Metallic Resources 1 E-Book
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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Metallic resources play a huge role in many fields: in the energy transition, the development of new technologies and the production and storage of green energy. Metallic Resources 1 presents various studies in notable European metallogenic regions or deposits that enable us to tackle the question of the concentration of metals, especially strategic metals, in various geodynamic settings. An understanding of the geological processes that lead to the formation of deposits and influence their concentrations in the Earth's crust is of the utmost importance when it comes to uncovering new mineral resources. This book puts forward various different methodological approaches necessary in the study of deposits of metallic resources, from field observations to microanalysis. A study of specific geo-politico-economic frameworks is also presented.
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Veröffentlichungsjahr: 2023
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Table of Contents
Cover
Table of Contents
Title Page
Copyright Page
1 The Rare Earth Resources of Europe and Greenland: Mining Potential and Challenges
1.1. Introduction
1.2. The extreme diversity of rare earths
1.3. The economy of rare earths in the world and their place in Europe
1.4. Classification of rare earth deposits
1.5. Rare earths deposits in Europe
1.6. The rare earths deposits of Greenland
1.7. The origin of the rare earth deposits in Europe and Greenland
1.8. Strengths and weaknesses of rare earths deposits in Europe and Greenland
1.9. Conclusion
1.10. Acknowledgments
1.11. References
2 The Cornubian Batholith: Post-Collisional Variscan Granites and Resources
2.1. Introduction
2.2. Tectonic context of magmatism and resources
2.3. Lamprophyres and basalts
2.4. The Cornubian Batholith and associated felsic igneous rocks
2.5. Granite-related mineralization
2.6. Post-granite mineralization
2.7. China clay
2.8. The past, present and future of the resources sector in SW England
2.9. Environmental, cultural and social impact of mining
2.10. References
3 The W Deposit at Panasqueira (Portugal): A Critical Bibliographical Review
3.1. Introduction
3.2. Geological context
3.3. Relative chronology of the alteration and mineralization stages
3.4. The opening of the veins
3.5. P and T conditions at the early and late stages
3.6. Characterization of the origin of fluids
3.7. Role of the Panasqueira granites
3.8. Panasqueira: a magmatic and hydrothermal system of crustal scale
3.9. References
Appendix 1: The Rare Earth Resources of Europe and Greenland: Mining Potential and Challenges
A1.1. Table summarizing rare earth deposits listed in the paper written for this book
Appendix 2: The Cornubian Batholith: Post-Collisional Variscan Granites and Resources
A2.1. Ore and mineral deposits/occurrences associated with the Cornubian Batholith and mentioned in the chapter
Appendix 3: The Panasqueira W Deposit (Portugal): A Critical Bibliographic Review
A3.1. Estimate of the tungsten endowment in Variscan Western Europe
A3.2. Additional figures
A3.3. Inventory of samples used for the plates
A3.4. Mass balances and source of fluids
A3.5. References
List of Authors
Index
Summary of Volume 2
End User License Agreement
List of Tables
Chapter 1
Table 1.1. Minerals valued by the extraction industry (Tuduri et al. 2015)
Appendix 3
Table A3.1. Ab initio estimate of the tungsten endowment of Variscan ...
Table A3.2. Estimate of tungsten reserves and resources in Variscan ...
Table A3.3. Inventory of samples used for the plates
List of Illustrations
Chapter 1
Figure 1.1. Rare earth elements in the periodic table of elements
Figure 1.2. Filiation of the successive discoveries of REEs
1
,
2
Figure 1.3. Global distribution of REE use by sector in 2018
Figure 1.4. The main applications for each REE (Bru et al. (2015) and referenc...
Figure 1.5. Evolution of prices for the main REEs
Figure 1.6. Global consumption and production of REEs between 2000 and 2020 an...
Figure 1.7. Imports, exports and trade balance of the European Union for REEs ...
Figure 1.8. Use of REEs in the European Union in 2016 (Sebastiaan et al. (2017...
Figure 1.9. Characteristics of the main deposit models
Figure 1.10. Distribution of different occurrences of REEs affiliated with end...
Figure 1.11. The alkaline complexes of Kola-Karelia (Kogarko 1987)
Figure 1.12. Khibiny alkaline intrusion (Arzamastsev et al. 2008)
Figure 1.13. Lovozero alkaline intrusion (Arzamastsev et al. 2008)
Figure 1.14. Kovdor alkaline intrusion (Verhulst et al. 2000)
Figure 1.15. Sokli massif in Finland (modified from Browne (2008))
Figure 1.16. Shear gneiss with REE-Nb-Zr at Otanmäki-Katajakangas, Finland (Sa...
Figure 1.17. REE magnetite-apatite iron ores of the type found in Kiruna (Swed...
Figure 1.18. P-REE and carbonatite complex in Siilinjärvi, Finland (Pusstinen ...
Figure 1.19. REE-Zr nepheline syenite at Norra Kärr, Sweden (Gates et al. 2013...
Figure 1.20. Nb-Zr-REE alkaline complex in Alnö (Sweden), modified from Vuorin...
Figure 1.21. Bastnäs type Fe-REE-(Cu) skarns, Sweden (Holtstam and Andersson 2...
Figure 1.22. Nb-REE-Fe and carbonatite complex at Fen-Søve (Norway), modified ...
Figure 1.23. Ta-Nb-REE pegmatite fields at Evje-Iveland, Froland and Glamsland...
Figure 1.24. U-REE-P phosphorite at Tåsjö (Sweden)
Figure 1.25. Pyroxenite and P-REE complex at Misværdalen, Norway (Ilhen et al....
Figure 1.26. Caledonian magmatism and associated alkaline intrusions (Halliday...
Figure 1.27. Welsh basin and Ce anomalies associated with gray monazite occurr...
Figure 1.28. Gray monazite shales from the Ordovician in the Ardenne, Belgium ...
Figure 1.29. Fe-Ti-REE apatite pyroxenite ores at Kodal (Ilhen et al. 2013)
Figure 1.30. Fluorine district in the Pennines (United Kingdom). GSV: Great Su...
Figure 1.31. Bauxite and Ni karsts of the Mediterranean belt (Promine and EURA...
Figure 1.32. Gray monazite paleoplacers and black shales in the Armorican mass...
Figure 1.33. British part of the North Atlantic Cenozoic igneous province
Figure 1.34. Kaiserstuhl Nb-Ta-REE alkaline volcanic complex, Germany (Weisenb...
Figure 1.35. REE occurrences in Greenland (Steensgaard et al. 2010; Charles et...
Figure 1.36. Deposits from the Paleoproterozoic at Karrat (NIAQ and UMIA) (Ava...
Figure 1.37. Alkaline province from the Mesoproterozoic at Gardar
Figure 1.38. Ilímaussaq complex including the Kvanefjeld and Kringlerne deposi...
Figure 1.39. Alkaline complexes at Motzfeldt and Grønnedal-Ika
Figure 1.40. Sarfartoq carbonatite (Secher et al. 2009)
Figure 1.41. Synthetic geodynamic section of Europe with the main types of REE...
Figure 1.42. Grade/tonnage relationship for the different types of localized r...
Figure 1.43. Global REE reserves estimated in 2015 (Bru et al. 2015)
Chapter 2
Figure 2.1. (a) Tectonic map of the wider European Variscan belt showing the s...
