rare earths [...] Read more.

Thermodynamic modelling of a leaching system that involves concurrent precipitation depends on an understanding of how the metals distribute into the precipitate before an assessment of solubility can be made. It has been suggested in the past that a pair of rare earths (A and B) in solution will separate from each other by oxalate precipitation according to a logarithmic distribution coefficient (

λ

), determined by the kinetics of the precipitation. By contrast, the present study hypothesises that

λ

may be approximated from thermodynamic terms, including the solubility product (K_Sp) of each rare earth oxalate and the stability constant (

β_{1})

for the mono-oxalato complex of each rare earth. The proposed model was used to calculate

λ

between pairs of rare earths. An experimental study was conducted to determine

λ

between selected pairs using homogenous precipitation through the hydrolysis of an oxalic acid ester, with fairly close agreement to the values under the proposed model. Though this model requires more thorough testing, as well as application to other organic salts, it may provide insight into distribution factors of a precipitate formed by a sequence of organic complexes. Full article

(This article belongs to the Special Issue Leaching of Rare Earth Elements from Various Sources)

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11 pages, 1284 KiB

Open AccessArticle

Removal of Pollutants from an AMD from a Coal Mine by Neutralization/Precipitation Followed by “In Vivo” Biosorption Step with the Microalgae Scenedesmus sp.

by Karine Batista dos Santos, Vítor Otacílio de Almeida, Jéssica Weiler and Ivo André Homrich Schneider

Minerals 2020, 10(8), 711; https://doi.org/10.3390/min10080711 - 12 Aug 2020

Cited by 12 | Viewed by 2785

Abstract

This work evaluates the benefits of a complementary treatment step of acid mine drainage (AMD) using the algae Scenedesmus sp. in terms of algae biomass production, residual metal removal, and the toxicity of the discharged water. Conventional treatment by neutralization/precipitation of an AMD [...] Read more.

This work evaluates the benefits of a complementary treatment step of acid mine drainage (AMD) using the algae Scenedesmus sp. in terms of algae biomass production, residual metal removal, and the toxicity of the discharged water. Conventional treatment by neutralization/precipitation of an AMD from a coal mine in Brazil was conducted with Ca(OH)₂ at pH 8.7. Algal growth studies were performed in the treated AMD, with and without a nutrient supply. The raw effluent and treatments were compared in terms of residual concentration of metals and sulfate, conductivity, and toxicity with the Allium cepa and Daphnia magna test organisms. The results show that the conventional treatment allowed a major metal removal, reduction in the conductivity, and good indices in the toxicological parameters evaluated. The biosorption with in vivo microalgae improved the quality of the effluent for residual metals. No significant toxicity was observed to Allium cepa in all treatments performed, while the Daphnia magna test indicated a reduction in toxicity after the biosorption step. It was concluded that algae growth can be carried out in treated mine waters, providing algae biomass and helping to achieve the standards for water discharge. Full article

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

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14 pages, 5603 KiB

Open AccessArticle

Development of a More Descriptive Particle Breakage Probability Model

by Murray M. Bwalya and Ngonidzashe Chimwani

Minerals 2020, 10(8), 710; https://doi.org/10.3390/min10080710 - 12 Aug 2020

Cited by 10 | Viewed by 2572

Abstract

Single-particle breakage test is becoming increasingly popular, as researchers seek to understand fracture response that is purely a function of the material being tested, instead of that which is based on the performance of the comminution device being used. To that end, an [...] Read more.

Single-particle breakage test is becoming increasingly popular, as researchers seek to understand fracture response that is purely a function of the material being tested, instead of that which is based on the performance of the comminution device being used. To that end, an empirical breakage probability model that builds on previous work was proposed. The experimental results demonstrate the significance of both energy input and the number of repeated breakage attempts. Four different materials were compared, to gain a better insight into the breakage response. This modelling work goes further from previous research of the authors, by showing that not only does size related threshold energy and repeated impacts characterize particle breakage properties, but each material exhibits unique trends in terms of how its threshold energy and its rate of deterioration varies with particle size and each impact, respectively. This behaviour can be attributed to the different mechanical characteristics of the material and their flaw distribution. The importance of these aspects was highlighted. Full article

