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Geochemistry and Mineralogy of Ni-Co Laterite Deposits

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

Deadline for manuscript submissions: closed (16 December 2022) | Viewed by 30434

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Special Issue Editors

Dr. Cristina Domènech

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Guest Editor

Department of Mineralogy, Petrology and Applied Geology, Universitat de Barcelona, 08028 Barcelona, Spain
Interests: reactive transport modelling of water-rock interaction and mineral deposits formation; thermodynamic data base development; thermodynamics and kinetics of natural waters; groundwater and soil pollution; geochemical behaviour of heavy and trace elements

Dr. Cristina Villanova-de-Benavent

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Guest Editor

Department of Mineralogy, Petrology and Applied Geology, Universitat de Barcelona, 08028 Barcelona, Spain
Interests: geochemistry; mineralogy; mineral chemistry and ore forming processes in Ni-Co(-PGE) laterite deposits; REE bauxites; ion adsorption REE deposits; Fe-Ti(-V) oxide anorthosite complexes

Special Issue Information

Dear Colleagues,

Ni-Co laterites, which are regoliths formed after the chemical weathering of ultramafic rocks in tropical-subtropical regimes, have been the subject of study for many decades. This has provided a good picture of their structure, element distribution and mineralogy, especially of Ni-bearing minerals (e.g., garnierites, Ni-serpentines, Ni-smectites, asbolane-lithiophorite, Fe-oxyhydroxides). Interestingly, in the last decade, Ni-laterites experienced a comeback in the literature, for many reasons.

Recently, Ni-Co laterites have surpassed Ni-sulphides as the main source of Ni, accounting for about 50% of the current world's Ni production and hosting close to 60% of the world’s land-based resources. In addition, the improvement of the existing analytical techniques, and the appearance of new ones, have shed light on some of the unknowns, and given new perspectives. In particular, it has been revealed that, besides Ni, these laterite deposits usually contain other elements that are becoming more and more demanded (so-called critical metals or high-tech elements). Ni-laterite deposits are worthy targets of Co, Sc and/or platinum group elements (PGE).

However, there are still a lot of unknowns regarding the mobility of elements, the mineralogy and/or the environmental impact of Ni-Co laterite deposits, and it is of crucial importance to solve some of the uncertainties which have arisen from previous investigations.

The main objective of this Special Issue of Minerals is to publish the latest research on trace element geochemistry, and minerals containing Ni and/or critical metals (e.g. Co, Sc, PGE, REE…) found in Ni-laterite deposits, including their tailings, in order to provide new information about their texture, chemical composition, crystal chemistry, and genesis, which is paramount to improving the efficiency for the recovery of target elements.

We both kindly encourage you to join us. Let's make this issue a highly referenced one!

Dr. Cristina Domènech
Dr. Cristina Villanova-de-Benavent
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Ni-Co laterite
Garnierite
Ni-bearing goethite
Sc-bearing goethite
Asbolane
Lithiophorite–asbolane “intermediates”
Platinum group minerals

Published Papers (11 papers)

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Research

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23 pages, 21239 KiB

Open AccessFeature PaperArticle

Geochemistry and Mineralogy of the Clay-Type Ni-Laterite Deposit of San Felipe (Camagüey, Cuba)

by Esperança Tauler, Salvador Galí, Cristina Villanova-de-Benavent, Alfonso Chang-Rodríguez, Kenya Núñez-Cambra, Giorgi Khazaradze and Joaquín Antonio Proenza

Minerals 2023, 13(10), 1281; https://0-doi-org.brum.beds.ac.uk/10.3390/min13101281 - 29 Sep 2023

