Application of HPGR and X-Ray CT to investigate the potential of Witwatersrand gold ore for heap leaching : a process mineralogy approach

Includes bibliographical references.Auriferous conglomerates of the Archaean Witwatersrand Basin in South Africa host one of the largest known gold resources and rate as the world’s most outstanding example of a fossil megaplacer deposit. For the past 40 years, Witwatersrand gold production in South Africa has been progressively declining due to problems related to high energy costs, decreasing grade, accessibility to greater depths, health and safety issues, labour union unrest and economic uncertainties: thus the overall viability of current gold production is questionable. Ultimately, the future of Witwatersrand gold mining relies on devising smarter strategies across the entire industry, but in particular critical areas such as comminution and extraction. With the continuous increase in mining depth, dominance of low-grade gold ores and strict safety regulations, metallurgical processing options have become limited. Heap leaching is a well-established technology which continues to grow in use and provides several benefits to solve some of these problems. High pressure grinding rolls (HPGR) is another technology with significant potential, especially for its application in coarse particle heap leaching due to its ability to induce micro-cracks as well as its high grinding efficiency and low energy requirements. This study explores the use of these two technologies in a process mineralogical framework using novel 3D X-ray computed tomography mineralogical analysis in order to assess a potential of the Witwatersrand gold ore for heap leaching

Emerging criticality: Unraveling shifting dynamics of the EU's critical raw materials and their implications on Canada and South Africa

Critical Raw Materials (or CRMs) are materials that are in high demand, difficult to replace and whose supply is prone to disruption. Various nations have defined CRM lists, although terminology, supporting data and assessment frameworks differ. The European Union (EU) has the longest published history of CRM lists with the first one published in 2011, followed by 3-year revisions. In this study, we analyze CRM designation trends over time by using the EU's five CRM lists to deduce the driving factors. Overall, the number of CRMs have increased by 1.67 new CRMs per year from 2011 to 2023, with the number of new CRMs yet to reach a plateau. Our analysis also reveals issues that could affect the value of the CRM lists including: (1) a hidden two-stage process with transparency issues; (2) static baselines with regards to criticality; (3) an overemphasis on ideology versus pragmatism; (4) a lack of differentiation between CRMs and strategic raw materials (SRMs); (5) a lack of foresight; and (6) a lack of consideration for extrinsic risks and system behaviour. Given these issues, we provide suggestions to improve the CRM assessment methodology and discuss the implications for the EU and the minerals industry. Subsequently, we extend our findings to Canada and South Africa, which are nations in the early stages of CRM framework creation. We find that Canada has more time to realize its CRM framework as compared to the EU, and that South Africa may be faced with a bifurcating reality of extra-national and national needs. Our findings also highlight serious geopolitical implications with the ensuing competition for resources likely resulting in the formation of economic blocs, clubs or cartels. Finally, improvements to the methodology resulting in more predictable outcomes would better incentivize the minerals industry to lower investment risk and ensure a smooth and pragmatic green energy transition

Predictive Geochemical Exploration: Inferential Generation of Modern Geochemical Data, Anomaly Detection and Application to Northern Manitoba