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

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27 pages, 11481 KiB

Open AccessArticle

A Process Mineralogical Evaluation of Chromite at the Nkomati Nickel Mine, Uitkomst Complex, South Africa

by Thomas Dzvinamurungu, Derek Hugh Rose, Karel Stephanus Viljoen and Antoine Floribert Mulaba-Bafubiandi

Minerals 2020, 10(8), 709; https://doi.org/10.3390/min10080709 - 12 Aug 2020

Cited by 2 | Viewed by 3605

Abstract

A process mineralogical study based on three texturally and mineralogically different chromite-bearing ore types at the Nkomati nickel mine was undertaken, with focus on chromite. Chromite is a by-product of the Ni-Cu-Co-PGE ore at Nkomati Nickel mine. These being the PCMZ_MG (medium-grade Ni-Cu [...] Read more.

A process mineralogical study based on three texturally and mineralogically different chromite-bearing ore types at the Nkomati nickel mine was undertaken, with focus on chromite. Chromite is a by-product of the Ni-Cu-Co-PGE ore at Nkomati Nickel mine. These being the PCMZ_MG (medium-grade Ni-Cu sulphide silicate ore with disseminated chromite), PCMZ_HG (high-grade Ni-Cu sulphide silicate ore containing disseminated chromite) and MCHR (massive chromite unit) ore types. These were processed using benchtop flotation followed by gravity concentration using a shaking table at different grind sizes. Quantitative mineralogical data was obtained using a 600F Mineral Liberation Analyser for the unprocessed and processed ores at three selected target grinds. The Mineral Liberation Analyser data indicated that increased milling does not relate to increased chromite grades and recoveries, particularly for the disseminated PCMZ type ores based on laboratory-scale gravity concentration. The recovery is controlled largely by the chromite chemistry. The results also showed that the MCHR samples that underwent a pre-flotation stage before gravity separation had better Cr₂O₃ grades (45% to 47%) and recoveries (52% to 61%) than MCHR ore that did not undergo a pre-flotation stage, which recorded grades ranging from 44% to 46% and recoveries ranging from 43% to 60%. This holds promise for the blending of MCHR ores with the PCMZ ores. The PCMZ ores also displayed better Cr₂O₃ grades and recoveries at coarser grinds. The optimal target grind to process all three ore types is a P80 of 75 μm, which is the current grind size employed at Nkomati Nickel mine. Due to the low nickel price and grade the Nkomati Nickel mine is currently under care and maintenance. Full article

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

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14 pages, 6125 KiB

Open AccessArticle

Genesis of Two Types of Carbonaceous Material Associated with Gold Mineralization in the Bumo Deposit, Hainan Province, South China

by Zhengpeng Ding, Teng Deng, Deru Xu, Zenghua Li, Shaohao Zou, Lirong Li, Ke Xu, Yan Hai and Wen Ma

Minerals 2020, 10(8), 708; https://doi.org/10.3390/min10080708 - 10 Aug 2020

Cited by 9 | Viewed by 3399

Abstract

Carbonaceous material (CM) is common in meta-sediments and is generally interpreted to be intimately associated with gold mineralization. For the Bumo deposit in Hainan Province, South China, CM is mainly hosted by greenschist facies—to amphibolite-facies metamophic rocks of the Paleo—to the Mesoproterozoic Baoban [...] Read more.