Figure 2.2. (a) Exposure of the Mawnan lamprophyre dyke, Cornwall, hosted by D...
Figure 2.3. (a) Sharp contact between coarse-grained porphyritic (G1a) and fin...
Figure 2.4. (a) Alkali feldspar phenocrysts defining magmatic state foliation ...
Figure 2.5. (a) Mafic microgranular enclave (MME) approximately 0.2 m across w...
Figure 2.6. (a) Elvan (quartz porphyry) dyke hosted by metasedimentary rocks a...
Figure 2.7. Geological map of the principal mineralogical and textural variati...
Figure 2.8. QEMSCAN false color images showing predominant granite mineralogy....
Figure 2.9. The range of biotite group mica compositions in the different gran...
Figure 2.10. Example geochemical plot of Zr versus Nb showing distinct groupin...
Figure 2.11. Average chondrite-normalized REE patterns for G1-G5 granites usin...
Figure 2.12. Multi-element plot showing average metal abundances normalized to...
Figure 2.13. (a) Pegmatite with large alkali feldspars at Megiliggar Rocks ass...
Figure 2.14. (a) Replacement deposit at Red-a-Ven, Dartmoor granite comprising...
Figure 2.15. (a) Sheeted greisen-bordered vein complex hosted by muscovite (G2...
Figure 2.16. (a) Gently-inclined Quartz Floor (quartz ± alkali feldspar ± wolf...
Figure 2.17. Examples of tourmaline-dominated veins and lodes. (a) Steeply dip...
Figure 2.18. QEMSCAN fieldscan image of polymetallic vein sample from undergro...
Figure 2.19. Schematic map representation of the progressive development and r...
Figure 2.20. (a) View over the Karslake complex, a number of smaller china cla...
Figure 2.21. The SW England resources sector and global tin price 1985–2019. A...
Figure 2.22. Drakelands W-Sn Mine open pit and processing plant looking SW (20...
Figure 2.23. (a) Location of deep geothermal energy projects superimposed on t...
Chapter 3
Figure 3.1. The regional context at Panasqueira (redrawn from Marignac et al. ...
Figure 3.2. Late kinematic D3 quartz veins (“Seixo Bravo” SB) at Panasqueira...
Figure 3.3. Map of the Panasqueira region
Figure 3.4. Section of the Panasqueira deposit (Kelly and Rye 1979; Bussink 19...
Figure 3.5. General aspect of the Panasqueira veins
Figure 3.6. Examples of automorphic minerals from the Panasqueira vugs
Figure 3.7. The anomaly halo associated with the Panasqueira deposit
Figure 3.8. The Panasqueira granitic suite
Figure 3.9. The alternative paragenesis by Carocci (2019) and Cathelineau et a...
Figure 3.10. Characterization of the stage III vugs sealed by the sulfides (II...
Figure 3.11. Examples of stage I wolframite mineralization. Wfm: wolframite
Figure 3.12. Examples of relationships between wolframite 1 and quartz I and t...
Figure 3.13. Stage III sulfides
Figure 3.14. The two generations of Panasqueira phosphates
Figure 3.15. Illustration of the geodic phenomenon
Figure 3.16. The zoning of the arsenopyrites: a representative example demonst...
Figure 3.17. Statistics of the sulfur and arsenic values of the Panasqueira ar...
Figure 3.18. Examples of relationships between arsenopyrite and stages I to II...
Figure 3.19. Example of a muscovite selvage developed later than the stage I q...
Figure 3.20. Late generations of tourmaline
Figure 3.21. Pyrrhotite pyritization stage (stage III-C) and its relationships...
Figure 3.22. Expression of siderite when not associated with the recrystalliza...
Figure 3.23. Some aspects of the late stages
Figure 3.24. Table of the available ages for the Panasqueira deposit
Figure 3.25. Flat joints and their relationships with vein systems
Figure 3.26. Tangential component indices in the opening of the Panasqueira ve...
Figure 3.27. The early fluid inclusions (FIs) and the complexity of the quartz...
Figure 3.28. Estimate of P–T-t conditions at Panasqueira between stages I and ...
Figure 3.29. Summary of data available on the composition of the Panasqueira f...
Figure 3.30. Isotopic compositions calculated from the fluids associated with ...
Figure 3.31. Model for the early stages of the Panasqueira hydrothermal and ma...
Appendix 3
Figure A3.1. History of paragenetic successions for the Panasqueira deposit
Figure A3.2. Variability of the muscovite selvages; the sulfurs are essentiall...
Figure A3.3. Examples of arsenopyrite selvages
Figure A3.4. Characterization of stage III geodes, clogged by sulfurs (III-B)
Figure A3.5. The beginning of stage III: aspects of the development of topaz
Figure A3.6. Topaz-wolframite association (Wfm3-III-A)
Figure A3.7. Locating the implantation of later stages through earlier structu...
Figure A3.8. Muscovite 1 and muscovite 2
Figure A3.9. Demonstration of a micro-stratigraphy in stage IV geodic aptites:...
Figure A3.10. Some aspects of changes in the wall rock at Panasqueira
Guide
Cover Page
Table of Contents
Title Page
Copyright Page
Begin Reading
Appendix 1: The Rare Earth Resources of Europe and Greenland: Mining Potential and Challenges
Appendix 2: The Cornubian Batholith: Post-Collisional Variscan Granites and Resources
Appendix 3: The Panasqueira W Deposit (Portugal): A Critical Bibliographic Review
List of Authors
Index
Summary of Volume 2
WILEY END USER LICENSE AGREEMENT
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SCIENCES
Geoscience, Field Director – Yves Lagabrielle
Natural Resources: Applied Basic Research,Subject Head – Philippe Boulvais
Metallic Resources 1
Geodynamic Framework and Remarkable Examples in Europe
Coordinated by
Sophie Decrée
First published 2023 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.
Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:
ISTE Ltd27-37 St George’s RoadLondon SW19 4EUUK
www.iste.co.uk
John Wiley & Sons, Inc.111 River StreetHoboken, NJ 07030USA
www.wiley.com
© ISTE Ltd 2023The rights of Sophie Decrée to be identified as the author of this work have been asserted by her in accordance with the Copyright, Designs and Patents Act 1988.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s), contributor(s) or editor(s) and do not necessarily reflect the views of ISTE Group.
Library of Congress Control Number: 2023935886
British Library Cataloguing-in-Publication DataA CIP record for this book is available from the British LibraryISBN 978-1-78945-135-1
ERC code:PE10 Earth System Science PE10_10 Mineralogy, petrology, igneous petrology, metamorphic petrology
1The Rare Earth Resources of Europe and Greenland: Mining Potential and Challenges
Nicolas CHARLES1, Johann TUDURI1,2, Gaétan LEFEBVRE1, Olivier POURRET3, Fabrice GAILLARD2 and Kathryn GOODENOUGH4
1BRGM, Orléans, France
2ISTO, CNRS, University of Orléans, France
3AGHYLE, UniLaSalle, Beauvais, France
4British Geological Survey, Edinburgh, United Kingdom
1.1. Introduction
In the past few years, 17 metal elements have absorbed the principal attention of industrialized countries, which are now aiming for a digital transformation and energy transition. Rare earths, which were little used in industry at the outset, are strategic metals today, a kind of vitamin for digital and green technologies (Bru et al. 2015; EC 2019a, 2019b; Blengini et al. 2020; Dushyantha et al. 2020). Used anecdotally in the 1950s and 1960s within heavy mineral placers in Australia, India, South Africa or Brazil, their attractiveness grew, and the United States became their main producer from the 1970s to 1980s with its Mountain Pass deposit.