Geochemical surveys contain an implicit data lifecycle or pipeline that consists of data generation (e.g., sampling and analysis), data management (e.g., quality assurance and control, curation, provisioning and stewardship) and data usage (e.g., mapping, modeling and hypothesis testing). The current integration of predictive analytics (e.g., artificial intelligence, machine learning, data modeling) into the geochemical survey data pipeline occurs almost entirely within the data usage stage. In this study, we predict elemental concentrations at the data generation stage and explore how predictive analytics can be integrated more thoroughly across the data lifecycle. Inferential data generation is used to modernize lake sediment geochemical data from northern Manitoba (Canada), with results and interpretations focused on elements that are included in the Canadian Critical Minerals list. The results are mapped, interpreted and used for downstream analysis through geochemical anomaly detection to locate further exploration targets. Our integration is novel because predictive modeling is integrated into the data generation and usage stages to increase the efficacy of geochemical surveys. The results further demonstrate how legacy geochemical data are a significant data asset that can be predictively modernized and used to support time-sensitive mineral exploration of critical minerals that were unanalyzed in original survey designs. In addition, this type of integration immediately creates the possibility of a new exploration framework, which we call predictive geochemical exploration. In effect, it eschews sequential, grid-based and fixed resolution sampling toward data-driven, multi-scale and more agile approaches. A key outcome is a natural categorization scheme of uncertainty associated with further survey or exploration targets, whether they are covered by existing training data in a spatial or multivariate sense or solely within the coverage of inferred secondary data. The uncertainty categorization creates an effective implementation pathway for future multi-scale exploration by focusing data generation activities to de-risk survey practices

Big geochemical data through remote sensing for dynamic mineral resource monitoring in tailing storage facilities

Evolution in geoscientific data provides the mineral industry with new opportunities. A direction of geochemical data generation evolution is towards big data to meet the demands of data-driven usage scenarios that rely on data velocity. This direction is more significant where traditional geochemical data are not ideal, which is the case for evaluating unconventional resources, such as tailing storage facilities (TSFs), because they are not static due to sedimentation, compaction and changes associated with hydrospheric and lithospheric processes (e.g., erosion, saltation and mobility of chemical constituents). In this paper, we generate big secondary geochemical data derived from Sentinel-2 satellite-remote sensing data to showcase the benefits of big geochemical data using TSFs from the Witwatersrand Basin (South Africa). Using spatially fused remote sensing and legacy geochemical data on the Dump 20 TSF, we trained a machine learning model to predict in-situ gold grades. Subsequently, we deployed the model to the Lindum TSF, which is 3 km away, over a period of a few years (2015-2019). We were able to visualize and analyze the temporal variation in the spatial distributions of the gold grade of the Lindum TSF. Additionally, we were able to infer extraction sequencing (to the resolution of the data), acid mine drainage formation and seasonal migration. These findings suggest that dynamic mineral resource models and live geochemical monitoring (e.g., of elemental mobility and structural changes) are possible without additional physical sampling

Geochemistry of Palaeoarchaean to Palaeoproterozoic Kaapvaal Craton Marine Shales: Implications for Sediment Provenance and Siderophile Elements Endowment