Carbonaceous material (CM) is common in meta-sediments and is generally interpreted to be intimately associated with gold mineralization. For the Bumo deposit in Hainan Province, South China, CM is mainly hosted by greenschist facies—to amphibolite-facies metamophic rocks of the Paleo—to the Mesoproterozoic Baoban Group, and by auriferous veins which could be used as an important gold prospecting indicator. However, the genesis of CM and its relationship with gold mineralization are still unclear. From the field work and thin section observations two types of CM occur, i.e., layered and veinlet. The layered CM occurred in CM-bearing black shales, up to meters thick, and prevails in the deposit. More importantly, Au-bearing sulfides are commonly distributed along the boundary between the quartz veins and layered CM. In contrast, the veinlet CM, co-precipitated with native gold and sulfides, has the thickness of micro- to centi-meters, and these thin veins occur in quartz veins and hydrothermally altered rocks. In addition, layered CM has a stringy shape and laminate structure, while veinlet CM occurs as isometric particles based on the Scanning Electron Microscope (SEM) analysis. The Raman carbonaceous material geothermometer indicates that layered CM with a high maturity is formed at elevated temperatures of 400–550 °C, consistent with X-ray diffraction (XRD) analysis. In contrast, veinlet CM with a low maturity is formed at 200–350 °C and generally consistent with gold mineralization. In addition, layered CM has ^δ13C values ranging from −30 to −20%, demonstrating a biogenic origin. Consequently, it is interpreted that layered CM is formed by a pre-ore metamorphic event during Caledonian, and its reducing nature promotes gold precipitation via destabilization of aqueous Au complexes or facilitating sulfidation. Veinlet CM is of hydrothermal origin, and its precipitation modified the chemical conditions of ore fluids, leading to the destabilization of Au complexes, which therefore are favorable for mineralization. Full article

(This article belongs to the Special Issue Ore Genesis and Metamorphism: Geochemistry, Mineralogy, and Isotopes)

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21 pages, 6192 KiB

Open AccessArticle

Effectiveness of Fly Ash and Red Mud as Strategies for Sustainable Acid Mine Drainage Management

by Viktoria Keller, Srećko Stopić, Buhle Xakalashe, Yiqian Ma, Sehliselo Ndlovu, Brian Mwewa, Geoffrey S. Simate and Bernd Friedrich

Minerals 2020, 10(8), 707; https://doi.org/10.3390/min10080707 - 10 Aug 2020

Cited by 17 | Viewed by 3361

Abstract

Acid mine drainage (AMD), red mud (RM) and coal fly ash (CFA) are potential high environmental pollution problems due to their acidity, toxic metals and sulphate contents. Treatment of acidic mine water requires the generation of enough alkalinity to neutralize the excess acidity. [...] Read more.

Acid mine drainage (AMD), red mud (RM) and coal fly ash (CFA) are potential high environmental pollution problems due to their acidity, toxic metals and sulphate contents. Treatment of acidic mine water requires the generation of enough alkalinity to neutralize the excess acidity. Therefore, red mud types from Germany and Greece were chosen for the neutralization of AMD from South Africa, where this problem is notorious. Because of the high alkalinity, German red mud is the most promising precipitation agent achieving the highest pH-values. CFA is less efficient for a neutralization and precipitation process. An increase in temperature increases the adsorption kinetics. The maximum pH-value of 6.0 can be reached by the addition of 100 g German red mud at 20 °C to AMD-water with an initial pH value of 1.9. German red mud removes 99% of the aluminium as aluminium hydroxide at pH 5.0. The rare earth elements (yttrium and cerium) are adsorbed by Greek red mud with an efficiency of 50% and 80% at 60 °C in 5 min, respectively. Full article

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

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15 pages, 1666 KiB

Open AccessArticle

Considerations About Bi and Pb in the Crystal Structure of Cu-Bearing Tourmaline

by Andreas Ertl and Peter Bačík

Minerals 2020, 10(8), 706; https://doi.org/10.3390/min10080706 - 10 Aug 2020

Cited by 8 | Viewed by 2680

Abstract

Copper- and Mn-bearing elbaitic tourmaline (“Paraíba tourmaline”) sometimes contains significant amounts of Pb and Bi. Their position in the tourmaline crystal structure was studied with correlation analysis and bond valence calculations. Correlations between the F content and the X-site charge allow predicting the [...] Read more.