At the end of the 1980s, China then became the main global producer of rare earths. In 1992, the first secretary of the Chinese Communist Party, Deng Xiaoping, was pleased to say that “the Middle East has oil; China has rare earths”. This is still the case for China today with its hegemonic position, which it owes to the use of gigantic deposits such as Bayan Obo, but above all to its expertise in rare earth separation.
At the outset, everyone seemed to accommodate this situation, with importing countries benefiting from the low price, while also avoiding the environmental and social impacts of mining these metals on their own territory.
It took a diplomatic incident involving a small island in the East China Sea for the whole situation to change in September 2010. China declared an embargo on the export of rare earths to Japan, a major importer of rare earths and a country at the forefront of digital technologies. Then, the lowering of Chinese export quotas lit the keg in 2011, with the rapid increase in the price of rare earths (as much as 10,000% for dysprosium).
Many countries were already aware of the vulnerability of their supply chain, principally in Europe (EC 2011, 2017; Sebastiaan et al. 2017; Lauri et al. 2018; Blengini et al. 2020). Rare earths were already strategic raw materials, and their criticality for European industry was classed as a priority. Therefore, for some years mining for rare earths benefited from investments intended for finding alternatives to the Chinese deposits.
In addition to the study of primary deposits (Goodenough et al. 2016; EURARE 2017; Tuduri et al. 2020), the recycling path was also considered (Ahonen et al. 2015; Guyonnet et al. 2015). It transpired that Europe and Greenland (a constituent territory of Denmark) had real potential for rare earth mining that could support the needs of the Old Continent for several decades, or even beyond. Europe was the continent where rare earths were discovered in 1787, but to date, there is no mine for these metals, and 95% of their imports depend on China (Gislev and Grohol 2018).
Geological potential is not all, however, and an entire value chain must be developed, from the extraction of the minerals, or rather of rare earth minerals, which require processing techniques adapted for each of them, to their transformation into high added value products (Ahonen et al. 2015).
It is here that the challenges begin, because the investments to be considered are colossal. In addition, what about the environmental, social and societal acceptability of mining activity in Europe? Although Europe has remarkable rare earth potential, can we envisage exploiting it? This original summary provides a panorama of rare earths in Europe through their physicochemical, mineralogical, socioeconomical, geodynamic and metallogenetic aspects.
1.2. The extreme diversity of rare earths
1.2.1. Rare earth elements
1.2.1.1. Definitions
“Rare earths” is a collective name given, for historical and practical reasons, to a set of metal elements in the periodic table (Figure 1.1). Rare earth elements (REEs) are elements called “trace elements” in most natural environments. REEs are a group of 17 metal elements that are coherent in terms of ionic rays, charge and coordination. According to the definitions (Henderson 1984; Lipin and Mckay 1989; Jones et al. 1996; Atwood 2012), the REEs include lanthanides (from 57La to 71Lu), yttrium (39Y) and sometimes scandium (21Sc).
Scandium’s membership in this group has given rise to debate since its behavior in geological environments is generally different from that of the other REEs. Similarly, promethium (61Pm), with its extremely short half-life, is almost non-existent in nature.
Depending on the specific electron configurations within each atom, the REEs can be divided into two subgroups:
the light rare earth elements (LREE) with La-Ce-Pr-Nd-Sm-Eu-Gd;
the heavy rare earth elements (HREE) with Tb-Dy-Ho-Er-Tm-Yb-Lu-Y.
It should be noted, however, that the membership of some REEs to one of the two subgroups is still debated (Gupta and Krishnamurthy 2005; Chakhmouradian and Wall 2012; McLennan and Taylor 2012; Weng et al. 2013; Zepf 2013). There is therefore a classification specific to the mining industry that differs from that recommended by the International Union of Pure and Applied Chemistry (IUPAC). For economic reasons linked to geological abundance, to the costs of processing the ore, to separation techniques, etc., many actors in the mineral industry only consider these as LREE: La-Ce-Pr-Nd.
These same industrial actors separate and sell their concentrations of rare earths in the form of oxides, and it is usual to consider these elements in terms of rare earth oxides (REO). Thus, the terms light rare earth oxides (LREOs) and heavy rare earth oxides (HREOs) are generally considered over the course of any value chain, from mining exploration to their separation, by mining extraction.
Figure 1.1.Rare earth elements in the periodic table of elements
1.2.1.2. The physical and chemical properties of the rare earths
The REEs have physical-chemical properties much sought after by manufacturers, thanks in particular to their internal electron structure linked to their 4f electron subshell. The REEs in neutral metallic form have fairly similar atomic radii, except for europium and ytterbium, whose larger atomic radii explain their lower densities. Their hardnesses are variable, ranging from soft (La, Nd, Yb) to hard (Ho, Er, Lu).
The REEs are moderately fusible, and their fusion temperatures range between 799°C (Ce) and 1,663°C (Lu). The spectral properties of REEs are most remarkable for absorption (coloration), as well as for transmission (luminescence), which explains their current use in phosphors and lasers. It is the electrons’ level of mobility in the atoms’ energy levels that forms the basis of this property. Subject to powerful rays (e.g. UV rays), an REE atom surrounded by ligands (oxides or molecules) will be excited electronically, and de-excitation of the REE atom will result in the emission of light with wavelength emission peaks specific to the REE element (e.g. Y and Eu: red and blue; Tb and Tm: green; Ce: yellow).
The other remarkable physical property of some REEs is their magnetism, which is the origin of their use for making high-performance permanent magnets (high magnetization and remanence). REEs paired with transition elements (Fe, Co) allow the creation of the most coercive magnets manufactured at the industrial scale (Sm-Co, Nd-Fe-B).
From a chemical point of view, REEs are reducing metals (deoxidation and desulfurization properties). Most take between a few days and a few months to oxidize rapidly in air and at ambient temperature (Eu, La, Ce, Pr, Nd). The HREEs resist oxidation for several years (Y, Dy, Ho, Er). Finely ground, Ce allied with Fe (ferrocerium) burns in air. This was one of the first applications of REEs with flint-spark-lighters formed of ferrocerium. In minerals, REEs are in trivalent cation form. Although the ionic radius varies from one rare earth to another, their chemical properties remain remarkably homogeneous, especially in solution. Although many substitutions between REEs are produced within the crystalline network of minerals, some mineral species are better adapted and more favorable to receiving a range of ionic radii. This is the case with “ceric earth” minerals, which are more inclined to incorporate Ce, La, Nd, Pr, (Sm), (Eu) and (Gd), such as monazite and bastnäsite. Other minerals called “yttric earths” are more favorable to Y, Tb, and Dy, such as xenotime and gadolinite.