The Kaapvaal Craton hosts a number of large gold deposits (e.g. Witwatersrand Supergroup) which mining companies have exploited at certain stratigraphic positions. It also hosts the largest platinum group element (PGE) deposits (e.g. Bushveld Igneous Complex) which mining companies have exploited in different mineralised layered magmatic zones. In spite of the extensive exploration history in the Kaapvaal Craton, the origin of the Witwatersrand gold deposits and Bushveld Igneous Complex PGE deposits has remained one of the most debated topics in economic geology. The goal of this study was to identify the geochemical characteristics of marine shales in the Barberton, Witwatersrand, and Transvaal supergroups in South Africa in order to make inferences on their sediment provenance and siderophile element endowments. Understanding why some of the Archaean and Proterozoic hinterlands are heavily mineralised, compared to others with similar geological characteristics, will aid in the development of more efficient exploration models. Fresh, unmineralised marine shales from the Barberton (Fig Tree and Moodies groups), Witwatersrand (West Rand and Central Rand groups), and Transvaal (Black Reef Formation and Pretoria Group) supergroups were sampled from drill core and underground mining exposures. Analytical methods, such as X-ray powder diffraction (XRD), optical microscopy, X-ray fluorescence (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and electron microprobe analysis (EMPA) were applied to comprehensively characterise the shales. All of the Au and PGE assays examined the newly collected shale samples. The Barberton Supergroup shales consist mainly of quartz, illite, chlorite, and albite, with diverse heavy minerals, including sulfides and oxides, representing the minor constituents. The regionally persistent Witwatersrand Supergroup shales consist mainly of quartz, muscovite, and chlorite, and also contain minor constituents of sulfides and oxides. The Transvaal Supergroup shales comprise quartz, chlorite, and carbonaceous material. Major, trace (including rare-earth element) concentrations were determined for shales from the above supergroups to constrain their source and post-depositional evolution. Chemical variations were observed in all the studied marine shales. Results obtained from this study revealed that post-depositional modification of shale chemistry was significant only near contacts with over- and underlying coarser-grained siliciclastic rocks and along cross-cutting faults, veins, and dykes. Away from such zones, the shale composition remained largely unaltered and can be used to draw inferences concerning sediment provenance and palaeoweathering in the source region and/or on intrabasinal erosion surfaces. Evaluation of weathering profiles through sections of the studied supergroups revealed that the shales therein are characterised by high chemical index of alteration (CIA), chemical index of weathering (CIW), and index of compositional variability (ICV), suggesting that the source area was lithologically complex and subject to intense chemical weathering. A progressive change in the chemical composition was identified, from a dominant ultramafic–mafic source for the Fig Tree Group to a progressively felsic–plutonic provenance for the Moodies Group. The West Rand Group of the Witwatersrand Supergroup shows a dominance of tonalite–trondhjemite–granodiorite and calcalkaline granite sources. Compositional profiles through the only major marine shale unit within the Central Rand Group indicate the progressive unroofing of a granitic source in an otherwise greenstone-dominated hinterland during the course of sedimentation. No plausible likely tectonic setting was obtained through geochemical modelling. However, the combination of the systematic shale chemistry, geochronology, and sedimentology in the Witwatersrand Supergroup supports the hypothesised passive margin setting for the >2.98 to 2.91 Ga West Rand Group, and an active continental margin source for the overlying >2.90 to 2.78 Ga Central Rand Group, along with a foreland basin setting for the latter. Ultra-low detection limit analyses of gold and PGE concentrations revealed a variable degree of gold accumulation within pristine unmineralised shales. All the studied shales contain elevated gold and PGE contents relative to the upper continental crust, with marine shales from the Central Rand Group showing the highest Au (±9.85 ppb) enrichment. Based on this variation in the provenance of contemporaneous sediments in different parts of the Kaapvaal Craton, one can infer that the siderophile elements were sourced from a fertile hinterland, but concentrated into the marine shales by a combination of different processes. It is proposed that accumulation of siderophile elements in the studied marine shales was mainly controlled by mechanical coagulation and aggregation. These processes involved suspended sediments, fine gold particles, and other trace elements being trapped in marine environments. Mechanical coagulation and aggregation resulted in gold enrichments by 2–3 orders of magnitude, whereas some of the gold in these marine shales can be reconciled by seawater adsorption into sedimentary pyrite. For the source of gold and PGEs in the studied marine shales in the Kaapvaal Craton, a genetic model is proposed that involves the following: (1) A highly siderophile elements enriched upper mantle domain, herein referred to as “geochemically anomalous mantle domain”, from which the Kaapvaal crust was sourced. This mantle domain enriched in highly siderophile elements was formed either by inhomogeneous mixing with cosmic material that was added during intense meteorite bombardment of the Hadaean to Palaeoarchaean Earth or by plume-like ascent of relics from the core–mantle boundary. In both cases, elevated siderophile elements concentrations would be expected. The geochemically anomalous mantle domain is likely the ultimate source of the Witwatersrand modified palaeoplacer gold deposits and was tapped again ca. 2.054 Ga during the emplacement of the Bushveld Igneous Complex. Therefore, I propose that there is a genetic link (i.e. common geochemically anomalous mantle source) between the Witwatersrand gold deposits and the younger Bushveld Igneous Complex PGE deposits. (2) Scavenging of crustal gold by various surface processes such as trapping of gold from Archaean/Palaeoproterozoic river water on the surface of local photosynthesizing cyanobacterial or microbial mats, and reworking of these mats into erosion channels during flooding events. The above two models complement each other, with model (1) providing a common geological source for the Witwatersrand gold and Bushveld Igneous Complex PGE deposits, and model (2) explaining the processes responsible for Witwatersrand-type gold pre-concentration processes. In sequences such as the Transvaal Supergroup, a less fertile hinterland and/or less reworking of older sediments led to a correspondingly lower gold endowment. These findings indicate temporal distribution of siderophile elements in the upper crust (e.g. marine shales). The overall implications of these findings are that background concentrations of gold and PGEs can be used to target potential exploration areas in other cratons of similar age. This increases the likelihood of finding other Witwatersrand-type gold or Bushveld Igneous Complex-type PGE deposits in other cratons