Copper- and Mn-bearing elbaitic tourmaline (“Paraíba tourmaline”) sometimes contains significant amounts of Pb and Bi. Their position in the tourmaline crystal structure was studied with correlation analysis and bond valence calculations. Correlations between the F content and the X-site charge allow predicting the X-site occupancy. Three sets of tourmaline analyses were studied: (1) Pb-rich tourmalines from the Minh Tien pegmatite, Vietnam; (2) Cu-, Pb- and Bi-bearing tourmalines from the Mulungu mine, Brazil; (3) Cu- and Bi-bearing tourmalines from the Alto dos Quintos mine, Brazil. Two correlations were plotted: (1) the charge by considering only Na¹⁺, Ca²⁺ and K¹⁺; (2) the charge by adding Pb²⁺ and Bi³⁺ to the X-site charge. When plotting correlations for the Minh Tien tourmalines, the correlation significantly improves by adding Pb²⁺ to the X site. For the Alto dos Quintos tourmalines, only a slight increase of the correlation coefficient is observed, while such a correlation for tourmalines from Mulungu interestingly shows a slight decrease of the correlation coefficient. Bond valence calculations revealed that Bi³⁺ and Pb²⁺ can indeed occupy the X site via BiLi(NaAl)_−1, PbLi(NaCu)₋₁ and possibly PbCu(NaAl)₋₁ substitutions as seen in the investigated tourmaline samples. At the Y site, Pb⁴⁺ can be substituted via PbLi(AlCu)₋₁, and Pb^VO(Al^VOH)₋₁, while Bi⁵⁺ does not have any stable arrangement in Cu-bearing fluor-elbaite. The occurrence of Pb⁴⁺ at the Y site could be one explanation for the results of the correlations of the Mulungu tourmalines. Another explanation could be that during the tourmaline crystallization some additional Bi and Pb came into the pegmatitic system and hence disturbed the correlation between the average X-site charge and the F content. Further plots of such correlations in “Paraíba tourmaline” samples might also help to distinguish between the worldwide localities of these rare and sought-after tourmalines. Full article

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

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19 pages, 7567 KiB

Open AccessArticle

Steel Slag Characterisation—Benefit of Coupling Chemical, Mineralogical and Magnetic Techniques

by Maud Herbelin, Jérôme Bascou, Véronique Lavastre, Damien Guillaume, Mhammed Benbakkar, Steve Peuble and Jean-Philippe Baron

Minerals 2020, 10(8), 705; https://doi.org/10.3390/min10080705 - 09 Aug 2020

Cited by 11 | Viewed by 4279

Abstract

Steel-making slag is largely used today in road construction and other applications, but significant volumes are landfilled and cannot be recycled for excessive contents in hazardous metals, such as chromium or vanadium. The long-term behaviour of this material is still little known, and [...] Read more.

Steel-making slag is largely used today in road construction and other applications, but significant volumes are landfilled and cannot be recycled for excessive contents in hazardous metals, such as chromium or vanadium. The long-term behaviour of this material is still little known, and the characterisation of large volume slag dumps remains an environmental challenge. In this study various analytical techniques are used to characterise Electric Arc Furnace (EAF) slag landfilled for several decades and exposed to chemical weathering and erosion. Coupling chemical, mineralogical and magnetic techniques helps to understand the relations between hazardous metals and mineral phases. A special interest is given to Fe-bearing minerals microstructure so as to link the magnetic properties of the material to its mineralogical composition. The studied slag presents high amounts of chromium (between 1 and 3 wt. %) and very high magnetic susceptibility values (near 60 × 10⁻⁶ m³/kg), explained by the presence of magnetite and a spinel solid solution. Some correlations are found between magnetic susceptibility and potentially hazardous metals, providing new perspectives for future environmental investigations. Full article

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19 pages, 2858 KiB

Open AccessArticle

Aboveground and Belowground Colonization of Vegetation on a 17-Year-Old Cover with Capillary Barrier Effect Built on a Boreal Mine Tailings Storage Facility

by Alex Proteau, Marie Guittonny, Bruno Bussière and Abdelkabir Maqsoud

Minerals 2020, 10(8), 704; https://doi.org/10.3390/min10080704 - 08 Aug 2020

Cited by 7 | Viewed by 2482

Abstract

Acid mine drainage is an important environmental risk linked to the surface storage of reactive mine tailings. To manage this problem, a cover with a capillary barrier effect (CCBE) can be used. This oxygen barrier cover relies on maintaining a fine-grained material layer [...] Read more.