1.2.1.3. A brief history of rare earths
The discovery of rare earths began in 1787 in Sweden. Remember in passing that the word “earths” was the name given by chemists to the metal oxides supposed to be simple bodies. The epithet “rare” recalls the difficulties encountered by chemists in isolating them and their supposedly low concentration in ores. Carl Axel Arrhenius, a Swedish chemist, described for the first time a dense, black mineral in the pegmatites of Ytterby. They were sent for analysis to the Finnish chemist Johan Gadolin. In 1794, he discovered a new “earth” contained in this mineral, yttria, which would give its name to ytterbite, since it was known by the name gadolinite. However, a reddish mineral was discovered earlier, in 1751, by the Swedish mineralogist Axel Fredrik Cronstedt in the copper mine at Bastnäs. It was only in 1803 that the Swedish chemists Jöns Jakob Berzelius and Wilhelm Hisinger isolated a new “earth” with properties similar to yttria. This new earth was called ceria, a reference to the asteroid Ceres that had just been discovered, and would give its name to the mineral bastnäsite.
Throughout the 19th century, different chemists discovered that some previously isolated earths actually contained several other chemical elements with similar properties. For example, in 1839, Carl Gustaf Mosander discovered that cerium oxide is also formed of an oxide of another element that he would call lanthanum (from the Greek lanthano: to be hidden). In 1843, he discovered that ytterbium was in fact a mixture containing two other elements, terbium and erbium. The final REE element, lutetium, was discovered in 1907. Finally, it should be noted that promethium was discovered in 1947 in uranium fission products from the Oak Ridge reactor (United States).
REEs were thus discovered by gradual separation, some from cerium (ceric earths) and others from yttrium (yttric earths). It should be noted that gadolinium would be identified in both types of earth. In order of discovery (Figure 1.2): Y (1794), Ce (1803), La (1839), Er (1843), Tb (1843), Sc (1876), Yb (1878), Ho (1879), Sm (1879), Tm (1879), Gd (1880), Nd (1885), Pr (1885), Dy (1886), Eu (1901), Lu (1907) and Pm (1947).
Figure 1.2.Filiation of the successive discoveries of REEs1,2
1.2.2. Rare earth minerals
From a geological point of view, REEs are not rare. Their natural abundance in the Earth’s crust is at least equivalent to that of other base metals (Zn, Cu, Pb, Ni, Co) and much less rare than previous metals (Ag, Au). On the other hand, although LREEs are the most abundant, they are found at some of the highest concentrations in numerous primary deposits. Conversely, the HREEs are clearly less abundant, much like the rare metals (Sn, W, Ta) and are therefore much rarer, including in deposits of these elements (except Y). For this reason, HREEs are considered to be more strategically important than LREEs, hence their much higher market value. Thus, the HREO/LREO ratio is a critical parameter for evaluating a deposit.
In fact, it is the low quantity of natural minerals containing REEs that explains the term “rare”. Although more than 200 REE mineral species are known today (this number remains low), only some of them (Table 1.1) are of commercial interest (Gupta and Krishnamurthy 2005). In fact, although REEs are often incorporated into the crystal lattice of carbonates, oxides, silicates or even phosphates as a substitution for other more common chemical elements, the mineral industry values only a very small number of REE ores: bastnäsite (fluorocarbonate), monazite and xenotime (phosphates), and loparite (oxide). REEs have also been extracted from apatite in Russia and South Africa, but this production was extremely limited.
Except for xenotime, which is enriched with HREEs, all of these minerals are essentially characterized by their richness in LREEs. Since lanthanides share similarities with elements from the actinide group, the REE minerals also and almost systematically include radioactive elements (e.g. Th and/or U). Uraninite, as well as thorite may also accompany REE minerals. The presence of these radioactive elements is a restriction on mining project development. In fact, radioactivity accompanies every stage of the ore enrichment process, right up to metallurgy. These minerals and radioactive elements are a form of waste that must be managed rigorously. For these reasons, it is necessary to focus on the U and Th contents in deposits, particularly on the ThO2/REO and U3O8/REO ratios of the minerals that form the ore.
Extracted from the main Chinese mines of Bayan Obo, Maoniuping Weishan and Dalucao, as well as from the Mountain Pass mine in the United States, bastnäsite is the main REE ore (Verplanck et al. 2016; Jia and Liu 2020). Since the 1970s, so-called ionic clays, or lateritic ion-adsorption clays, have formed an important source of HREEs (Bao and Zhao 2008). This production, located uniquely in southern China in Longnan (Jiangxi), but also in the provinces of Guangdong and Guangxi, is favored because of the low cost of labor and relatively simple extraction procedures using in situ lixiviation with neutral or acidic solutions.
However, with extremely low ore grades or 0.03–0.35% REO (Chi and Tian 2008; Zhou et al. 2017), such procedures question the balance between economic feasibility and protection of the environment. Nevertheless, the high proportion of HREEs coupled with the very low concentration of radioactive elements (U, Th) associated with this type of deposit make it an attractive challenge in mineral exploration.
Table 1.1.Minerals valued by the extraction industry (Tuduri et al. 2015)
Mineral
Chemical formula
Concentration (%)
RE
2
O
3
ThO
2
UO
2
Allanite
([REE],Ca)
2
(Al,Fe)
3
Si
3
O
12
(OH)
2.5–17
<3
–
Ancylite
Sr[LREE](CO
3
)
2
(OH).H
2
O
46–53
<0.4
<0.1
Apatite
Ca
5
(PO
4
)
3
(F,Cl,OH)
<<2
–
<0.05
Bastnäsite
[LREE]CO
3
(F,OH)
58–75
<2.8
<0.1
Clays
REE adsorbed on kaolinite/halloysite Al
2
Si
2
O
5
(OH)
4
<<4
<0.01
<0.001
Eudialyte
(Na,[REE])
15
(Ca,[REE])
6
(Fe,Mn)
3
(Si,Nb)
2
(Zr,Ti)
3
Si
24
O
72
(OH,F,Cl,H
2
O)
6
1–10
–
<0.1
Euxenite
([REE],U,Th)(Nb,Ta,Ti)
2
O
6
16–30
<4.3
3–9
Fergusonite
[REE]NbO
4
43–52
<8
<13.6
Gadolinite
[REE]
2
FeBe
2
Si
2
O
10
45–54
<0.4
–
Loparite
(Na,[LREE],Ca,Sr,Th)(Ti,Nb,Ta)O
3
28–37
1.6
0.03
Monazite
([LREE],Th,Ca)(P,Si)O
4
35–71
<20
<16
Parisite
Ca[LREE]
2
(CO
3
)
3
F
2
50–59
<4
<0.3
Pyrochlore
(Ca,Na,U,[REE])
2
(Nb,Ta)
2
O
6
(OH,F)
<22
<4
<27
Steenstrupine
Na
14
[LREE]
6
Mn
2
Fe
2
(Zr,Th)(PO
4
)
7
Si
12
O
36
.3(H
2
O)
<31
<6
<1
Thorite
(Th,U,[REE])SiO
4
<3
65–81
10–16
Uraninite
UO
2
<1.5
<12.2
50–98
Xenotime
([HREE],Zr,U)(P,Si)O
4
54–74
<8.4
<5.8
Zircon
(Zr,[HREE],Th,U)SiO
4
<19
0.01–0.8
0.01–4
The last decade has seen the emergence of a substantial market for the exploration of REEs, intended to find resources outside of China. Although different projects are in the process of valuation, many of them are innovative projects since they are not conventional and thus present economic risks. Some projects correspond to new deposit models, and others seek to develop new minerals: pyrochlore, fergusonite, oxides and numerous silicates (e.g. allanite, eudialyte, steenstrupine). These mineral stages, especially silicates, have the advantage of being enriched with HREOs.