Geochemie paläoarchaischer bis paläoproterozoischer mariner Tonschiefer des Kaapvaal Kratons: Hinweise auf Sediment Provenienz und Anreicherung an siderophilen Elementen

The Kaapvaal Craton hosts a number of large gold deposits (e.g. Witwatersrand Supergroup) which mining companies have exploited at certain stratigraphic positions. It also hosts the largest platinum group element (PGE) deposits (e.g. Bushveld Igneous Complex) which mining companies have exploited in different mineralised layered magmatic zones. In spite of the extensive exploration history in the Kaapvaal Craton, the origin of the Witwatersrand gold deposits and Bushveld Igneous Complex PGE deposits has remained one of the most debated topics in economic geology. The goal of this study was to identify the geochemical characteristics of marine shales in the Barberton, Witwatersrand, and Transvaal supergroups in South Africa in order to make inferences on their sediment provenance and siderophile element endowments. Understanding why some of the Archaean and Proterozoic hinterlands are heavily mineralised, compared to others with similar geological characteristics, will aid in the development of more efficient exploration models. Fresh, unmineralised marine shales from the Barberton (Fig Tree and Moodies groups), Witwatersrand (West Rand and Central Rand groups), and Transvaal (Black Reef Formation and Pretoria Group) supergroups were sampled from drill core and underground mining exposures. Analytical methods, such as X-ray powder diffraction (XRD), optical microscopy, X-ray fluorescence (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and electron microprobe analysis (EMPA) were applied to comprehensively characterise the shales. All of the Au and PGE assays examined the newly collected shale samples. The Barberton Supergroup shales consist mainly of quartz, illite, chlorite, and albite, with diverse heavy minerals, including sulfides and oxides, representing the minor constituents. The regionally persistent Witwatersrand Supergroup shales consist mainly of quartz, muscovite, and chlorite, and also contain minor constituents of sulfides and oxides. The Transvaal Supergroup shales comprise quartz, chlorite, and carbonaceous material. Major, trace (including rare-earth element) concentrations were determined for shales from the above supergroups to constrain their source and post-depositional evolution. Chemical variations were observed in all the studied marine shales. Results obtained from this study revealed that post-depositional modification of shale chemistry was significant only near contacts with over- and underlying coarser-grained siliciclastic rocks and along cross-cutting faults, veins, and dykes. Away from such zones, the shale composition remained largely unaltered and can be used to draw inferences concerning sediment provenance and palaeoweathering in the source region and/or on intrabasinal erosion surfaces. Evaluation of weathering profiles through sections of the studied supergroups revealed that the shales therein are characterised by high chemical index of alteration (CIA), chemical index of weathering (CIW), and index of compositional variability (ICV), suggesting that the source area was lithologically complex and subject to intense chemical weathering. A progressive change in the chemical composition was identified, from a dominant ultramafic–mafic source for the Fig Tree Group to a progressively felsic–plutonic provenance for the Moodies Group. The West Rand Group of the Witwatersrand Supergroup shows a dominance of tonalite–trondhjemite–granodiorite and calcalkaline granite sources. Compositional profiles through the only major marine shale unit within the Central Rand Group indicate the progressive unroofing of a granitic source in an otherwise greenstone-dominated hinterland during the course of sedimentation. No plausible likely tectonic setting was obtained through geochemical modelling. However, the combination of the systematic shale chemistry, geochronology, and sedimentology in the Witwatersrand Supergroup supports the hypothesised passive margin setting for the >2.98 to 2.91 Ga West Rand Group, and an active continental margin source for the overlying >2.90 to 2.78 Ga Central Rand Group, along with a foreland basin setting for the latter. Ultra-low detection limit analyses of gold and PGE concentrations revealed a variable degree of gold accumulation within pristine unmineralised shales. All the studied shales