Acid mine drainage is an important environmental risk linked to the surface storage of reactive mine tailings. To manage this problem, a cover with a capillary barrier effect (CCBE) can be used. This oxygen barrier cover relies on maintaining a fine-grained material layer (moisture-retaining layer, MRL) with a high degree of saturation. CCBEs can be colonized by surrounding plants. Plant roots pump water and could impact CCBE’s performance. This performance is predicted with unsaturated water flow numerical models in which vegetation parameters can be included. Vegetation parameters may be specific in a CCBE environment. Therefore, analyzing and quantifying the vegetation that colonizes this type of cover is necessary. Plant colonization was investigated through cover and density surveys on 12 transects on a 17-year-old CCBE in the mixed forest of Quebec, Canada. Then, aboveground vegetation and root colonization intensity at three depths in the MRL were characterized on 25 plots of five dominant vegetation types (Salix, Populus, Alnus, Picea sp., and herbaceous species). The mean root length density under plots dominated by Salix sp. was higher than in the other plots. Root colonization of the MRL was concentrated in the first 10 cm and occurred under all woody and herbaceous species as well. This work quantitatively describes, for the first time, the vegetation colonizing a CCBE both at the above- and belowground levels. These data will be useful to better predict the long-term performance of this engineered reclamation cover. Full article

(This article belongs to the Special Issue Biological Reclamation and Bio-Remediation of Former Mine Sites)

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12 pages, 3465 KiB

Open AccessArticle

Formation of Spessartine and CO₂ via Rhodochrosite Decarbonation along a Hot Subduction P-T Path

by Yuliya V. Bataleva, Aleksei N. Kruk, Ivan D. Novoselov and Yuri N. Palyanov

Minerals 2020, 10(8), 703; https://doi.org/10.3390/min10080703 - 07 Aug 2020

Cited by 3 | Viewed by 2379

Abstract

Experimental simulation of rhodochrosite-involving decarbonation reactions resulting in the formation of spessartine and CO₂-fluid was performed in a wide range of pressures (P) and temperatures (T) corresponding to a hot subduction P-T path. Experiments were [...] Read more.

Experimental simulation of rhodochrosite-involving decarbonation reactions resulting in the formation of spessartine and CO₂-fluid was performed in a wide range of pressures (P) and temperatures (T) corresponding to a hot subduction P-T path. Experiments were carried out using a multi-anvil high-pressure apparatus of a “split-sphere” type (BARS) in an MnCO₃–SiO₂–Al₂O₃ system (3.0–7.5 GPa, 850–1250 °C and 40–100 h.) with a specially designed high-pressure hematite buffered cell. It was experimentally demonstrated that decarbonation in the MnCO₃–SiO₂–Al₂O₃ system occurred at 870 ± 20 °C (3.0 GPa), 1070 ± 20 °C (6.3 GPa), and 1170 ± 20 °C (7.5 GPa). Main Raman spectroscopic modes of the synthesized spessartine were 349–350 (R), 552(υ₂), and 906–907 (υ₁) cm⁻¹. As evidenced by mass spectrometry (IRMS) analysis, the fluid composition corresponded to pure CO₂. It has been experimentally shown that rhodochrosite consumption to form spessartine + CO₂ can occur at conditions close to those of a hot subduction P-T path but are 300–350 °C lower than pyrope + CO₂ formation parameters at constant pressures. We suppose that the presence of rhodocrosite in the subducting slab, even as solid solution with Mg,Ca-carbonates, would result in a decrease of the decarbonation temperatures. Rhodochrosite decarbonation is an important reaction to explain the relationship between Mn-rich garnets and diamonds with subduction/crustal isotopic signature. Full article

(This article belongs to the Special Issue Behaviour of Volatiles and Fluid-Mobile Elements in Subduction Zones)

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23 pages, 22182 KiB

Open AccessArticle

Fedorite from Murun Alkaline Complex (Russia): Spectroscopy and Crystal Chemical Features

by Ekaterina V. Kaneva, Roman Yu. Shendrik, Tatiana A. Radomskaya and Ludmila F. Suvorova

Minerals 2020, 10(8), 702; https://doi.org/10.3390/min10080702 - 07 Aug 2020

Cited by 11 | Viewed by 3932

Abstract

Fedorite is a rare phyllosilicate, having a crystal structure characterized by SiO₄-tetrahedral double layers located between continuous layers formed by edge-sharing (Ca,Na)-octahedra, and containing interlayer K, Na atoms and H₂O molecules. A mineralogical-petrographic and detailed crystal-chemical study of fedorite [...] Read more.