1.3. The economy of rare earths in the world and their place in Europe
1.3.1. The application domains for rare earths
The first use of REEs was attested in 1885, when cerium was used in gas sleeves in the city of Vienna. The usage of REEs was very limited until the 1960s (ferrocerium in lighter flints), then more diversified with applications in technology from the 1970s (color cathode screens, lasers, phosphors, etc.) and 1980s (permanent magnets).
REEs have exceptional magnetic, electronic, optical and catalytic properties, and are particularly useful today for ever more diversified, well-developed technologies, especially in the defense industry, electronics and renewable energies (Figures 1.3 and 1.4) (Balaram 2019; Dushyantha et al. 2020). REEs are used in different chemical forms: metals, alloys, oxides and chlorides.
Figure 1.3.Global distribution of REE use by sector in 2018
Figure 1.4.The main applications for each REE (Bru et al. (2015) and references therein; Sebastiaan et al. (2017))
REEs made it possible to increase the performance of technological products, while still ensuring miniaturization, such as with magnets, and they deserve the name “the vitamins of modern industry” (Balaram 2019). For some years, REEs have excited additional interest in their use in manufacturing green technologies (wind turbines, solar panels), which are indispensable for ensuring energy transition (Judge et al. 2017). Thus, the use of Pr, Gd, Eu and Er in nanoparticle form in solar panels makes it possible to improve the capacity to convert photons into energy. Pr, Nd, Tb and Dy are used in permanent magnets in wind turbines and allow them to be lightened drastically (a 100 g NdFeB magnet is equivalent to a 1 kg traditional magnet), also allowing the miniaturization of the engine, while still ensuring increased performance, even at low wind speeds, as well as reduced maintenance.
Nevertheless, the market volatility of REE has led substitution elements to be found (Bru et al. 2015; Pavel et al. 2017). Other less well-known REE domains are zootechnics and agriculture since REEs play an essential role in the working and structure of the molecules of biological systems, especially La and Ce (Abdelnour et al. 2019). REEs are thus incorporated into animal food and fertilizer. REEs can also be used for military purposes, in the form of effective permanent magnets (SmCo, NdFeB), useful in guiding systems for missiles, fighter planes and drones, or for on-board electrical engines. Tb, Er and Gd are useful for night vision optical lenses. Y is used in the manufacture of highly resistant ceramics (tanks, bullet-proof vests). Eu and Lu allow radar signals to be amplified or are useful in sonar detection.
The sectors where REEs are used have evolved extensively since 2010, the year of the global crisis triggered by the restriction of Chinese exports and a momentary drop in global consumption (Bru et al. 2015). Since 2012, the growth of this consumption has resumed and exceeded 100,000 t REO (Figure 1.6), particularly due to the permanent magnet sector. The main technology used is NdFeB magnet technology, using Nd and Pr in particular and, to a lesser extent, Dy and Tb for high-performance applications. The application that consumes the most REEs globally is NdFeB magnets, with approximately 30% of REE use in tonnage in 2018 and nearly 53% of the total value of the REE market. This demand is increasing by 10% per year. There are multiple sectors for the use of these magnets, such as the domain of high-efficiency electrical engines, where they allow miniaturization (electronics, robotics), and lightning of equipment (offshore wind farms, electrical vehicle engines, etc.)
Other sectors using REEs are becoming a minority in proportion (Bru et al. 2015), either due to restricted or specific uses (the defense industry, medical lasers, etc.), or on the contrary, usage with low added value for applications where performance is of less importance (polishing powders catalysts in cars, metallurgical alloys).
1.3.2. The evolution of prices
There is a great disparity between the price of LREEs, which are very abundant, and that of HREEs, which are reserved for niche applications because of their rarity. These prices thus range from single to triple digits or more depending on the elements (Figure 1.5).
These prices have also varied greatly over time, with prices multiplying by several dozen between 2002 and 2003, reaching a peak in July 2011, before a great drop, then a new and relative equilibrium after 2015. The very sharp rise in the prices of all REEs began at the start of 2010, was amplified after February 2011, and reached its height in mid-July 2011. On July 14, 2011, the price of dysprosium-metal reached 3,410 US$/kg, a multiplication by a factor of 106 compared to the average price of this metal from 2002–2003 (then, it was 32.1 US$/kg), which is an increase of 10,500%, which is probably an absolute record for all raw materials combined.
The sky-rocketing of prices in 2010–2011 was triggered by the conjunction of two main factors:
the decision to reduce Chinese export quotas considerably (these exceeded approximately 60 kt from 2006–2007, 57 kt in 2008, 50 kt in 2009 and then 30 kt/year from 2010);
the increase in demand (after a marked drop in 2009 in the context of the slump following the economic crisis) and in anticipation of furthering this increase, particularly for permanent magnets (the push for renewable energies, including wind power; anticipating, at that time, the striking take-off of the electric vehicle market, etc.), and phosphors (the increasingly widespread replacement of incandescent bulbs by compact fluorescent bulbs).
The incident at the Senkaku/Diaoyu Islands, in September 2010 between China and Japan, led China to declare an embargo on the export of REEs to Japan in October 2010. Cited by many as the trigger for the spike in the price of REEs, this event, in reality, only accentuated the rise in prices that had already begun several months before and that continued for several months afterwards. Threats to world supplies outside China following this event led manufacturer-users to buy to create preventive stocks, thus contributing to a price increase, the whole accentuated by a speculative factor. Following a classical “bubble” mechanism, soaring prices led to a drop in demand (Figure 1.6). This drop in consumption led to the “bursting” of this bubble and a near-continuous fall in prices for two years (between mid-2011 and mid-2013).
After occasional rises in 2014 and 2017 linked to imbalances in supply and demand and the effect of advertising (Lefebvre 2017), the prices of different REEs remained at almost unchanged levels until 2020. Expressed in metal form at 99% FOB China, La and Ce remained at almost unchanged levels in 2018 and 2019, at 6 $/kg on average. The price of Tb, then more expensive than REEs, became established at approximately 600 $/kg, whereas Dy is exchanged at 250 $/kg on average. Finally, the prices of Nd and Pr have stabilized today at 55 $/kg and 100 $/kg, respectively (compared to 85 $/kg on average from 2016 and 2017 for Pr, illustrating its growing role in permanent magnets).
The health crisis linked to the global Covid-19 pandemic had a limited impact on the rare earths market in China. Although 70–80% of rare earth transformation capacities underwent temporary interruptions in January and February 2020, linked to lockdown (in particular, capacities for processing HREEs in the southern regions, of the provinces of Jiangxi and Guangdong, close to the city of Wuhan), most of them were already functioning at less than full capacity or involved illegal or obsolete sites. There was therefore excess capacity in the country for the production of rare earths, which limited the impact of the health crisis on the sector. Only dysprosium and terbium, the HREE elements involved in high-performance, permanent NdFeB magnets (in temperature conditions higher than 200°C), saw high prices between January and March 2020: 15.5% for metal terbium (762 $/kg) and 20% for metal dysprosium (372 $/kg), respectively, reflecting the low stocks available rather than an underlying trend.