contain elevated gold and PGE contents relative to the upper continental crust, with marine shales from the Central Rand Group showing the highest Au (±9.85 ppb) enrichment. Based on this variation in the provenance of contemporaneous sediments in different parts of the Kaapvaal Craton, one can infer that the siderophile elements were sourced from a fertile hinterland, but concentrated into the marine shales by a combination of different processes. It is proposed that accumulation of siderophile elements in the studied marine shales was mainly controlled by mechanical coagulation and aggregation. These processes involved suspended sediments, fine gold particles, and other trace elements being trapped in marine environments. Mechanical coagulation and aggregation resulted in gold enrichments by 2–3 orders of magnitude, whereas some of the gold in these marine shales can be reconciled by seawater adsorption into sedimentary pyrite. For the source of gold and PGEs in the studied marine shales in the Kaapvaal Craton, a genetic model is proposed that involves the following: (1) A highly siderophile elements enriched upper mantle domain, herein referred to as “geochemically anomalous mantle domain”, from which the Kaapvaal crust was sourced. This mantle domain enriched in highly siderophile elements was formed either by inhomogeneous mixing with cosmic material that was added during intense meteorite bombardment of the Hadaean to Palaeoarchaean Earth or by plume-like ascent of relics from the core–mantle boundary. In both cases, elevated siderophile elements concentrations would be expected. The geochemically anomalous mantle domain is likely the ultimate source of the Witwatersrand modified palaeoplacer gold deposits and was tapped again ca. 2.054 Ga during the emplacement of the Bushveld Igneous Complex. Therefore, I propose that there is a genetic link (i.e. common geochemically anomalous mantle source) between the Witwatersrand gold deposits and the younger Bushveld Igneous Complex PGE deposits. (2) Scavenging of crustal gold by various surface processes such as trapping of gold from Archaean/Palaeoproterozoic river water on the surface of local photosynthesizing cyanobacterial or microbial mats, and reworking of these mats into erosion channels during flooding events. The above two models complement each other, with model (1) providing a common geological source for the Witwatersrand gold and Bushveld Igneous Complex PGE deposits, and model (2) explaining the processes responsible for Witwatersrand-type gold pre-concentration processes. In sequences such as the Transvaal Supergroup, a less fertile hinterland and/or less reworking of older sediments led to a correspondingly lower gold endowment. These findings indicate temporal distribution of siderophile elements in the upper crust (e.g. marine shales). The overall implications of these findings are that background concentrations of gold and PGEs can be used to target potential exploration areas in other cratons of similar age. This increases the likelihood of finding other Witwatersrand-type gold or Bushveld Igneous Complex-type PGE deposits in other cratons.Der Kaapvaal Kraton beherbergt eine Vielzahl großer Goldlagerstätten (vor allem in der Witwatersrand Hauptgruppe), die von Bergbaugesellschaften in ihrer jeweiligen stratigraphischen Position abgebaut werden. Im diesem Kraton liegen auch die größten Lagerstätten für Platingruppenelemente (vornehmlich im Bushveld Komplex), die aus diversen magmatischen Intrusionskörpern gewonnen werden. Trotz der intensiven und langen Explorationsgeschichte im Bereich des Kaapvaal Kratons ist die Herkunft des Goldes in den Witwatersrand Lagerstätten und die der Platingruppenelemente in den Lagerstätten des Bushveld-Komplex noch ungeklärt und Gegenstand aktueller Diskussionen. Ziel der Arbeit war die geochemische Charakterisierung von Tonschiefern in den Barberton-, Witwatersrand und Transvaal-Hauptgruppen, um Aussagen über deren Provenienz zu treffen und die Gehalte an siderophilen Elementen darin zu ermitteln. Ein verbessertes Verständnis, warum manche archaischen und proterozoischen Einheiten stark mineralisiert sind und andere nicht, sollte bei der Planung zukünftiger Explorationsprojekte dienlich sein. Um dieses Ziel zu erreichen, wurden unalterierte und nicht mineralisierte Proben mariner Tonschiefer aus der Barberton Hauptgruppe (Fig Tree und Moodies Gruppen), der Witwatersrand Hauptgruppe (West Rand und Central Rand