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

Maria Economou-Eliopoulos,Demetrios Eliopoulos,George Eliopoulos,Magdalena Laskou,Sofia Kalatha,Ifigeneia Megremi

doi:10.3390/min11091009

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.

Highlights

As gradual shift towards renewable energy sources on a global scale, access to particular raw materials or critical metals (CM), such as platinum-group elements (PGE), rare earth elements (REE), and scandium (Sc), with potential presence in known resources is a growing concern within the European Union (EU) and in a worldwide scale [1,2]. The production for these metals is mostly derived from magmatic deposits, volcanogenic massive sulfide (VMS) deposits, the black shale-hosted deposit in Finland and Sweden, and deposits of supergene origin associated with the release of major and trace elements from the alteration of related rocks [1,3,4,5,6,7], deposits of Fe–Ni ± Co laterite may be a potential resource for critical metals as well [8,9]
The present study focuses on the combination of Ni–Co–Mn mineral chemistry with geochemical characteristics of laterites from the Balkan Peninsula, which offer a variety of laterite types
The presented data combined with the review of the available geological, mineralogical, and geochemical features of Fe–Ni ± Co laterites from the Balkan Peninsula led us to the following conclusions:

Summary

Introduction

As gradual shift towards renewable energy sources on a global scale, access to particular raw materials or critical metals (CM), such as platinum-group elements (PGE), rare earth elements (REE), and scandium (Sc), with potential presence in known resources is a growing concern within the European Union (EU) and in a worldwide scale [1,2]. The type of Ni– Co laterites developed by chemical weathering of ultramafic rocks with potential post redeposition enrichment of weathering products may occur above weathered bedrock. Among others, they have been described in the Philippines (Taganito/Adlay), in Western Australia (The Murrin Murrin deposit), in New Caledonia, Indonesia, and the Dominican Republic [11,12,13]. The Fe–Ni laterite deposits in the Balkan Peninsula are associated with ophiolites, which represent a remnant of the Tethyan oceanic lithosphere, located in the Mirdita–Sub-Pelagonian and Pelagonian geotectonic zones [14]. Kastoria, Vermion, Paleochori, Edessa, Olympos) (Figure 1) [15,16,17,18,19,20,21]

Methods

Findings

Discussion

Conclusion