Fedorite is a rare phyllosilicate, having a crystal structure characterized by SiO₄-tetrahedral double layers located between continuous layers formed by edge-sharing (Ca,Na)-octahedra, and containing interlayer K, Na atoms and H₂O molecules. A mineralogical-petrographic and detailed crystal-chemical study of fedorite specimens from three districts of the Murun alkaline complex was performed. The sequence of the crystallization of minerals in association with fedorite was established. The studied fedorite samples differ in the content of interlayer potassium and water molecules. A comparative analysis based on polyhedral characteristics and deformation parameters was carried out. For the first time, EPR, optical absorption and emission spectra were obtained for fedorite. The raspberry-red coloration of the mineral specimens could be attributed to the presence of Mn⁴⁺ ions. Full article

(This article belongs to the Special Issue Layered Minerals and Materials: Crystal Structures, Properties and Applications)

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12 pages, 5432 KiB

Open AccessArticle

The Effect of Alkali Roasting Pretreatment on Nickel Extraction from Limonite Ore by Using Dissolved SO₂-Air

by Winny Wulandari, Meiyer Marthen Kinda, Rahmaditha Murida and Tjokorde Walmiki Samadhi

Minerals 2020, 10(8), 701; https://doi.org/10.3390/min10080701 - 07 Aug 2020

Cited by 2 | Viewed by 3178

Abstract

Extraction of limonite ore using dissolved SO₂–air is an alternative hydrometallurgical method for nickel recovery. This process is carried out at atmospheric pressure and is shown to have good selectivity of nickel over iron, but with a low recovery yield. The [...] Read more.

Extraction of limonite ore using dissolved SO₂–air is an alternative hydrometallurgical method for nickel recovery. This process is carried out at atmospheric pressure and is shown to have good selectivity of nickel over iron, but with a low recovery yield. The literature refers to the application of alkali roasting as pretreatment in laterite ore leaching to increase nickel recovery. Thus, this study aims to apply the combination method of alkali roasting and leaching to extract nickel from limonite ore (1.33% Ni, 46.61% Fe) from the Southeast Sulawesi region. Three alkali compounds were included in the study (NaOH, Na₂CO₃ and Na₂SO₄). The batch-leaching process was carried out at pH 1 and 3 and temperatures of 55 and 80

°

C for 180 min. The leach liquors were sampled at 15, 60, 90 and 120 min, and concentrations of the extracted metals were measured by Atomic Absorption Spectrometry (AAS). A mineralogy characterization of the raw ore and its residue after leaching was undertaken by using X-Ray Diffraction (XRD), while the thermal decomposition behavior of the ore was characterized by Thermogravimetry Analyzer (TGA)/Differential Scanning Calorimetry (DSC). The addition of Na₂CO₃, Na₂SO₄ and NaOH in the ore pretreatment increases nickel recovery from 14.80% without alkali roasting to 23.99%, 28.15% and 39.22%, respectively. The optimum extraction condition for nickel recovery is at pH 1 and a temperature of 80

°

C. However, the highest Ni/Fe selectivity of 24,947 is obtained at pH 3 and a temperature of 80

°

C, preceded by roasting in the absence of alkali. Compared to other hydrometallurgical processes, the process studied in this work exhibits lower recovery, but provides an alternative to extract nickel from low-grade limonite ore. Full article

(This article belongs to the Special Issue The Processing of Alternative and Urban Ores)

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11 pages, 3186 KiB

Open AccessArticle

Composition and Technological Properties of Clays for Structural Ceramics in Limpopo (South Africa)

by Lawrence Diko-Makia and Rofhiwa Ligege

Minerals 2020, 10(8), 700; https://doi.org/10.3390/min10080700 - 07 Aug 2020

Cited by 7 | Viewed by 3576

Abstract

This study evaluated the potential of raw clays from the Mukondeni region for structural ceramics and pottery based on traditional firing techniques. Physical properties were identified by particle size distribution, consistency limits, and clay activity. Mineralogical and chemical properties were investigated by X-ray [...] Read more.