Viewed by 840

Abstract

The Ni-laterite deposit at the San Felipe plateau, located 30 km northwest of Camagüey, in central Cuba, is the best example of a clay-type deposit in the Caribbean region. San Felipe resulted from the weathering of mantle peridotites of the Cretaceous Camagüey ophiolites. In this study, a geochemical and mineralogical characterization of two profiles (83 and 84) from the San Felipe deposit has been performed by XRF, ICP-MS, quantitative XRPD, oriented aggregate mount XRD, SEM, FE-SEM, and EMPA. Core 83, with a length of 23 m and drilled in the central part of the plateau, presents a notable concentration of cryptocrystalline quartz fragments and a rather poor content of NiO, averaging 0.87 wt.%. Core 84, which is 12 m long and drilled at the border of the plateau, lacks silica fragments and presents a higher NiO content, averaging 1.79 wt.%. The smectite structural formulae reveal that they evolve from trioctahedral to dioctahedral towards the top of the laterite profiles. Quantitative XRD analyses indicate that smectite is a dominant Ni-bearing phase, accompanied by serpentine and minor chlorite. Serpentine, as smectite, is enriched in the less soluble elements Fe³⁺, Al, and Ni towards the top of the profiles. Core 83 seems to have been affected by collapses and replenishments, whereas core 84 may have remained undisturbed. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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22 pages, 22530 KiB

Open AccessArticle

Metal Mobility in Embryonic-to-Proto-Ni-Laterite Profiles from Non-Tropical Climates

by José María González-Jiménez, Cristina Villanova-de-Benavent, Lola Yesares, Claudio Marchesi, David Cartwright, Joaquín A. Proenza, Luis Monasterio-Guillot and Fernando Gervilla

Minerals 2023, 13(7), 844; https://0-doi-org.brum.beds.ac.uk/10.3390/min13070844 - 22 Jun 2023

Viewed by 1203

Abstract

We evaluated the mobility of a wide suite of economic metals (Ni, Co, REE, Sc, PGE) in Ni-laterites with different maturities, developed in the unconventional humid/hyper-humid Mediterranean climate. An embryonic Ni-laterite was identified at Los Reales in southern Spain, where a saprolite profile of ~1.5 m thick was formed at the expense of peridotites of the subcontinental lithospheric mantle. In contrast, a more mature laterite was reported from Camán in south-central Chile, where the thicker (~7 m) weathering profile contains well-developed lower and upper oxide horizons. This comparative study reveals that both embryonic and mature laterites can form outside the typical (sub)-tropical climate conditions expected for lateritic soils, while demonstrating a similar chemical evolution in terms of major (MgO, Fe₂O₃, and Al₂O₃), minor (Ni, Mn, Co, Ti, Cr), and trace (REE, Y, Sc, PGE, Au) element concentrations. We show that, even in the earliest stages of laterization, the metal remobilization from primary minerals can already result in uneconomic concentration values. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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26 pages, 12238 KiB

Open AccessFeature PaperArticle

Pseudo-Karst Silicification Related to Late Ni Reworking in New Caledonia

by Michel Cathelineau, Marie-Christine Boiron, Jean-Louis Grimaud, Sylvain Favier, Yoram Teitler and Fabrice Golfier

Minerals 2023, 13(4), 518; https://0-doi-org.brum.beds.ac.uk/10.3390/min13040518 - 06 Apr 2023

Cited by 2 | Viewed by 1071

Abstract

Silicification in New Caledonian pseudo-karsts developed on peridotite was assessed using δ¹⁸O and δ³⁰Si pairs on quartz cements. The objective was to document the chronology of pseudo-karst development and cementation relative to geomorphic evolution. The latter began at the end of the Eocene with the supergene alteration of peridotites and the subsequent formation of extended lateritic weathering profiles. Neogene uplift favoured the dismantling of these early lateritic profiles and valley deepening. The river incision resulted in (i) the stepping of a series of lateritic paleo-landforms and (ii) the development of a pseudo-karst system with subvertical dissolution pipes preferentially along pre-existing serpentine faults. The local collapse of the pipes formed breccias, which were then cemented by white quartz and Ni-rich talc-like (pimelite). The δ³⁰Si of quartz, ranging between −5‰ and −7‰, are typical of silcretes and close to the minimum values recorded worldwide. The estimated δ¹⁸O of −6 to −12‰ for the fluids are lower than those of tropical rainfall typical of present-day and Eocene–Oligocene climates. Evaporation during drier climatic episodes is the main driving force for quartz and pimelite precipitation. The silicification presents similarities with silcretes from Australia, which are considered predominantly middle Miocene in age. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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42 pages, 12784 KiB