The increase in demand linked to the take-off in sales of electrical vehicles and renewable energies, faced with limitations mine in Chinese production capacities (Figure 1.6), could lead to a new rise in prices between now and 2025. On average, demand for REEs is progressing from 8 to 10% per year and should continue at this rate, driven by the rise in electrical vehicles, as well as by the rise in electronics and robotics. At such a rate, global REE consumption could double in less than 10 years.
Figure 1.5.Evolution of prices for the main REEs
(source: BRGM)
The case of electrical vehicles is eloquent. Although sales were in the order of two million units in 2018, many scenarios predict an exponential increase in 2030 between 20 and 38 million/year, as estimated by the International Energy Agency (New Policies Scenarios and EV30). Indeed, according to data from the consultant Roskill (2018), 90% of new electric vehicles are equipped with engines using permanent REE magnets (dominated by Chinese models, but also Tesla for its Model 3 Long Range) compared to induction motor technology, chosen especially by BMW to eliminate the need for REEs. Consequently, with an average value of 2 kg of permanent magnets mounted on each vehicle, which is 750 g of Nd-Pr alloy, this new market would reach between 15,000 and 28,500 tons of Nd-Pr allowance, compared to 3,000 tons in 2018.
Figure 1.6.Global consumption and production of REEs between 2000 and 2020 and estimates between 2021 and 2025
(source: BRGM)
1.3.3. Europe in the rare earth economy
Europe consumes 10% of the REEs produced in the world. Moreover, this is one of the most promising markets for the development of electrical mobility and for the installation of offshore wind farms. Legitimate questions arise about potential sources of REEs to ensure their needs. In 2018, global production was estimated at 170,000 t REO. This figure represents a low range, since only official Chinese government quotas are considered (120,000 t in 2018, an increase of 14% compared to 2017), and not the country’s illegal production (estimated between 40,000 and 50,000 tons). China’s contribution to global production should comprise between 70 and 90% according to estimates.
Vertical integration of the whole REE production chain up to permanent magnets is one of China’s major competitive advantages and raises the important question of the vulnerability of supplies for the European industry (Figure 1.7), not only of the raw material, but also of the products that are derived from it (Figure 1.8). To attenuate the concomitant industrial risks, the EU is encouraging the United States to develop and diversify their supply sources, whether primary (mining) or secondary, thanks to reuse, recycling and waste reduction (Guyonnet et al. 2015; Rollat et al. 2016).
Figure 1.7.Imports, exports and trade balance of the European Union for REEs (metals, alloys and compounds) expressed in weight (kt-thousands of tons) and in value (M€-million euros) between 2002 and 2019
(source: Eurostat). Codes CN8 no. 2846 and 280530
One of the main challenges for the European continent, beyond commissioning these deposits, is to develop expertise in transforming REEs at the separation and refining stages, inspired by recent dynamics from Australia and the United States.
Thus, the Australians declared some projects as being of “national interest” and confirmed in March 2020 the desire to form part of a financial consortium for the development of the Dubbo project in New South Wales (Alkane 2020). In July 2020, via the Pentagon, Americans announced 40 million US$ worth of financial assistance to build two heavy rare earth separation factories on American soil (Scheyder 2019, 2020).
Figure 1.8.Use of REEs in the European Union in 2016 (Sebastiaan et al. (2017) and references therein)
1.4. Classification of rare earth deposits
REE deposits can be divided into two major categories (Figure 1.9):
– primary or endogenous deposits associated with magmatic and hydrothermal processes;
– secondary exogenous deposits linked to sedimentation and/or climatic processes (Walters et al. 2011; Chakhmouradian 2012a, 2012b; Charles et al. 2013; Tuduri et al. 2015; Goodenough et al. 2016; Dushyantha et al. 2020). Despite the great variety of deposits, only three types are in use:
- carbonatites (48% of production globally),
- alkaline magmatism deposits (2%),
- ionic clay deposits (36%),
- lateritic deposits (12%),
- placers (2%).
Figure 1.9.Characteristics of the main deposit models
COMMENT ON FIGURE 1.9.–In blue, the major deposits located in Europe or Greenland. T: tonnage; *the 8% value corresponds to the Mount Weld deposit, and the corresponding HREO/LREO ratio is 0.3. Active mines are marked with a mining symbol. Bastnäs is a part of mining heritage. Abbreviations: AU (Australia), BR (Brazil), CA (Canada), CN (China), FI (Finland), GL (Greenland), GR (Greece), IN (India), RU (Russia), SE (Sweden), TR (Turkey), US (United States), ZA (South Africa).
1.4.1. Primary endogenous deposits
REE carbonatites are characterized by intrusive bodies formed of carbonate rocks that are low in silica (< 10% weight SiO2), but often enriched in REEs and accompanied by additional Nb, Ba, Sr, F, U, Th, Ti, Zr, and P minerals, as well as base metals (Cu, Pb, Zn). The carbonatites generally have REO levels above 1% and may exceed 5%, as in Bayan Obo (China) or the Mountain Pass mine (United States). Enrichment with REEs is marked by LREE levels in bastnäsite, monazite, apatite and allanite. The HREO/LREO ratio is low and generally below 0.1 (Figure 1.9).
REE deposits may also be associated with the alkaline complexes formed by magmatic alkaline rocks, generally undersaturated and moderately enriched with silica (35–60% weight SiO2). These types of rocks (e.g. nepheline syenite) are characterized by an abundant and rich mineralogy that, in addition to REEs and Nb, are enriched with Zr, Ta, Be, Ti, Li, U and Th.
In contrast, REE levels associated with alkaline complexes are lower than those in carbonatites and generally < 2% (e.g. Norra Kärr in Sweden and Kringlerne in Greenland at 0.6% REO). These types of deposits are frequently enriched in HREEs (in comparison to carbonatites). Therefore, the HREO/LREO ratio, although it is generally very variable, is generally > 0.15 and sometimes > 1. The main, useful minerals are loparite, eudialyte, gadolinite or even steenstrupine and are often associated with the names of “exotic” rocks (ijolites, lujavrites, kakortokites, urtites or melteigites, etc).
Rifts in cratonic domains are zones with great economic potential, such as the Baltic shield, which includes the Kola Peninsula in Russia and Greenland (Goodenough et al. 2016). Only the loparite alkaline complexes of the Kola Peninsula are exploited today for their REEs and represent only 2% of global production. Although they are underused, alkaline complexes are the essence of new projects for exploring REEs. In 2015, Norra Kärr (Sweden) was the first deposit situated in the EU to certify resources and reserves evaluated at almost 55 Mt at 0.55% REO. Other deposits linked to alkaline intrusions show great potential. Moreover, the Khibina and Lovozero complexes in the Kola Peninsula include reserves estimated at more than 2 Gt at 0.6% REO. In southern Greenland, the magmatic province of Gardar is probably the most extraordinary. It is an ancient rift (1.35–1.12 Ga) over which a large number of alkaline complexes have been made (Grønnedal-Ika, Igaliko, Ilímaussaq, Nunarssuit or Tugtutôg) and has great potential since all have REE minerals, but also Nb and Zr ± U. Each intrusion contains a potentially world-class deposit such as the Ilímaussaq complex, including the Kvanefjeld and Kringlerne deposits. These alkaline complexes are mainly formed of nepheline syenite, associated locally with carbonatites. Concerning deposits associated with carbonatites, Norway, Finland and the Kola Peninsula in Russia have the greatest potential. The main REE-bearing minerals are apatite, bastnäsite, monazite and pyrochlore, and sometimes allanite, parisite and ancylite. The main targets are Fen in Norway (83.7 Mt at 1.08% REO), and there are many occurrences in the Kola Peninsula in Russia, such as Kovdor, which includes REO levels between 0.001 and 0.09% for an average tonnage of 500 Mt. In some deposits, substantial accumulations of apatite can form massive (apatitite) bodies within carbonatites. This is the case with the carbonatites at Siilinjärvi and Sokli (Finland), which, with 200 Mt of apatite reserves, could also form an important target for prospecting REEs. Indeed, Decrée et al. (2020) have recently demonstrated that the extraction of the rare earths contained in apatite from carbonatite at Siilinjärvi (Finland) would represent a tonnage of between 133,000 and 161,000 tons REO.
