Metallic Resources 2 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 2 presents various studies in notable metallogenic regions or deposits worldwide 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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Seitenzahl: 561
Veröffentlichungsjahr: 2023
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Table of Contents
Cover
Table of Contents
Title Page
Copyright Page
1 Lithium Mineralization, Contributions of Paleoclimates and Orogens
1.1. Properties and distribution of lithium in minerals and Earth reservoirs
1.2. Lithium metallogeny and gitology
1.3. Acknowledgments
1.4. References
2 Metallogeny of the Abitibi Greenstone Belt, Canada
2.1. Introduction
2.2. Mining history
2.3. Geological context
2.4. Mineral resources and metallogeny
2.5. An evolving industry: technical and scientific challenges, and innovations in the mineral resources world
2.6. An exceptional metallogenic context: a brief discussion
2.7. Conclusion
2.8. Acknowledgments
2.9. References
3 The Unconformity-related Uranium Mineral System of the Athabasca Basin (Canada)
3.1. Introduction
3.2. Defining the critical elements of the unconformity-related uranium mineral system of the Athabasca Basin
3.3. Implication of the mineral system concept applied to the exploration of unconformity-related uranium deposits
3.4. Conclusion
3.5. References
4 North African Mississippi Valley-Type Deposit and Its Link with the Alpine Chain Evolution
4.1. Introduction
4.2. Geological settings of MVT deposits of the Atlasic system: main ore deposits and districts
4.3. Discussion
4.4. Supergene non-sulfide Pb-Zn mineralization associated with MVT deposits
4.5. Acknowledgments
4.6. References
5 West African Leo-Man Shield Metallogenic Province
5.1. Introduction
5.2. Geology of LMS
5.3. Spatiotemporal distribution of gold in LMS
5.4. Spatiotemporal distribution of other LMS metallogenic systems
5.5. Conclusion
5.6. References
Appendix 1: Lithium Mineralization, Contributions of Paleoclimates and Orogens
Appendix 2: Metallogeny of the Abitibi Greenstone Belt, Canada
A2.1. Location of the Superior Province and of the Abitibi greenstone belt
A2.2. Gold deposits of the Abitibi greenstone belt
A2.3. VMS deposits of the Abitibi greenstone belt
A2.4. Ni-Cu-PGE, Fe-Ti-V, talc, magnesite and chrysotile deposits
A2.5. Fe, Cu-Mo, Mo-Bi, aluminosilicates, rare metals and Li deposits
List of Authors
Index
Summary of Volume 1
End User License Agreement
List of Tables
Chapter 1
Table 1.1. Average lithium content in various Earth reservoirs, types of rocks...
Table 1.2. Behavior of glass and very common minerals under chemical alteratio...
Table 1.3. Mineral-magma partition coefficients (Kd) for several elements, tra...
Table 1.4. TOT clays, illite, chlorite-smectite mixed-layer and lithium-bearin...
List of Illustrations
Chapter 1
Figure 1.1. Configuration of the two lithium isotopes
Figure 1.2. Isotopic lithium composition in various Earth reservoirs. Modified...
Figure 1.3. Number of occurrences for the most widespread lithium minerals (Gr...
Figure 1.4. Maximal theoretical concentration of lithium (expressed as Li2O we...
Figure 1.5. Compared lithium and water content (approximated by loss on igniti...
Figure 1.6. Histogram of lithium content (in ppm) of a collection of 213 sampl...
Figure 1.7. Logarithmic scale graph of the evolution of Li content of residual...
Figure 1.8. Logarithmic scale graph of the evolution of the content of liquids...
Figure 1.9. Theoretical evolution of lithium concentration (in ppm or mg/L) of...
Figure 1.10. Block models of mature and immature salars showing the distributi...
Figure 1.11. Variations of lithium concentration in brines in the salt-bearing...
Figure 1.12. Geological map and section of Clayton Valley (Nevada, USA)
Figure 1.13. Geological map of McDermitt caldera (at the Nevada-Oregon limit, ...
Figure 1.14. Geological map and section of the Miocene deposit of Sonora (Mexi...
Figure 1.15. Geological map and section of Miocene basin of Jadar (Serbia)
Figure 1.16. Cross sections of various lithium deposits
Figure 1.17. Anatectic model for the generation of pegmatites (barren and Li-r...
Figure 1.18. Example of lithium pegmatites at the border of a field of sterile...
Figure 1.19. Schematic vertical section of a lithium mineralized pegmatite-apl...
Figure 1.20. Simplified geological map and section of the Almendra-La Fregened...
Figure 1.21. Photos of lithium-bearing pegmatites of the La Fregeneda-Almendra...