Open AccessArticle

Evolution of the Piauí Laterite, Brazil: Mineralogical, Geochemical and Geomicrobiological Mechanisms for Cobalt and Nickel Enrichment

by Agnieszka Dybowska, Paul F. Schofield, Laura Newsome, Richard J. Herrington, Julian F. W. Mosselmans, Burkhard Kaulich, Majid Kazemian, Tohru Araki, Thomas J. Skiggs, Jens Kruger, Anne Oxley, Rachel L. Norman and Jonathan R. Lloyd

Minerals 2022, 12(10), 1298; https://0-doi-org.brum.beds.ac.uk/10.3390/min12101298 - 14 Oct 2022

Cited by 3 | Viewed by 2752

Abstract

The Piauí laterite (NE Brazil) was initially evaluated for Ni but also contains economic concentrations of Co. Our investigations aimed to characterise the Co enrichment within the deposit; by understanding the mineralogy we can better design mineral processing to target Co recovery. The laterite is heterogeneous on the mineralogical and lithological scale differing from the classic schematic profiles of nickel laterites, and while there is a clear transition from saprolite to more ferruginous units, the deposit also contains lateral and vertical variations that are associated with both the original intrusive complex and also the nature of fluid flow, redox cycling and fluctuating groundwater tables. The deposit is well described by the following six mineralogical and geochemical units: SAPFE, a clay bearing ferruginous saprolite; SAPSILFE, a silica dominated ferruginous saprolite; SAPMG, a green magnesium rich chlorite dominated saprolite; SAPAL, a white-green high aluminium, low magnesium saprolite; saprock, a serpentine and chlorite dominated saprolite and the serpentinite protolith. Not all of these units are ‘ore bearing’. Ni is concentrated in a range of nickeliferous phyllosilicates (0.1–25 wt%) including serpentines, talc and pimelite, goethite (up to 9 wt%), magnetite (2.8–14 wt%) and Mn oxy-hydroxides (0.35–19 wt%). Lower levels of Ni are present in ilmenites, chromites, chlorite and distinct small horizons of nickeliferous silica (up to 3 wt% Ni). With respect to Co, the only significant chemical correlation is with Mn, and Mn oxy-hydroxides contain up to 14 wt% Co. Cobalt is only present in goethite when Mn is also present, and these goethite grains contain an average of 0.19 wt% Co (up to a maximum of 0.65 wt%). The other main Co bearing minerals are magnetite (0.41–1.89 wt%), chlorite (up to 0.45 wt%) and ilmenite (up to 0.35 wt%). Chemically there are three types of Mn oxy-hydroxide, asbolane, asbolane-lithiophorite intermediates and romanechite. Spatially resolved X-ray absorption spectroscopy analysis suggests that the Co is present primarily as octahedrally bound Co³⁺ substituted directly into the MnO₆ layers of the asbolane-lithiophorite intermediates. However significant levels of Co²⁺ are evident within the asbolane-lithiophorite intermediates, structurally bound along with Ni in the interlayer between successive MnO₆ layers. The laterite microbial community contains prokaryotes and few fungi, with the highest abundance and diversity closest to ground level. Microorganisms capable of metal redox cycling were identified to be present, but microcosm experiments of different horizons within the deposit demonstrated that stimulated biogeochemical cycling did not contribute to Co mobilisation. Correlations between Co and Mn are likely to be a relic of parent rock weathering rather than due to biogeochemical processes; a conclusion that agrees well with the mineralogical associations. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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26 pages, 11695 KiB

Open AccessArticle

Co–Mn Mineralisations in the Ni Laterite Deposits of Loma Caribe (Dominican Republic) and Loma de Hierro (Venezuela)

by Cristina Domènech, Cristina Villanova-de-Benavent, Joaquín A. Proenza, Esperança Tauler, Laura Lara, Salvador Galí, Josep M. Soler, Marc Campeny and Jordi Ibañez-Insa

Minerals 2022, 12(8), 927; https://0-doi-org.brum.beds.ac.uk/10.3390/min12080927 - 22 Jul 2022