In less conventional form, the famous mine at Ytterby in Sweden (Romer and Smeds 1994) belongs to the NYF pegmatite model (Nb, Y, F). Similarly, it makes sense to distinguish deposits associated with skarns (e.g. Bastnäs).
1.4.2. Secondary exogenous deposits
Secondary deposits represented the major part of REE production before the 1970s, with the exploitation of monazite placers. Today, secondary deposits can be subdivided into two groups: deposits associated with surface processes and belonging to the regolith type and basin deposits associated with sedimentary environments (Figures 1.9 and 1.10).
Surface processes, including hydrolysis, oxidation, hydration, or indeed decarbonation reactions, trigger a chemical change in rocks and minerals in addition to physical phenomena. Thus, the soluble elements (Mg, Ca) are partly or sometimes entirely leached in very aggressive climates. The insoluble elements (Fe and Al, which form part of the REE group) remain in place to recombine into neoformed minerals, mainly clays, hydrophosphates or carbonates. In the context of laterite, the weathering of rocks initially rich in REEs (e.g. carbonatite) will therefore produce secondary, still richer REE deposits. This is the case with the REE laterite deposit at Mount Weld (Australia), which developed at the expense of a carbonatite deposit, the exploited content of which is higher than 8% (Lottermoser 1990). Ionic clay deposits (ion-adsorption laterite clays) are associated with the weathering of granites. REEs with weak solubility are adsorbed to the surface of neoformed clays (halloysite/kaolinite). These deposits are certainly numerous, but they are very small in size (some tens of thousands of tons) and are exploited despite their very low content levels. Southeastern Europe has many REE occurrences associated with weathering processes and linked to bauxites and laterites. These occurrences offer potential that remains to be ascertained in the Balkans and in Greece (Grebnik, Nazda-Vlasenica, Marmara).
Sedimentary basins, placer-type deposits, are accumulations of heavy minerals in sand and gravel separated by the process of gravity during their transportation by water or wind. Diagenesis consolidates these placers, transforming them into paleoplacers. The main REE-bearing minerals are monazite, xenotime, fergusonite, euxenite and allanite. These deposits represented the greater part of REE production before the 1970s, in particular through the exploitation of monazite placers. They are still exploited (2% of global production in 2018). Another accumulation process of microorganisms and algae in a marine setting at this time can, via diagenesis, produce concentrations of phosphates called phosphorites. These rocks, enriched with apatite can, in some settings, include REEs (e.g. Tåsjö in Norway). Finally, concerning authigenic deposits, the diagenesis of some silico-clastic rocks enriched with organic matter can in some cases, under the effect of a raised temperature, produce notable concentrations of REEs (Donnot et al. 1973; Pourret and Tuduri 2017).
In Europe, secondary paleoplacer-type deposits are generally of Cenozoic age, even though some date back to the Precambrian (e.g. the Nordkinn Peninsula in Norway). The main mineral encountered is monazite, sometimes with xenotime, allanite, apatite, euxenite, fergusonite, loparite and zircon. In Western Europe, these paleoplacers are mainly characterized by gray monazite enriched with intermediate REEs (Sm-Eu-Gd) and with very low concentrations of U and Th. These monazites result from the erosion of sedimentary rocks from the ancient basins of the Lower Paleozoic in Western Europe (France, Wales, Belgium, Czech Republic, Iberia). They remain small in size and without economic interest (Donnot et al. 1973; Tuduri et al. 2013). The phosphate sandstones of the Ordovician are also interesting targets, for example, Tåsjö (Sweden).
Like some deposits of sedimentary phosphates in the United States (Emsbo et al. 2015), deposits of oolitic iron and phosphate ooids in Norway, Sweden or Estonia (Sturesson 1995) and phosphate chalk at Ciply in the Mons basin in Belgium (Jacquemin 2020) may also form potential targets for the exploration of rare earths in Europe (see Decrée et al. (2017) and references therein).
1.5. Rare earths deposits in Europe
From analyzing the geographical distribution of REE deposits, it seems that they are present at all stages of the rock cycle. Indeed, REEs are often associated with metamorphism, plutonism, metasomatism, hydrothermal processes and sedimentary environments. Moreover, Fedele et al. (2008) argue that the large-scale distribution of REE deposits across Europe has a geogenic origin as their source. Goodenough et al. (2016) argue that the main economic REE deposits in Europe are linked to areas of intracontinental rifting. Their varied geological settings are the result of a region’s evolution through geological time periods.
Thus, Europe and Greenland display extremely varied geological settings and include lithospheric blocks of varied nature that were assembled over the course of a geological history stretching back 3.8 billion years (see Choubert and Faure-Muret 1976; Ager 1980; Auboin 1980; Ziegler 1990; Asch 2003; Plant et al. 2005; Gee et al. 2008; Henriksen et al. 2009; Cloetingh et al. 2010 and references therein for a review).
The European continent has resulted from a long geological history over 3.6 billion years, with the assembly of many continental blocks. The European lithosphere can be divided into two distinct parts:
an ancient cold craton (the East European craton, EEC) partially covered by a weakly deformed covering from the Phanerozoic and strewn with rifts from the Meso-Neoproterozoic in Eastern Europe;
a thinner and cooler lithosphere dating mainly from the Phanerozoic and accreted to the craton during the course of the Paleozoic, including younger orogens in Western Europe (
Figure 1.10
) (Gee et al. 2008).
Figure 1.10.Distribution of different occurrences of REEs affiliated with endogenous and exogenous processes in Europe (Charles et al. 2013; Goodenough et al. 2016; EURARE 2017; Tuduri et al. 2020)
On the eastern flank of the craton, the Paleozoic orogeny of the Ural Mountains marks the boundary with Asia. To the north of Europe, the craton is surrounded by the Caledonids and the Timanids. Conversely, the southern border of the craton is less well defined since the evidence of accretions from the Neoproterozoic and the Paleozoic is partially obliterated by Alpine deformations and uplift, particularly well expressed in the Caucasus.
Finally, the western border of the craton is characterized by a major boundary of lithospheric scale, called a “Trans-European Suture Zone, TESZ” (Teisseyre 1903; Tornquist 1908; Thybo et al. 1999, 2002), stretching from the Black Sea to the North Sea. Thus, the TESZ separates the Precambrian lithosphere (EEC) to the east (e.g. the Baltic or Fennoscandian shield, the Ukrainian shield, and the Voronech massif) from the Phanerozoic lithosphere to the west. The latter is formed of land accreted during the Caledonian orogeny (e.g. Scandinavian, Irish-Scottish, German-Polish Caledonides) to the north, the Variscan orogeny (e.g. the French Massif Central, Bohemian massif, Armorican massif, Iberian massif) in the center, and the Alpine orogenies (e.g. the Alps, Pyrenees, Carpathians, Dinarides, Apennine, Betics) to the south.