Figure 1.22. Two examples of rare-metal granites in dyke, and in pipe map view...
Figure 1.23. Examples of magmatic and hydrothermal facies associated with rare...
Figure 1.24. Metal content tonnage depending on the ore content for lithium-be...
Figure 1.25. Geochemic cycle of lithium and lithium mineralization. Modified f...
Chapter 2
Figure 2.1. Geological map of the Superior Province in Canada, taken from Perc...
Figure 2.2. Geological map of the Abitibi greenstone belt. Taken from Dubé and...
Figure 2.3. Spatial distribution of the three main types of rocks of the Abiti...
Figure 2.4. Relative surface area for the seven volcanic assemblages (a), for ...
Figure 2.5. Schematic representation of key elements of the geology and metall...
Figure 2.6. Several examples of sedimentary rocks
Figure 2.7. Simplified summary of the different auriferous mineralization styl...
Figure 2.8. Geological map of the Abitibi greenstone belt showing the distribu...
Figure 2.9. Ore deposits of over 100,000 ounces (3.1 Mt) of gold of the Abitib...
Figure 2.10. Metamorphosed sulfide-bearing mineralization and alteration assem...
Figure 2.11. Examples of pre-Timiskaming deposits
Figure 2.12. Examples of auriferous orogenic quartz and carbonate veins
Figure 2.13. Examples of VMS-type Cu-Zn deposits and key features
Figure 2.14. Geological map of the Abitibi greenstone belt showing the distrib...
Figure 2.15. Distribution of VMS deposits associated with the Abitibi volcanic...
Figure 2.16. Data on the number of VMS deposits and total tonnage per district...
Figure 2.17. Geological map of the Abitibi greenstone belt showing the distrib...
Figure 2.18. Schematic diagrams showing the distribution of Ni-Cu-(PGE), Cr, a...
Figure 2.19. Examples of Ni-Cu-PGE, Fe-V and Cr mineralization
Figure 2.20. Examples of porphyry-style mineralization, aluminosilicate-bearin...
Figure 2.21. Aerial views of the former Manitou mine site
Chapter 3
Figure 3.1. Geological map of the Canadian Shield (a: modified from Pehrsson e...
Figure 3.2. The mineral system concept (McCuaig and Hronsky 2014) applied to t...
Figure 3.3. Interpretative structural map of the magnetic linear gradients and...
Figure 3.4. Interpretative structural map of the magnetic linear gradients and...
Figure 3.5. Interpretative cross sections through the Wollaston Mudjatik trans...
Figure 3.6. Representative snapshots of the main deformation styles and releva...
Figure 3.7. Reference model with the lithosphere at a higher horizontal shorte...
Figure 3.8. Evolution of the conceptual models for the fluid flow at the origi...
Figure 3.9. Lithostructural classification diagram with end member summary cha...
Figure 3.10. Calculated offset of the unconformity along the first- and second...
Figure 3.11. Macro- and microstructures across a reactivated Trans-Hudson faul...
Figure 3.12. Macro- and microstructures across a reactivated Trans-Hudson faul...
Figure 3.13. Geological sections across the Cigar Lake deposit. (a) Original c...
Figure 3.14. Compilation of isotopic ages associated with U mineralization in ...
Figure 3.15. Schematic diagram illustrating an idealized hydrodynamic model (L...
Chapter 4
Figure 4.1. Geologic map of northwest Africa showing the main structural domai...
Figure 4.2. Present-day interpretative N–S cross-section along the Tunisian sa...
Figure 4.3. Structural setting of Touissit-Bou Beker Mississippi Valley-Type o...
Figure 4.4. (a) Geological map of the northeastern part of “a chaîne-des-Horst...
Figure 4.5. Longitudinal ENE–WSW cross-section through the “Touissit shelf” sh...
Figure 4.6. Longitudinal NW–SE cross-section through the Upper Moulouya distri...
Figure 4.7. Geological map of the Upper Moulouya district showing regional geo...
Figure 4.8. Detailed geological map of Jbel Bou Dahar reef-bearing complex sho...
Figure 4.9. Longitudinal N–S cross-section through the Liassic reef-bearing ca...
Figure 4.10. Geologic map of Bou Beker-El Abed deposits (Morocco–Algeria borde...
Figure 4.11. Geological setting of the northeastern termination of the Algeria...
Figure 4.12. Geological map of the Mesloula district showing the main geologic...
Figure 4.13. Geologic and metallogenic map of Northern Tunisia showing the mai...
Figure 4.14. Longitudinal E–W cross-section through the Bou Grine deposit show...
Figure 4.15. Longitudinal N–S cross-section through the Fedj-El-Adoum deposit ...
Figure 4.16. (a) Simplified geological map of the Bou Jaber district showing t...