This study evaluated the potential of raw clays from the Mukondeni region for structural ceramics and pottery based on traditional firing techniques. Physical properties were identified by particle size distribution, consistency limits, and clay activity. Mineralogical and chemical properties were investigated by X-ray diffraction (XRD) and X-ray fluorescence (XRF). Extruded clay bodies were fired at 900 °C. Technological characteristics were measured by weight loss (WL), bulk density (BD), dry linear shrinkage (DLS), fired linear shrinkage (FLS), water absorption (WA), and flexural strength (FS). The clays were low in <2 µm fractions (≤19%) and of medium to high plasticity with a clayey silt texture. Smectite was the dominant clay mineral while quartz and feldspar were major non clay minerals. The most abundant oxides were SiO₂ (63.57–68.73%), Al₂O₃ (13.9–15.61%), and Fe₂O₃ (4.86–6.18%), whereas K₂O, CaO, MgO, Na₂O, TiO₂, and P₂O₅ were depleted. Characterization based on the clay workability chart, Winkler’s diagram, and compositional ternary diagrams revealed acceptable extrusion properties and suitability for structural ceramics and earthenware. The clays showed acceptable WL, BD, LS, and WA, but unsatisfactory FS (≤1.08 MPa). Low mechanical strength was attributed to presence of smectites and inert nature of feldspar at 900 °C. Beneficiation through mixing with carbonate-rich raw materials is recommended. Full article

(This article belongs to the Special Issue Industrial Minerals)

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18 pages, 21814 KiB

Open AccessArticle

Microstructure Investigation of Oil-Bearing Rhyolites: A Case Study from the Hailar Basin, NE China

by Anqi Mao, Han Zheng and Xiaomeng Sun

Minerals 2020, 10(8), 699; https://doi.org/10.3390/min10080699 - 06 Aug 2020

Cited by 3 | Viewed by 3007

Abstract

Understanding the microstructure of rhyolites may greatly promote exploration efforts on rhyolitic hydrocarbon reservoirs; however, related studies are sparse. In this contribution, the microstructure and related porosity of oil-bearing rhyolitic lavas from the Hailar Basin (NE China) were investigated using a combination of [...] Read more.

Understanding the microstructure of rhyolites may greatly promote exploration efforts on rhyolitic hydrocarbon reservoirs; however, related studies are sparse. In this contribution, the microstructure and related porosity of oil-bearing rhyolitic lavas from the Hailar Basin (NE China) were investigated using a combination of optical microscopy, fluorescence image analysis, and scanning electron microscopy. The direct visual and quantitative analyses show that the rhyolites are heterogeneous and porous rocks and have complex microstructures. Phenocryst-rich rhyolitic lava, perlitic lava, and spherulitic rhyolite may be favorable targets for rhyolitic hydrocarbon exploration. For the phenocryst-rich rhyolitic lavas, embayment pores, cleavages, cavitational and shear fractures, and intracrystalline sieve pores are commonly observed in the phenocrysts; while flow-parallel laminar and micropores are ubiquitous in the groundmass. Perlitic lavas are characterized by the occurrence of numerous perlitic fractures which can also be produced in the glassy groundmass of other lavas. Spherulitic rhyolites mainly consist of small-sized (<1 mm) clustered or large-sized (>1 mm) isolated spherulites. Clustered spherulites are characterized by the development of interspherulite pores. Isolated spherulites contain numerous radiating micropores. Both types of spherulites may have water expulsion pores formed in the spherulite–glass border. The formation of the microstructure and related porosity of rhyolites is controlled by pre-, syn- (e.g., deuteric crystal dissolution, cavitation, ductile–brittle deformation, and high-T devitrification), and post-volcanic (e.g., hydration and low-T devitrification) processes. Although pores with diameters > 50 μm are often observed, small pores dominate in pore-size distribution. Small (<15 μm) and large (>300 μm) pores give the most volumetric contribution in most cases. Medium-sized pores with diameters ranging from ~150–300 μm are the least developed and contribute the least to the total volume. The results of this paper can be beneficial to further the understanding of the microstructure and pore system of rhyolites and may be applied to rhyolitic lava hydrocarbon reservoirs elsewhere. Full article