Cited by 3 | Viewed by 2582

Abstract

Cobalt demand is increasing due to its key role in the transition to clean energies. Although the main Co ores are the sediment-hosted stratiform copper deposits of the Democratic Republic of the Congo, Co is also a by-product of Ni–Co laterite deposits, where Co extraction efficiency depends, among other factors, on the correct identification of Co-bearing minerals. In this paper, we reported a detailed study of the Co mineralisation in the Ni–Co laterite profiles of Loma Caribe (Dominican Republic) and Loma de Hierro (Venezuela). Cobalt is mainly associated with Mn-oxyhydroxide minerals, with a composition between Ni asbolane and lithiophorite, although a Co association with phyllosilicates has also been recorded in a Loma de Hierro deposit. In Loma Caribe, Co-bearing Mn-oxyhydroxide minerals mainly developed colloform aggregates, and globular to spherulitic grains, while in Loma de Hierro, they displayed banded colloform, fibrous or tabular textures. Most of the compositional analyses of Mn-oxyhydroxides yielded 20 and 40 wt.% Mn, with Ni and Co up to 16 and 10 wt.%, respectively. In both profiles, Mn-bearing minerals were mainly found in the transition from the oxide horizon to the saprolite, as observed in other laterite profiles in the world, where the precipitation of Mn-bearing minerals is enhanced because of the pore solution saturation and pH increase. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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22 pages, 6792 KiB

Open AccessArticle

Evaluation of Sc Concentrations in Ni-Co Laterites Using Al as a Geochemical Proxy

by Yoram Teitler, Sylvain Favier, Jean-Paul Ambrosi, Brice Sevin, Fabrice Golfier and Michel Cathelineau

Minerals 2022, 12(5), 615; https://0-doi-org.brum.beds.ac.uk/10.3390/min12050615 - 12 May 2022

Cited by 5 | Viewed by 2152

Abstract

Scandium (Sc) is used in several modern industrial applications. Recently, significant Sc concentrations (~100 ppm) were reported in some nickel-cobalt lateritic ores, where Sc may be valuably co-produced. However, Sc is typically not included in routine analyses of Ni-Co ores. This contribution examines the relevance of using routinely analysed elements as geochemical proxies for estimating Sc concentration and distribution. Three Ni-Co lateritic deposits from New Caledonia were investigated. In each deposit, Sc is well correlated with Al₂O₃. The slopes of deposit-scale Sc-Al₂O₃ regression lines are remarkably controlled by the composition of enstatite from the parent peridotite. In all deposits, maximum Sc enrichment occurs in the yellow limonite, above the highest Ni and Co enrichment zones. Sc- and Al-bearing crystalline goethite is predominant in the oxide-rich zones, though Sc shows a higher affinity for amorphous iron oxides than Al. We propose that, in already assayed Ni-Co lateritic ores, the concentration and distribution of Sc can be estimated from that of Al. Deposit-scale Sc-Al₂O₃ correlations may be determined after analysing a limited number of spatially and chemically representative samples. Therefore, mining operators may get a first-order evaluation of the Sc potential resource in Ni-Co lateritic deposits at low additional costs. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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24 pages, 17284 KiB

Open AccessArticle

On the Influence and Correction of Water Content on pXRF Analysis of Lateritic Nickel Ore Deposits in the Context of Open Pit Mines of New-Caledonia

by Valérie Laperche, Cyrille Metayer, Julien Gaschaud, Philippe Wavrer and Thomas Quiniou

Minerals 2022, 12(4), 415; https://0-doi-org.brum.beds.ac.uk/10.3390/min12040415 - 29 Mar 2022

Cited by 4 | Viewed by 1664

Abstract

In a number of applications, the use of portable X-ray fluorescence (pXRF) instruments offers a time and cost-saving alternative to standard laboratory instruments. This is particularly true in a mining context where decisions must be taken quickly in the field. However, pXRF is a technique known to be efficient, provided that samples are well prepared, i.e., dried and finely ground. On the mine face, little-to-no sample preparation is conceivable as mining vehicles must be able to operate continuously. Therefore, solutions have to be found even for raw materials and one of the most critical problems is the sample water content, in particular in the context of open pit mines in a tropical area. A large number of analysis shows that knowledge of humidity enables the measured concentration to be effectively corrected for the three instruments used (Niton, X-met, Titan). It is possible to overcome the difficulty of measuring water content in the field by fixing it to its maximum value (saturation). The results show that the saturation method is reliable, or at least, promising. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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22 pages, 6130 KiB