Figure 4.17. Geological map of the Slata Pb-Ba-(± Zn) district and its southwe...
Figure 4.18. Distribution of δ18OV-SMOW and δ13CPDB values for the main genera...
Figure 4.19. Lead isotopic compositions of sulfide separate fractions along wi...
Chapter 5
Figure 5.1. Key elements of a mineral system: example of Precambrian orogenic ...
Figure 5.2. Simplified geological map at 1:10 million scale of Archean and Pal...
Figure 5.3. Reconstruction of the Columbia supercontinent at ca. 1.8 Ga. Modif...
Figure 5.4. Lihospheric-scale cross-sections along the northern and eastern ma...
Figure 5.5. Gold metallogenic map of the Paleoproterozoic Baoulé-Mossi domain....
Figure 5.6. Time and space evolving litho-structural maps highlighting the pol...
Figure 5.7. Metallogenic map that highlights the distribution of the main mine...
Appendix 2
Figure A2.1. Map of the northern part of North America showing the Canadian pr...
Guide
Cover Page
Table of Contents
Title Page
Copyright Page
Begin Reading
Appendix 1 Lithium Mineralization, Contributions of Paleoclimates and Orogens
Appendix 2 Metallogeny of the Abitibi Greenstone Belt, Canada
List of Authors
Index
Index
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 2
Geodynamic Framework and Remarkable Examples in the World
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 4EUUKwww.iste.co.uk
John Wiley & Sons, Inc.111 River StreetHoboken, NJ 07030USAwww.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 978-1-78945-136-8
ERC code:PE10 Earth System Science PE10_10 Mineralogy, petrology, igneous petrology, metamorphic petrology
1Lithium Mineralization, Contributions of Paleoclimates and Orogens
Éric GLOAGUEN1,2, Jérémie MELLETON1, Blandine GOURCEROL1 and Romain MILLOT1
1 BRGM, Orléans, France
2 ISTO, CNRS, University of Orléans, France
1.1. Properties and distribution of lithium in minerals and Earth reservoirs
1.1.1. Physicochemical properties of lithium
Lithium is the third element in the periodic table, containing three protons, hence Z = 3, which defines its place in Mendeleev’s periodic table of elements. It is a very light alkaline metal element with a density of 0.53, which is half the density of pure water. The average ionic radius of lithium is 0.76 Å. It is very similar to the ionic radius of magnesium (0.72 Å), which explains the frequent substitution of magnesium by lithium in minerals. When in pure state, it is a silvery metal, soft and breakable, with a melting point of only 180.5°C. Metallic lithium oxidizes under air and forms lithium oxide Li2O. Given its very high reactivity, particularly with water and air, it does not exist in native state. Its boiling point at 1,342°C is high. It is the element with the highest specific heat capacity, 3,582 J/(kg·K). Lithium has three electrons, two on the first electron shell and a single electron on the second electron shell (Figure 1.1). The first electron shell reduces the attraction exerted by the protons in the nucleus on the electron of the second shell, which explains the low electronegativity of lithium, 0.98 on the Pauling scale, one of the lowest among all elements. It can thus very easily lose its electron to the benefit of a more electronegative element and form Li+ cation. Lithium exists in the form of two natural and stable isotopes, 92.5% in the form of 7Li and only 7.5 % in the form of 6Li (Figure 1.1.). Lithium 7 (7Li) is one of the rare nuclides that was formed during the Big Bang, while a very small amount of 6Li was generated during this event. The large difference in relative mass (∼16 %) between 6Li and 7Li may generate significant isotopic fractionation. The isotopic composition of lithium in a sample is denoted in relative deviation (per thousand, denoted by ‰) with respect to the value of a reference standard, which is lithium carbonate L-SVEC (7Li/6Li = 12.02 ± 0.03‰) (Flesch et al. 1973), whose value of δ7Li is 0‰ by definition:
Isotopic fractionation in the Earth’s systems is very important, with a variation in δ7Li of over 60‰ (Tomascak 2004).
Figure 1.1.Configuration of the two lithium isotopes
At the first approximation, the more negative values of δ7Li are measured in mantle rocks, with the majority of rocks having an average signature between 0 and 5‰, with the exception of carbonates (above +15‰). Waters have, on average, much higher signatures with larger variations than those measured for rocks. Finally, the present seawater has a value around +31‰.
