Microanalysis Applied to Mineral Deposits

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: closed (1 April 2024) | Viewed by 3757

Special Issue Editors

Division of Geosciences and Environmental Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden
Interests: trace element ore genesis; carbon capture and storage; mineral carbonation; mineralogy; mineral chemistry; microanalysis

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Guest Editor
Circular Economy Solutions Unit, Circular Raw Materials Hub, Geological Survey of Finland, F1-02151 Espoo, Finland
Interests: geoanalytical techniques; battery minerals
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Special Issue Information

Dear Colleagues,

Societal demand for minerals and metals is increasing, and so-called critical raw materials (CRMs) have lately received much focus. Parallel to this increase, sustainability in the metal supply chain is a growing concern for the public, and the environmental legislation for mining activities has become much stricter in many countries. Since CRMs typically occur as low concentration by-products in ores, more in-depth microanalytical studies of the complex elemental composition of ore deposits are required to enable the optimization of existing mining operations, as larger portions of ore bodies can be recovered.

Some metals may have economic by-products. Others are deleterious to the environment or impair the recovery of the main metal commodity. Hence, detailed mineralogical, textural and geochemical knowledge of an ore body is crucial to maximize both the extraction and sustainability of a mining operation.

The purpose of this Special Issue, “Microanalysis applied to mineral deposits”, is to publish recent research that shows the value and range of microanalytical studies of ore deposits.

Dr. Glenn Bark
Prof. Dr. Alan R. Butcher
Guest Editors

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Keywords

  • ore deposits
  • ore mineralogy
  • critical raw materials
  • by-products
  • microanalysis

Published Papers (3 papers)

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Research

22 pages, 7342 KiB  
Article
Computed Tomography of Scheelite Ore, Kara, Australia: Morphological Characterisation and Modal Mineralogy
by Leonard T. Krebbers, Julie A. Hunt and Bernd G. Lottermoser
Minerals 2024, 14(4), 345; https://doi.org/10.3390/min14040345 - 27 Mar 2024
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Abstract
Metal ores are mineralogically characterised to understand their genesis in order to allow informed decisions on mineral processing and to recognise likely environmental risks upon mining. However, standard mineralogical techniques generate only two-dimensional information at best, which in addition may be subject to [...] Read more.
Metal ores are mineralogically characterised to understand their genesis in order to allow informed decisions on mineral processing and to recognise likely environmental risks upon mining. However, standard mineralogical techniques generate only two-dimensional information at best, which in addition may be subject to sampling and stereological errors. By contrast, computed tomography (CT) is a non-destructive imaging technique that allows three-dimensional analysis of solid materials. In the present study, two ore types of the Kara Fe-W deposit (Australia) were characterised using CT to examine their mineral texture and modal mineralogy as well as scheelite distribution and ore grade (WO3). The results show that scheelite is primarily associated with hydrous phases (e.g., epidote, chlorite, amphibole) and occurs as massive or disseminated mineral as well as vein-fill at minor and trace concentrations. This study demonstrates that CT of scheelite ore enables accurate 3D texture visualisation (volume, grain size distribution) and yields valid quantitative data on modal mineralogy and WO3 grade of individual ore samples. Consequently, CT analysis of scheelite-bearing ore provides information relevant for ore genesis studies and comminution strategies for the possible recovery of scheelite as a by-product from metalliferous ores. Full article
(This article belongs to the Special Issue Microanalysis Applied to Mineral Deposits)
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28 pages, 7482 KiB  
Article
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
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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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30 pages, 13354 KiB  
Article
Gold and Arsenic in Pyrite and Marcasite: Hydrothermal Experiment and Implications to Natural Ore-Stage Sulfides
by Elena V. Kovalchuk, Boris R. Tagirov, Sergei E. Borisovsky, Maximilian S. Nickolsky, Evgeniya E. Tyukova, Nina V. Sidorova, Vladimir B. Komarov, Anna A. Mezhueva, Vsevolod Yu. Prokofiev and Ilya V. Vikentyev
Minerals 2024, 14(2), 170; https://doi.org/10.3390/min14020170 - 4 Feb 2024
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Abstract
Hydrothermal synthesis experiments were performed in order to quantify the states of Au and As in pyrite and marcasite. The experiments were performed at 350 °C/500 bar and 490 °C/1000 bar (pyrite–pyrrhotite buffer, C(NaCl) = 15 and 35 wt.%). The synthesis products [...] Read more.
Hydrothermal synthesis experiments were performed in order to quantify the states of Au and As in pyrite and marcasite. The experiments were performed at 350 °C/500 bar and 490 °C/1000 bar (pyrite–pyrrhotite buffer, C(NaCl) = 15 and 35 wt.%). The synthesis products were studied by EPMA, LA-ICP-MS, and EBSD. The EPMA was applied for simultaneous determinations of Au, As, Fe, and S, with a Au detection limit of 45–48 ppm (3σ). The analyses were performed along profiles across zonal grains. The concentrations of As and Au up to 5 wt.% and 8000 ppm, respectively, were determined in pyrite and up to 6 wt.% and 1300 ppm in marcasite. In pyrite, the Au concentration decreases with fluid salinity and temperature increases. Strong positive Au–As correlation and strong negative Au–Fe and As–S correlation were identified in pyrite. Comparison of the correlations with theoretical lines implies Au–As clustering. The cluster stoichiometry is inferred to be [AuAs10]. Most probably, As in pyrite presents in the form of clusters and in the As→S solid solution. Incorporation of Au in As-rich pyrite can be controlled by the reductive deposition mechanism. In marcasite, the concentrations of Au are not correlated with the As content. The [AuAs10] clusters enrich the {210}, {113}, and {111} pyrite faces, where the former exhibits the highest affinity to Au and As. The affinity of {110} and {100} forms to Au and As is lower. Implication of the experimental results to data for natural auriferous pyrite shows that the increase of Au content at C(As) > 0.5–1 wt.% is caused by the incorporation of the Au-As clusters, but not because of the formation of Au→Fe solid solution. Therefore, the concentration of “invisible” gold in pyrite is dictated solely by the hydrothermal fluid chemistry and subsequent ore transformations. Full article
(This article belongs to the Special Issue Microanalysis Applied to Mineral Deposits)
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