(This article belongs to the Special Issue Microtexture Characterization of Rocks and Minerals)

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16 pages, 6700 KiB

Open AccessArticle

Epithermal Mineralization in the Busang Southeast Zone, Indonesia: New Insight into the Au Prospect at the Center of the Bre-X Fraud

by Evan Slater, Jacob Hanley, Thomas Mulja, Marcos Zentilli and Corwin Trottier

Minerals 2020, 10(8), 698; https://doi.org/10.3390/min10080698 - 06 Aug 2020

Viewed by 4551

Abstract

The Busang mineral prospect in Kalimantan, Indonesia, was reported to host a large Au resource until 1997 when it was revealed that drill core samples had been deliberately and systematically contaminated (“salted”) with extraneous Au to falsify resource estimates. One month before the [...] Read more.

The Busang mineral prospect in Kalimantan, Indonesia, was reported to host a large Au resource until 1997 when it was revealed that drill core samples had been deliberately and systematically contaminated (“salted”) with extraneous Au to falsify resource estimates. One month before the fraud was uncovered, Dr. G. Milligan, then professor emeritus of geology, visited the site to collect a suite of core samples for academic study that was deemed representative of the host rocks, alteration, and mineralization of the Busang Southeast Zone. These samples were re-examined here by optical microscopy, electron microprobe (EMPA), whole-rock geochemistry, and fluid inclusion microthermometry to characterize the subsurface geology and hydrothermal mineralization, and to assess reasons why the system is of uneconomic character. The host rocks were variably altered calc-alkaline porphyritic subvolcanic diorites, typical of the lithological units along the mineralized trend in the Kalimantan Gold Belt. Early hydrothermal mineralization with quartz-sulfide (pyrite, chalcopyrite, Cu-sulfosalts) stockwork veinlets associated with pervasive phyllic and propylitic alteration was overprinted by crudely banded quartz-carbonate-sulfide/sulfosalt (pyrite, sphalerite, chalcopyrite, galena, tennantite-tetrahedrite, bournonite-seligmannite) veins. The stockwork veins were associated with up to 140 ppb bulk rock Au, some of which was hosted by Cu-sulfosalts. Microthermometry on quartz-hosted aqueous fluid inclusion assemblages (FIA; n = 13) and single inclusions (non-FIA; n = 20) in quartz-carbonate-sulfide/sulfosalt veins yielded an overall range in homogenization temperatures (T_h) between 179 °C and 366 °C and bulk salinities between 1.1 wt.% to 8.6 wt.% NaCl equivalent, with much smaller data ranges for individual FIA (e.g., FIA 3; 239.1 °C to 240.5 °C and 0.5 wt.% to 1.4 wt.% NaCl equivalent). Primary FIA along growth zones in quartz were identified, providing constraints on fluid characteristics at the time of quartz growth. Carbonate-hosted FIA (n = 3) and single inclusions (non-FIA; n = 3) in the same veins yielded T_h between 254 °C and 343 °C and bulk salinities of 1.1 wt.% to 11.6 wt.% NaCl equivalent. Likewise, data ranges for individual FIA were much smaller. Many of the geological characteristics of the Busang Southeast Zone were compatible with a telescoped, intermediate-sulfidation epithermal system, having formed from diluted magmatic fluids that precipitated weak base metal mineralization. However, the system was unproductive with respect to Au and Ag, at least within the studied area. Of note, vein textures and fluid inclusion characteristics indicative of boiling or efficient fluid mixing—processes both considered critical for the formation of economic lode gold deposits—were absent in the samples. Full article

(This article belongs to the Section Mineral Deposits)

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