Figure 1.2.Isotopic lithium composition in various Earth reservoirs. Modified after Tang et al. (2007)
1.1.2. Uses of lithium
Lithium is used in various forms: minerals, metals, carbonates, hydroxides, various chemical compounds. In 2018, 50,750 tons of lithium (metal equivalent) was used in the world (Lefebvre and Tavignot 2020). These various forms are related to various purity degrees required for the uses. The field of ceramics does not generally require very pure lithium, which allows its direct use from natural minerals. On the other hand, the field of batteries and chemistry require very high purity lithium (≥99.5% Li), which involves complex treatment processes applied to specific minerals or brines. A very high level of purity is in fact required in order to reach the performances, longevity and also safety of batteries or chemical components. In 2018, the main uses of lithium were as follows (Lefebvre and Tavignot 2020): cathodes and electrolytes of batteries (58%), glass and ceramics (37%), lithium greases (11%), air treatment and air conditioning (5%), mold fluxes for steel production by continuous casting (5%), the production of pharmaceutical products and polymers (2%), aluminum metallurgy (2%) or other minority uses, including cement manufacturing, pyrotechnics or water treatment. Worldwide uses of lithium are driven by the field of batteries, whose lithium consumption has multiplied seven times in 10 years, from 4,260 tons in 2008 to 29,435 tons in 2018. This very high increase in lithium consumption for the field of batteries is expected to continue, leading to an annual consumption between 150,000 and 300,000 tons in 2030. This explains the large number of mineral exploration projects for lithium, conducted on all continents, for several years.
The various uses of lithium are presented in detail in Labbé and Daw (2012) and Christmann et al. (2015), with the following main uses being drawn and summarized from them. In lithium-ion batteries, lithium is used for the cathode, in the form of mixed oxide of lithium and another metal, such as cobalt, manganese, nickel or phosphorus. Hence, there are six main types of cathodes: (1) LCO (lithium cobalt oxide, LiCoO2); (2) LMO (lithium manganese oxide spinel, LiMn2O4) ; (3) LNO (LiNiO2); (4) NCA (Li(Ni,Co,Al)O2); (5) LFP (LiFePO4) and (6) NMC (Li(Ni,Mn,Co)O). For the electrolyte, lithium is used in the form of lithium hexafluorophosphate (LiPF6), and also in the form of other various complex lithium salts (LiBF4, LiAsF6, LiI, LiClO4, LiCF3SO3, LiN (CF3SO2)2, LiN(C2F5SO2)2, LiB(C2O4)2, etc.) in organic solvents or solid polymers. The anode is generally made from carbon (graphite), but sometimes from lithium titanate Li4Ti5O12. In lithium-metal-polymer batteries, the anode is made from lithium metal. In the industry of glass and ceramics, lithium is used as an additive for manufacturing certain types of glass and ceramics, including vitro-ceramics. Due to the addition of lithium and titanium, the glass expansion is practically zero, because of the negative expansion coefficient of spodumene microcrystals that compensate for the expansion of the glass matrix. For the floor tiling industry, lithium lowers the melting temperature. Depending on the processes, lithium is used in the form of minerals, oxide or carbonate. Generally speaking, the presence of lithium makes it possible to lower the melting temperature of products (energy savings), decrease viscosity, reduce the amount of bubbles, reduce the thermal expansion coefficient and improve chemical resistance. In the industry of lubricating greases, for example for ball bearings, lithium is used in the form of metallic soap, resulting from the reaction of a fatty acid with lithium hydroxide. These greases contribute to maintaining good lubricating properties over a wide temperature range and good resistance to water and oxidation, while being compatible with other additives. The air treatment and purification sector uses about 1,000 tons of lithium per year. Lithium is used in the form of lithium bromide as refrigerant fluid for absorption climatization. Lithium is also used in dehumidification processes, particularly in the form of lithium chloride that can absorb nearly 10 times its weight in water. Finally, lithium aids air purification by eliminating CO2 in enclosed spaces using lithium hydroxide or peroxide. Continuous casting of steel uses about 1,000 tons/year metallic Li equivalent in the form of spodumene, petalite or lithium carbonate. Lithium improves fluidity and accelerates casting. This process can be used to manufacture parts that are much larger than the mold, for example the iron tracks of railroads, as the solidified part is extracted simultaneously with molten metal casting in the mold. In the pharmaceutical industry, lithium is mainly used in the form of carbonate, for the treatment of bipolar disorder, in addition to the treatment of depression and other various neuropsychiatric disorders, and also for dermatological creams (lithium succinate). Lithium is widely used in aluminum metallurgy for the production of aluminum-lithium alloys for the aerospace industry. Indeed, the addition of lithium decreases the density of the alloy and increases its elasticity. Many alloys on the market have lithium contents ranging from 1.1 to 3.8%. These alloys are used in particular for parts of the structures of Airbus, Boeing and Bombardier aircraft, and also for fighter aircraft. NASA shuttles also use these alloys.