Gruppen) und der Transvaal Hauptgruppe (Black Reef Formation und Pretoria Gruppe) aus Untertage Bergbau-Bereichen sowie aus Bohrkernen genommen. Zur Charakterisierung der Tonschiefer kamen verschiedene Methoden zum Einsatz, darunter die Pulverdiffraktometrie (XRD), Durchlichtmikroskopie, Röntgenfluoreszenz (XRF), Optische Emissionsspektroskopie (ICP-OES), Laserablationsmassenspektrometrie (ICP-MS) und Elektronenstrahlmikrosonde (EMPA), sowie Bestimmung der Gold und Platingruppen-Elementkonzentrationen mittels Graphitrohr-AAS nach Voranreicherung mit der Nickelsulfid-Dokimasie. Die untersuchten Tonschiefer verhielten sich seit ihrer Ablagerung als größtenteils geschlossene Systeme. Nur entlang der Kontakte mit unter- und überlagernden grobkörnigeren Metasedimentgesteinen sowie entlang durchkreuzender Störungen, Quarzadern und Gängen konnte lokal nennenswerte Alteration festgestellt werden. Solche Zonen wurden explizit von der Provenienz-Analyse ausgenommen. Systematische Unterschiede in der primären chemischen Zusammensetzung einzelner Tonschiefer-Abfolgen belegen unterschiedliche Sedimentquellen. So wurde in der Barberton Hauptgruppe der Sedimenteintrag der Fig Tree-Gruppe von einer ultramafisch-mafischen Quelle dominiert, während in der Moodies-Gruppe felsische Quellen eine zunehmende Rolle spielten. In der Witwatersrand Hauptgruppe wurde eine Dominanz von Tonalit-Trondhjemit-Granodiorit sowie kalkalkaline Granite im Liefergebiet der West Rand Gruppe festgestellt, während in der Central Rand Gruppe anfänglich mafisch-ultramafische Gesteine im Sedimentliefergebiet vorherrschten, im Lauf der Zeit aber granitische Gesteine mehr und mehr durch Erosion im Hinterland freigelegt worden waren. Die Geochemie der Witwatersrand Tonschiefer unterstützt die Hypothese, dass die Sedimente der West Rand Gruppe an einem passiven Kontinentalrand abgelagert wurden, jene der Central Rand Gruppe in einem Vorlandbecken. Alle untersuchten archaischen Tonschiefer zeigen, verglichen mit dem Durchschnitt der oberen Erdkruste, deutlich erhöhte Gehalte an Gold und Platingruppenelementen, wobei die marinen Tonschiefer aus der Central Rand Gruppe mit durchschnittlich 9,85 ppm Au die höchsten Konzentrationen aufweisen. Die Gehalte an siderophilen Elementen in der palaeoproterozoischen Transvaal Hauptgruppe nähern sich hingegen typischen kontinentalen Krustenwerten an. Der verstärkte Eintrag von Au und PGE in die archaischen marinen tonigen Sedimente wird durch mechanische Koagulation und Aggregation erklärte, wobei feinstkörnige Goldpartikel im suspendierten Sediment weit ins Meer transportiert worden sind. Adsorption von Au aus Meerwasser an syn-sedimentärem Pyrit spielte auch eine Rolle, aber keine ausschlaggebende. Für die Quelle des Goldes und der Platingruppenelemente in den untersuchten Tonschiefern wurde folgendes genetisches Modell entwickelt. (1) Es wird angenommen, dass sich die Kaapvaal-Kruste aus einem Mantelreservoir differenzierte, welches an siderophilen Elementen angereichert war. Diese Anreicherung könnte entweder das Produkt eines nicht vollständig homogenisierten Eintrags kosmischen Materials sein, welches im Hadaikum oder im Paläoarchaikum durch intensives Meteoritenbombardement eingebracht wurde, oder durch den Aufstieg eines Manteldiapirs aus dem Bereich der Kern-Mantel-Grenze. (2) Tiefgründige Verwitterung unter anoxischen Bedingungen ermögliche die Freisetzung großer Mengen von Au, welches in gelöster Form über Oberflächenwässer in den archaischen Ozean transportiert wurde. Hinweise auf solch intensive Verwitterung liefern die geochemischen Daten der hier untersuchten Tonschiefern, insbesondere hohe chemische Alterationsindizes. Fixierung dieses Goldes durch verschiedene Oberflächenprozesse, wie Filterung aus archaischen/paläoproterozoischen Flüssen durch Photosynthese-betreibende Bakterienrasen führte vor allem im Mesoarchaikum in Zeiten der Sedimentation der Central Rand Gruppe zu lokal extremen Goldanreicherungen, die in der Folge durch Erosion und mechanischen Transport großteils weiter umgelagert wurden. Punkt 1 könnte eventuell die räumliche Nähe der weltweit größten bekannten Goldanomalie im Witwatersrand Becken und der größten PGE-Anomalie im Bushveld Komplex erklären. In wie weit die erhöhten Hintergrundkonzentrationen von Gold und Platingruppenelementen im Kaapvaal Kraton einzigartig sind, gilt es in zukünftigen Studien dieser Art auch an marinen Tonschiefern aus dem Archaikum in anderen Kratonen zu testen