Open AccessArticle

Mineralogical and Geochemical Characterization of the Sta. Cruz Nickel Laterite Deposit, Zambales, Philippines

by Karmina A. Aquino, Carlo A. Arcilla, Christian Schardt and Carmela Alen J. Tupaz

Minerals 2022, 12(3), 305; https://0-doi-org.brum.beds.ac.uk/10.3390/min12030305 - 27 Feb 2022

Cited by 10 | Viewed by 6529

Abstract

In this study, we present mineralogical and geochemical characterization of samples systematically collected from a nickel laterite profile at the Sta. Cruz nickel laterite deposit, Zambales, Philippines. Wavelength-dispersive X-ray fluorescence spectroscopy (WDSXRF), mass-balance element mobility calculations, transmitted and reflected light microscopy, and previously reported results from coupled X-ray diffraction (XRD) and Rietveld refinement analyses reveal that the laterite profile investigated is composed of two main horizons—the limonite and saprolite zones—separated by a thin transitional zone. Based primarily on the mineral assemblage and major element chemistry, the main zones are further subdivided into subzones: upper limonite, lower limonite, transitional zone, upper saprolite, and lower saprolite. Garnierite veins were observed cutting the upper and lower saprolite subzones. Investigation of the structure of goethite within the limonite zone via Rietveld refinement shows that the crystallinity of goethite decreases with increasing Ni content and increasing crystallite size. This suggests that upwards through the limonite zone, as goethite ages, its crystallinity increases, which possibly results in the removal of Ni from its crystal structure and eventual remobilization to the lower laterite zones. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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17 pages, 4607 KiB

Open AccessFeature PaperArticle

Occurrence of SiC and Diamond Polytypes, Chromite and Uranophane in Breccia from Nickel Laterites (New Caledonia): Combined Analyses

by Yassine El Mendili, Beate Orberger, Daniel Chateigner, Jean-François Bardeau, Stéphanie Gascoin, Sébastien Petit and Olivier Perez

Minerals 2022, 12(2), 196; https://0-doi-org.brum.beds.ac.uk/10.3390/min12020196 - 02 Feb 2022

Cited by 2 | Viewed by 2510

Abstract

Different techniques have been combined to identify the structure and the chemical composition of siliceous breccia from a drill core of nickel laterites in New Caledonia (Tiebaghi mine). XRD analyses show quartz as a major phase. Micro-Raman spectroscopy confirmed the presence of reddish microcrystalline quartz as a major phase with inclusion of microparticles of iron oxides and oxyhydroxide. Lithoclasts present in breccia are composed of lizardite, chrysotile, forsterite, hedenbergite and saponite. The veins cutting through the breccia are filled with Ni-bearing talc. Furthermore, for the first time, we discovered the presence of diamond microcrystals accompanied by moissanite polytypes (SiC), chromite (FeCr₂O₄) and uranophane crystals (Ca(UO₂)₂(SiO₃OH)₂.5(H₂O)) and lonsdaleite (2H-[C-C]) in the porosities of the breccia. The origin of SiC and diamond polytypes are attributed to ultrahigh-pressure crystallization in the lower mantle. The SiC and diamond polytypes are inherited from serpentinized peridotites having experienced interaction with a boninitic melt. Serpentinization, then weathering of the peridotites into saprolite, did not affect the resistant SiC polytypes, diamond and lonsdaleite. During karstification and brecciation, silica rich aqueous solutions partly digested the saprolite. Again, the SiC polymorph represent stable relicts from this dissolution process being deposited in breccia pores. Uranophane is a neoformed phase having crystallized from the silica rich aqueous solutions. Our study highlights the need of combining chemical and mineralogical analytical technologies to acquire the most comprehensive information on samples, as well as the value of Raman spectroscopy in characterizing structural properties of porous materials. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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18 pages, 7164 KiB