1.1.3. Lithium minerals
A minimum of 120 lithium-bearing mineral species are identified in the database of the International Mineralogical Association (IMA, see: https://mineralogy-ima.org/). This number is a minimum, as many mineral species containing low amounts of lithium are not recorded. These 120 species include 73% of silicates, 19% of phosphates and 8% of oxides, hydroxides, arsenates, chlorides or fluorides (Grew et al. 2019; Grew 2020). Among these, 12 species are the most common (Figure 1.3), with over 50 worldwide known occurrences (Grew 2020). Conversely, jadarite LiNaSiB3O7(OH), a mineral from the family of zeolites, has only been known and identified in the mineralization of Jadar in Serbia (Stanley et al. 2007), but may represent a significant European deposit in the following years.
A ranking of these various minerals in descending order of their lithium oxide content (Figure 1.3) shows that the groups with the highest lithium content are phosphates, inosilicates and nesosilicates, followed by phyllosilicates. Lithium mineralization therefore depends on the lithium mineral species present in the rock and on their relative proportions in it. Finally, it can be noted that spodumene is the most abundant among lithium-rich minerals (8% weight, Figure 1.4), which partly explains the fact that lithium extraction processes for this mineral are several decades old.
Figure 1.3.Number of occurrences for the most widespread lithium minerals (Grew 2020)
1.1.4. Distribution of lithium in Earth’s reservoirs
Compared to other alkaline metals, such as sodium and potassium, which are among the major components of the upper continental crust, lithium is far less abundant, with an average concentration of only 0.002%, or 20 ppm, equivalent to 20 g of lithium per ton of rock (Taylor and McLennan 1985).
The average concentration of lithium in the upper continental crust is about 35 ± 11 ppm (2σ) (Teng et al. 2004), three times higher than in the ocean crust and basalts (Table 1.1). The concentration of granites is on average 30 ppm, but this average covers a very wide variability. Peraluminous granites are generally far richer in lithium.
Figure 1.4.Maximal theoretical concentration of lithium (expressed as Li2O weight percentage) in lithium minerals that are most common or important in terms of mineralization
COMMENT ON FIGURE 1.4.– Source of data: International Mineralogical Association (https://mineralogy-ima.org). Lepidolite (not in the figure) is not a mineral species, but the name of a series representing the solid solution of polylithionite-trilithionite, whose general formula is K(Li,Al)3(Si,Al)4O10(F,OH)2.
As an example, the Variscan prealuminous granites of Cornwall have an average content between 108 and 445 ppm (Simons et al. 2017), which varies according to the generations and excluding the rare-metal granites. Clay-rich marine sediments are relatively rich, with an average from 60 to 80 ppm, but once more this average covers a wide disparity. At the first approximation, the lithium content of aluminous detrital sediments seems, on average, to be above the average of the upper continental crust, as well as the crust types of granites resulting from the melting of sediments.
Table 1.1.Average lithium content in various Earth reservoirs, types of rocks, sediments and soils
(source: (a) Li (2000); (b) Teng et al. (2004); (c) Taylor and McLennan (2008); (d) Ling et al. (2018))
Lithology units
Lithium content (ppm)
Mantle
1,5
b
Ocean crust (MORB)
9
a
, 10
b
Lower continental crust
13
b
Upper continental crust
20
a
; 35–11
b
Granites
30
a
Micaschist
34
a
Hemipelagic muds
79
a
; 57
c
Deep-sea carbonates
5
c
Clays
45
a
; 42–77
b
Marine clays
66
a
; 28–109
b
River clays
30
a
Loess
35
a
; 29–16
b
Soils
33
a
Secondary (transported) bauxites
47–613
d
1.2. Lithium metallogeny and gitology
1.2.1. Lithium behavior in geological processes
1.2.1.1. Lithium behavior in surface processes
At the Earth’s surface, several processes have an effect on the mobilization or immobilization of lithium, particularly processes of alteration, erosion and evaporation in the presence of variable amounts of water. Lithium has a strong affinity for the water in which it can be found as tetrahedral complex [Li(H2O)4]+ because of its small ionic radius (Rudolph et al. 1995). By comparison, alkaline metals with larger ionic radius, such as rubidium and cesium, form octahedral complexes with water (Mähler and Persson 2012). In chemical alteration processes, rocks altered at the surface (alterites) may have their lithium content increase or decrease with respect to the content of the initial rock, irrespective of its lithium concentration. Indeed, lithium is shared between the neo-formed clay minerals and the surface waters related to alteration (Millot et al. 2010). In low-temperature aquifers, waters allow the formation of a relatively significant proportion of clays (Pogge von Strandmann et al. 2016) that trap lithium, integrating it in the structure of clays and/or adsorbing it at their surface. Lithium may also be