Dry laboratories – Mapping the required instrumentation and infrastructure for online monitoring, analysis, and characterization in the mineral industry

Dry laboratories (dry labs) are laboratories dedicated to using and creating data (they are data-centric). Several aspects of the minerals industry (e.g., exploration, extraction and beneficiation) generate multi-scale and multivariate data that are ultimately used to make decisions. Dry labs and digitalization are closely and intricately linked in the minerals industry. This paper focuses on the instrumentation and infrastructure that are required for accelerating digital transformation initiatives in the minerals sector. Specifically, we are interested in the ability of current and emerging instrumentation, sensors and infrastructure to capture relevant information, generate and transport high-quality data. We provide an essential examination of existing literature and an understanding of the 21st century minerals industry. Critical analysis of the literature and review of the current configuration of the minerals industry revealed similar data management and infrastructure needs for all segments of the minerals industry. There are, however, differences in the tools and equipment used at different stages of the mineral value chain. As demand for data-driven approaches grows, and as data resulting from each segment of the minerals industry continues to increase in abundance, diversity and dimensionality, the tools that manage and utilize such data should evolve in a way that is more transdisciplinary (e.g., data management, artificial intelligence, machine learning and data science). Ideally, data should be managed in a dry lab environment, but minerals industry data is currently and historically disaggregated. Consequently, digitalization in the minerals industry must be coupled with dry laboratories through a systematic transition. Sustained generation of high-quality data is critical to sustain the highly desirable uses of data, such as artificial intelligence-based insight generation.Validerad;2023;Nivå 2;2023-01-09 (hanlid);Funder: Swedish government; Centre for Advanced Mining and Metallurgy (CAMM)</p