1.5.1. Rare earth indices in the Baltic shield
1.5.1.1. Kola-Karelia Peninsula
The Kola-Karelia Peninsula includes a remarkable set of alkaline and hyperalkaline rocks (Figure 1.11) (Kogarko 1987). This area can be subdivided according to:
rocks from the Neoarchean age (2,750–2,600 Ma), including the Keivy complex;
rocks from the Paleoproterozoic age (1,900–1,600 Ma), including the Gremyakha-Vyrmes and Yeletozero intrusions (Arzamastsev et al. 2005);
rocks from the Paleozoic age (370 Ma), such as the Khibina, Lovozero or Sokli massifs (Vartiainen and Woolley 1976; Kramm and Kogarko 1993; Arzamastsev et al. 2008).
All these massifs are composed of rocks that contain REE minerals (e.g. apatite, loparite, eudialyte and ancylite) and can constitute future deposits.
1.5.1.1.1. Neoarchean Keivy province (2,750–2,600 Ma)
The alkaline intrusions from the Neoarchean are situated in the western part of the Keivy greenstone belt. The alkaline province of Keivy is formed by six hyperalkaline granite laccolites that date back to 2,750 to 2,600 Ma for a surface of approximately 2,500 km2 and two massifs of nepheline syenite injected along a fault on the border of the Keivy “terrane” (Mitrofanov et al. 2000; Zozulya et al. 2005, 2013).
Figure 1.11.The alkaline complexes of Kola-Karelia (Kogarko 1987)
These massifs include six lithological groups: aegirine-arfvedsonite granites, ænigmatite-arfvedsonite granites, lepidomelane-arfvedsonite granites, lepidomelane granites, aegirine-magnetite granites and ferrohastingsite-lepidomelane-aegirine-augite syenogranites. The granites are enriched with Zr, REE, Nb and Ga, the main bearing minerals of which are zircon, monazite, britholite-(Y) and fergusonite. The known occurrences are pegmatitic veins (elskoozerskoe) present in microcline-albite-quartz mineralized zones within alkaline granites (jumperuaiv) and in albitized and zeolite zones in contact with nepheline syenites (Sakharjok 1984; Belolipetskyi et al. 1992; Korsakova et al. 2012; Zozulya et al. 2012). Little exploration work has yet been done, but – given the surface of this province – the potential for mining discovery is real (Korsakova et al. 2012).
Zr-REE alkaline complex at Sakharjok (Russia)
The mineralized zone at Sakharjok (5–6 km2) is situated in the center of a hyperalkaline complex at western Keivy formed of a nepheline and phlogopite gabbro, a ferrohastingsite-lepidomelane syenite and an aegirine-lepidomelane nepheline syenite (Batieva and Bel’kov 1984; Zozulya et al. 2012). The ferrohastingsite-lepidomelane syenite is situated to the west and southwest of the complex, while the nepheline syenite occupies the eastern part. Zr-REE mineralization is linked to these two intrusions, which date back to between 2,682 and 2,613 Ma. The Sakharjok index consists of parallel veins within albitized nepheline syenite (Batieva and Bel’kov 1984). These mineralized bodies have lengths of 400–1,540 m, widths of 10–300 m and thicknesses of 15–100 m, with contents of 0.614–1.074% ZrO2, 0.023–0.031% Y2O5 and 0.051–0.065% Nb2O5. The resources of the Sakharjok occurrence have been estimated at 35.8 Mt to 0.16% REO, 0.62% Zr and 0.041% Nb (Batieva and Bel’kov 1984; Pozhilenko et al. 2002; Korsakova et al. 2012).
Lesnoe alkaline intrusion (Russia)
The alkaline intrusion at Lesnoe forms part of the western Keivy alkaline complex, but the reading list for this area is both sparse and written in Russian (Korovkin et al. 2003). The Nb-REE-Zr Lesnoe occurrence is situated in a nepheline syenite, and the main REE-bearing minerals are fergusonite and britholite-(Y). The estimated resources range between 1.511 Mt and 0.22% REO, 1.21% Zr and 0.31% Nb (Korovkin et al. 2003; Korsakova et al. 2012).
1.5.1.1.2. Paleozoic alkaline province (370 Ma)
Khibiny and Lovozero Nb-P-REE alkaline intrusions (Russia)
The Khibiny and Lovozero massifs are the most substantial agpaitic nepheline syenite intrusions in the world.
The Khibiny intrusion (67°74′N; 33°72′E, Russia) covers a surface area of 1,330 km2 and measures nearly 40 km in diameter. It is a massif with concentric intrusions of agpaitic nepheline syenite and alkaline and ultrabasic rocks (Figure 1.12) (Arzamastsev et al. 2008; Kalashnikov et al. 2016). The alkaline rocks of Khibiny have been dated back to 367.5 ± 5.5 Ma using the Rb-Sr method on whole rock (Kramm and Kogarko 1994). Although the size of this intrusion is incomparable, the alteration halo (fenitization) is nonetheless not very broad, not exceeding 50 m. Its main economic interest lies in the exploitation of phosphorus deposits from apatite, spatially associated with urtite and lujavrite. The most substantial deposits are situated along a narrow band to the south of the massif (e.g. Rasvumchorr, Kukisvum-chorr, Yuksporr, Koashva, Niorkpakhk, Oleny Ruchey, Partomchorr). Apatite, the main mineral of the exploited ore, contains 40–41 wt.% P2O5, 1.8–3.5 wt.% SrO, 9,000–11,000 ppm REE and 500–900 ppm Y. The resources measured for the deposits of the Khibiny intrusion are estimated at almost 3,200 Mt to 0.36% REO and 14.87% P2O5 (Eilu et al. 2013; Weihed et al. 2013; Kalashnikov et al. 2016). Many REE minerals have been identified: eudialyte, loparite, fluorapatite, ancylite-(Ce), belovite-(Ce), etc. (Arzamastsev et al. 2008).
The Lovozero intrusion (67°82′N; 34°75′E, Russia) covers a surface of 650 km2 and measures approximately 25 km in diameter (Figure 1.13). The alkaline rocks of Lovozero have been dated back to 370.4 ± 6.7 Ma using the Rb-Sr method on whole rock (Kramm and Kogarko 1994). The massif intrudes garnet-biotite gneisses dating from the Archean. The Lovozero complex is often described as having four stages of intrusion (Eliseev and Fedorov 1953; Gerasimovsky et al. 1966; Kogarko et al. 1995; Kalashnikov et al. 2016):
nepheline syenite with uniform grain, nosean nepheline syenite, metamorphozed nepheline syenite and poikilitic nosean syenite;
embedded lujavrite-foyaite-urtite complex;
layered urtite, lujavrite-eudialyte and foyaite-eudialyte complex;
alkaline lamprophyre dykes (minchiquite, fourchite, tinguaite).
Moreover, the fenitized zone has a width of between 50 and 200 m. Many nepheline syenite and alkaline pegmatite veins intersect the host rocks and extend for more than 100 m around the contact. Surrounding the core of the massif, the lujavrite-foyaite-urtite layered sequence contains layers of loparite.