trapped by chlorites as a substitute for magnesium. Therefore, there is a relative proportion of lithium integrated in the structure of minerals that cannot be mobilized by waters unless the minerals are altered. Conversely, the proportion of interlayered lithium (between clay layers) can be mobilized via water circulation. Lithium retention in the structure of secondary clay minerals occurs because its ionic radius is well adapted to the octahedral cavity of the latter (Huh et al. 2004). Hence, during supergene alteration, lithium released by primary minerals is integrated proportionally with aluminum in neo-formed clays (Horstman 1957; Hirst 1962) and surface waters contain a small amount of dissolved lithium. This phenomenon is quite prominent in clay-rich geological formations, in which lithium concentration is correlated with aluminum oxide concentration (Teng et al. 2004) and also with the chemical alteration index (molar ratio of Al2O3/[Al2O3 + CaO + Na2O + K2O]) of Nesbitt and Young (1982). Supergene alteration processes therefore tend to concentrate lithium in alterites and in certain bauxites, even though there is not enough data to determine the averages. These processes can be observed through isotopic measurements of lithium. Indeed, surface waters (rivers, lakes, Figure 1.2) have a δ7Li > 4‰, which means that these waters are enriched in 7Li compared to alterites and rocks. This enrichment illustrates the fact that the light 6Li isotope is preferentially integrated in the site with the highest coordination degree (Oi et al. 1991), which corresponds to octahedral sites in secondary minerals (clays, chlorites). Minerals are thus enriched in 6Li, while waters are enriched in 7Li at the same time. The relative enrichment of continental waters in 7Li largely explains the strongly enriched signature of δ7Li = +31‰ of seawater.
The dissolved salts composition of surface or near-surface waters depends mainly on the initial nature of the latter (rainwaters, etc.), on the nature of the rocks with which they interact and on the water residence time, which is the time of interaction between waters and rocks (e.g. Elango and Kannan 2007). Water gets loaded with lithium, provided that it interacts with a rock that contains it and can release it. This capacity depends on mineral phases that constitute the rock and on their stability in the presence of a given composition of water (Table 1.2).
Volcanic rocks contain variable proportions of glass, which correspond to fractions of magma that are not crystallized due to rapid cooling. This glass can be altered very rapidly, for example from 2,000 to 30,000 years in the case of ashes, into an assembly of aluminosilicates, allophane and imogolite (Hiradate and Wada 2005). The alteration of volcanic rocks by surface waters leads to an enrichment of the latter in potassium, lithium, magnesium, boron and, to a lesser extent, sodium and calcium (Warren 2010). The concentration of waters mineralized in interior (or semi-closed) basins and the enrichment in salts by evaporation transforms these waters into brines when the total concentration of dissolved salts exceeds 3.5%, with the concentration corresponding to that of seawater.
Table 1.2.Behavior of glass and very common minerals under chemical alteration. Modified from Elango and Kannan (2007)
Phases
Formulas
Relative resistances
Chemical alteration processes
Halite
NaCl
Very low
Dissolving
Gypsum
CaSO
4
.2H
2
O
Very low
Dissolving
Pyrite
FeS
2
Low
Dissolving and oxidation
Calcite
CaCO
3
Low
Dissolving
Dolomite
CaMg(CO
3
)
2
Low
Dissolving
Glass
Composition variable
Low
Hydrolysis
Olivine
(Fe,Mg)
2
SiO
4
Moderately low
Oxidation, hydrolysis
Pyroxene
(Ca,Na,Mg,Li)(Mg,Fe,Ti,Al)(Si,Al)
2
O
6
Moderate
Oxidation, hydrolysis
Plagioclases
NaAlSi
3
O
8
-CaAl
2
Si
2
O
8
Moderate
Hydrolysis
Amphiboles
(Ca,Mg,Fe,Al,Na)
7
Si
8
O
22
(OH)
2
Moderate
Oxidation, hydrolysis
Biotite
K(Mg,Fe)
3
[AlSi
3
O
10
](OH,F)
2
Moderate
Oxidation, hydrolysis
Potassium feldspar
(K,Na)AlSi
3
O
8
Moderately high
Hydrolysis
Muscovite
KAl
2
AlSi
3
O
10
(OH)
2
High
Hydrolysis
Quartz
SiO
2
Very high
Very slow dissolving
Clays
K
x+y
[(Si
4-x
Al
x
)O
10
(Al
2-y
Mg
y
)(OH)
2
]
Very high
Hydrolysis
1.2.1.2. Behavior of lithium during metamorphism
As already noted, due to a similar ionic radius between Li+ (76 pm) and Mg2+ (72 pm), lithium, with 6 coordinance in phyllosilicates (Wenger and Armbruster 1991), substitutes for magnesium in octahedral sites, as well as in interlayer positions to balance electric charges in clays. At the Earth’s surface, lithium is mainly carried by clays, particularly produced by supergene alteration. Lithium concentration in metapelites is thus higher when they result from continental domains with strong supergene alteration (Qiu 2011). From diagenesis to greenschist facies, lithium remains with magnesium successively in smectites, illites then chlorites during the increase in temperature. The latter has a negligible effect on the lithium concentration of metapelites at the approach of greenschist facies (∼300°C).