Open AccessArticle

Objective Domain Boundaries Detection in New Caledonian Nickel Laterite from Spectra Using Quadrant Scan

by Ayham Zaitouny, Erick Ramanaidou, June Hill, David M. Walker and Michael Small

Minerals 2022, 12(1), 49; https://0-doi-org.brum.beds.ac.uk/10.3390/min12010049 - 29 Dec 2021

Cited by 3 | Viewed by 2294

Abstract

Modelling of 3D domain boundaries using information from drill holes is a standard procedure in mineral exploration and mining. Manual logging of drill holes can be difficult to exploit as the results may not be comparable between holes due to the subjective nature of geological logging. Exploration and mining companies commonly collect geochemical or mineralogical data from diamond drill core or drill chips; however, manual interpretation of multivariate data can be slow and challenging; therefore, automation of any of the steps in the interpretation process would be valuable. Hyperspectral analysis of drill chips provides a relatively inexpensive method of collecting very detailed information rapidly and consistently. However, the challenge of such data is the high dimensionality of the data’s variables in comparison to the number of samples. Hyperspectral data is usually processed to produce mineral abundances generally involving a range of assumptions. This paper presents the results of testing a new fast and objective methodology to identify the lithological boundaries from high dimensional hyperspectral data. This method applies a quadrant scan analysis to recurrence plots. The results, applied to nickel laterite deposits from New Caledonia, demonstrate that this method can identify transitions in the downhole data. These are interpreted as reflecting mineralogical changes that can be used as an aid in geological logging to improve boundary detection. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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Review

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31 pages, 4737 KiB

Open AccessFeature PaperReview

Origin of Critical Metals in Fe–Ni Laterites from the Balkan Peninsula: Opportunities and Environmental Risk

by Maria Economou-Eliopoulos, Magdalena Laskou, Demetrios G. Eliopoulos, Ifigeneia Megremi, Sofia Kalatha and George D. Eliopoulos

Minerals 2021, 11(9), 1009; https://0-doi-org.brum.beds.ac.uk/10.3390/min11091009 - 16 Sep 2021

Cited by 6 | Viewed by 3377

Abstract

As the global energy sector is expected to experience a gradual shift towards renewable energy sources, access to special metals in known resources is of growing concern within the EU and at a worldwide scale. This is a review on the Fe–Ni ± Co-laterite deposits in the Balkan Peninsula, which are characterized by multistage weathering/redeposition and intense tectonic activities. The ICP-MS analyses of those laterites indicated that they are major natural sources of Ni and Co, with ore grading from 0.21 to 3.5 wt% Ni and 0.03 to 0.31 wt% Co, as well as a significant Sc content (average 55 mg/kg). The SEM-EDS analyses revealed that fine Fe-, Ni-, Co-, and Mn-(hydr)oxides are dominant host minerals and that the enrichment in these elements is probably controlled by the post-formation evolution of initial ore redeposition. The paucity of rare earth element (REE) within the typical Fe–Ni laterite ore and the preferential occurrence of Co (up to 0.31 wt%), REE content (up to 6000 mg/kg ΣREE), and REE-minerals along with Ni, Co, and Mn (asbolane and silicates) towards the lowermost part of the Lokris (C. Greece) laterite ore suggest that their deposition is controlled by epigenetic processes. The platinum-group element (PGE) content in those Fe–Ni laterites, reaching up to 88 μg/kg Pt and 26 μg/kg Pd (up to 186 μg/kg Pd in one sample), which is higher than those in the majority of chromite deposits associated with ophiolites, may indicate important weathering and PGE supergene accumulation. Therefore, the mineralogical and geochemical features of Fe–Ni laterites from the Balkan Peninsula provide evidence for potential sources of certain critical metals and insights to suitable processing and metallurgical methods. In addition, the contamination of soil by heavy metals and irrigation groundwater by toxic Cr(VI), coupled with relatively high Cr(VI) concentrations in water leachates for laterite samples, altered ultramafic rocks and soils neighboring the mining areas and point to a potential human health risk and call for integrated water–soil–plant investigations in the basins surrounding laterite mines. Full article

(This article belongs to the Special Issue Geochemistry and Mineralogy of Ni-Co Laterite Deposits)

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