Investigation of the effect of hydrocarbon spillages and their interaction with alteration minerals on the flotation of UG2 PGE ore

Raw data from the MSc thesis 'Investigation of the effect of hydrocarbon spillages and their interaction with alteration minerals on the flotation of UG2 PGE ore' by Thendo A. Tshinavhe, 2023. Centre for Minerals Research, Department of Chemical Engineering, University of Cape Town. </p

The valorisation of platinum group metals from flotation tailings: A review of challenges and opportunities

Flotation tailings from South Africa’s platinum group minerals (PGM) represent complex polymetallic orebodies comprising a low-grade platinum group elements (PGE) content and complex mineralogical composition. Nevertheless, given the valuable mineral potential in the tailings, it is understandable that the substantial historic tailings deposits and sizeable annual production volume from primary processes represent a potential secondary resource. For several decades, valorising the PGM tailing materials received very little interest due to limitations associated with extractive metallurgical technology to achieve economically viable PGE extraction. The early 21st century saw the coming online of technologies, including but not limited to ultrafine grinding, suitable to meet challenges in primary metallurgical treatment processes to recover valuable minerals from ultrafine particle fractions, which could not otherwise be recovered. More so, such processes were critical in improving the liberation of partially liberated particles without compromising additional ultrafine generation. These technologies led to the development of re-treatment pilot tests and subsequent industrial re-treatment recovery processes. The current industrial re-treatment approach – via tertiary scavenging flotation circuits – renders profit in small increments up to 1 ∼ 2% additional recovery relative to the primary plant head grade. These small increments relate to about ∼12–30% PGE recovery of the feed grade to the re-treatment circuit, thereby enhancing the primary plant's overall economics as well as aiding the supply of critical metals to meet global demands. With a focus on South Africa, this review provides an overview of (a) the current and future drivers of the precious metals global demand; (b) proffers discussion on the PGM characteristic mineralogy and the metallurgical value chain; (c) relates the parent orebodies (“reefs”) mineral characteristics to the inherent processed tailings; (d) estimates the economic potential these massive processed waste materials contain, (e) provides an overview of existing technologies that are industrially used in tailing re-treatment plants; and (f) outlines a comprehensive understanding of the nature of value minerals rejection to tailings

Assessing cobalt supply sustainability through production forecasting and implications for green energy policies

Transitioning to a decarbonized and circular economy is paramount for climate change mitigation and sustainable development. In this paper we assess the global production trends of cobalt, an energy-transition metal (ETM), and its supply sustainability. Accurate production forecasting of ETMs is essential to understand the dynamics of energy supply security and adequately plan for a change from fossil fuel energy to renewable energy production. Evaluations of market concentrations demonstrate that cobalt is a high-risk market characterized by production fluctuations and supply-chain complexities. We forecast the cobalt production using several methods. Results from both of the Auto Regressive Integrated Moving Average (ARIMA) and Holt's methods show a linear increase in world cobalt production for the short term, while a Hubbert model predicts a world production decline beginning in the late 2010s. These predictions, coupled with geopolitical, socio-environmental, and techno-economic influences on the market, reinforce the concern regarding cobalt supply sustainability. Although alternative avenues for sourcing cobalt, such as secondary urban mining and stockpiling exist, they are unlikely to become major suppliers in the short term, which highlights the need to accurately forecast primary production. Increasing interests in critical raw materials (CRMs) in policy spheres also heightens the necessity to anticipate the future of cobalt supply as governmental entities acknowledge the imbalance of CRMs in international trade. Well-researched and well-designed policies, that incorporate environmental sustainability and non-discriminatory economic growth, can facilitate an equitable shift to a greener and more circular economy. At the forefront of this shift should be ethical environmental and resource governance that recognizes the inequalities in socio-economic development and energy-transition, and mandates for a just transition towards a low carbon future.Validerad;2021;Nivå 2;2021-10-21 (beamah);Forskningsfinanziär: National Research Foundation (NRF) Thuthuka (121973)</p