Conversely, metamorphic dehydration from greenschist facies to granulite facies may lead to a significant, though not systematic, loss of lithium. Indeed, one of the key factors of lithium preservation in metapelites during metamorphism is the stability of hydrated magnesium phyllosilicates such as chlorite, biotite and staurolite. In particular, staurolite is by far the most lithium-rich mineral compared to other minerals in metapelites (Dutrow et al. 1986; Feenstra et al. 2003). Hence, following the pressure-temperature path and the mineralogical transformations, lithium is increasingly mobilized by the fluid (Chan et al. 1994; Chan and Kastner 2000; Chan et al. 2002) above the temperature of smectite-illite transformation.
If mineralogical carriers of lithium are destroyed, the amount of lithium lost by meta-sediment in contact with the fluid depends on the temperature at which the fluid loss occurs (Chan and Kastner 2000; Millot and Négrel 2007; Vigier et al. 2008; Scholz et al. 2009, 2010), but also on the nature of neo-formed minerals and their capacity to integrate lithium in their structure.
Consequently, a sedimentary formation may lose between 20 and 50% of its initial lithium content during metamorphic dehydration reactions between 250 and 650°C (Zack et al. 2003; Marschall et al. 2007; Teng et al. 2007; Qiu et al. 2011) and even beyond that temperature. Certain examples suggest that the passage from amphibolite facies to granulite facies may lead to a loss of 90% of the initial lithium content in metapelites (Qiu 2011). As an example, the whole-rock geochemistry analysis of the schists of Bündnerschiefer formation (marine metasediments of Western Alps) at various metamorphic grades by Garofalo (2012) shows, in this case, that the most significant loss of lithium occurs at the middle of facies of amphibolites, therefore above 500°C. This loss of lithium is associated with strong dehydration of rocks (Figure 1.5) and interpreted as being related to metamorphism, with only mobile elements in fluids (Li, B, Si) undergoing losses (Garofalo 2012). As a hypothesis, this loss may be related to the destruction of staurolite, chlorite and muscovite according to the following reaction (Spear et al. 1999): staurolite + chlorite + muscovite ⇨ andalusite + biotite + vapor.
Figure 1.5.Compared lithium and water content (approximated by loss on ignition) of schists and micaschists of marine origin of Bündnerschiefer formation (Western Alps) at various metamorphic grades (Garofalo 2012)
1.2.1.3. Behavior of lithium in magmatic processes
During the crystallization of magmas of granitic composition, the crystallization of anhydrous minerals such as potassium feldspar (∼40% vol.), quartz (∼30% vol.) and plagioclases (∼20% vol.) has the overall effect of increasing the relative concentration of residual magma in incompatible elements in aluminosilicates (H2O, Li, P, LILE, HFSE, etc.) (Černý et al. 2005). A key to understanding this phenomenon is the mineral-magma partition coefficient (Kd), which reflects the preference of a given chemical element, denoted by i, to integrate the structure of a mineral or to remain in the residual liquid due to its incompatibility with the structure of the mineral. During a crystallization at equilibrium, this preference will be reflected by a difference between the concentration (denoted by C) of element i in the mineral and the concentration of the same element i in the magma where the mineral crystallizes. The ratio of concentrations of element i in the mineral and in the magma corresponds to this partition coefficient Kd:
Despite this simple definition, the mineral-magma partition coefficients for many elements still remain poorly constrained (Table 1.3), as many parameters such as the initial content of the considered chemical element [C0]i in the initial magma, or still, the oxygen fugacity of magma, must influence the value of Kd, which may explain the significant variations between the published studies (Table 1.3).
Table 1.3.Mineral-magma partition coefficients (Kd) for several elements, traces in granitic magmas. Modified from Villaros and Pichavant (2019) and included references
Biotite
Muscovite
Plagioclase
Orthose
Quartz
Min
Preferred
Max
Min
Preferred
Max
F
1.56
2.25
4.00
0.94
1.00
1.92
0.01
0.01
0.01
Li
0.41
0.55
1.67
0.12
0.19
0.82
0.10
0.05
0.01
Rb
1.11
1.90
2.13
0.96
1.60
1.75
0.06
0.83
0.01
Ba
5.63
14.40
15.67
3.41
4.50
8.14
0.19
6.70
0.01
Cs
0.27
0.30
0.57
0.16
0.20
0.36
0.44
0.13
0.01
Magma crystallizes in the form of several minerals: potassium feldspar, plagioclase feldspar, biotite, muscovite and quartz. The overall partition coefficient of the rock, denoted by D, corresponds to the modal fraction of each mineral, multiplied by the Kd and can be calculated as follows:
where:
In the case of lithium, the partition coefficient D of a peraluminous1 granite composed of 33% quartz, 27% potassium feldspar, 25% plagioclase, 9.5% muscovite and 5.5% biotite is therefore defined by:
According to the values of Kd employed (minimum, preferred or maximum, see Table 1.3), Kd of lithium varies significantly between 0.07 and 0.23. However, as Kd is below 1, residual magmatic liquids must get enriched in lithium (and also in Rb, Cs, etc.) during granite crystallization. In order to estimate the enrichment in lithium of a residual peraluminous magma related to the crystallization of peraluminous granite, various approaches are used. The first approach involves the use of Rayleigh’s fractionation equation in the case of crystallization at equilibrium to model the enrichment in trace elements (Shearer et al. 1992):
where F is the fraction of residual magmatic liquid.
Figure 1.6.Histogram of lithium content (in ppm) of a collection of 213 samples of granites of various origins according to whole-rock geochemistry analysis: 5 ppm class size
(source: BRGM, the French Geological Survey)
It is not easy to estimate the initial lithium content of granitic magmas. However, the initial lithium content of magma (C0) is clearly one of the critical parameters. The higher it is, the richer the residual magma. Data available on granites generally indicate quite low values, 30 ppm Li on average for the granites (Table 1.1). It is higher for peraluminous crustal granites, of about 79 ppm Li, according to the data in Figure 1.6.
BRGM data on 213 whole-rock analyses performed on samples of granites of various origins range between 2.4 and 316 ppm. About 50% of these granites have a Li content ≤60 ppm and only 25% of them have a Li content >120 ppm. If the initial lithium content of the magma (C0) is 120 ppm, therefore relatively high, this leads, in the case of an ideal crystallization at equilibrium, to a lithium concentration of the last percent of residual magmatic liquid between 4,100 and 8,466 ppm Li, depending on the Kd used.
This Rayleigh’s fractionation model is however not realistic, as it assumes that 100% of the residual liquid is extracted between the crystals, which is not in agreement with the significant viscosities of these magmas (Clemens and Petford 1999) and the impossibility to separate crystals from liquids (Bea 2010).
The Langmuir model (1989) uses a more realistic configuration with the presence of a zone of solidification, mixture of crystals and magmas between the crystallized granite and the uncrystallized magma. In this model, the concentration of a trace element in the residual liquid is defined as follows:
where:
f: fraction of fractionated liquid resulting from crystallization in the zone of solidification that returns to the non-fractionated magma in the magma chamber;
F: total fraction of residual magma liquid.
If magma crystallizes very rapidly, then f is close to 0; if magma crystallizes very slowly, f tends to 1, and the residual magma has the time to escape from the zone of solidification, return and get mixed in the unfractionated magma.
This type of model seems to be applicable to magma chambers established deeply in the lower crust or for deep-seated plutons, but it is difficult to apply to plutons resulting from crustal melting, issued and established in the mid- to upper continental crust.
Figure 1.7.Logarithmic scale graph of the evolution of Li content of residual liquid during the crystallization of a magma of granitic composition between f = 1 (liquid) and f = 0.01, composition of the last percent of residual liquid
COMMENT ON FIGURE 1.7.– The highest theoretical lithium concentrations (8,466 ppm) are obtained with Rayleigh fractionation in the ideal (unrealistic) case of crystallization at equilibrium, and the lowest (maximum 1,167 ppm) in the case of the Langmuir in situ crystallization model (1989), calculated for a fraction of fractionated liquid resulting from the crystallization in the zone of solidification that returns to the unfractionated magma in the magma chamber equal to 0.3 (f = 0.3) fixed up to 10 % of residual liquid, then linearly decreasing between 0.3 and 0.08 for a total fraction of residual magma liquid from 0.1 to 0.01 (F = 0.1 to F = 0.01), from a magma of identical initial lithium concentration of 120 ppm. It is also important to note the importance of different Kd resulting from Table 1.3.
Based on the previous elements, it can be noted that, as the models get increasingly complex (and become more realistic), the enrichment of residual magma in incompatible elements becomes less significant (Figure 1.7). Moreover, the processes through which crustal granite intrusions are built are by themselves critical for the possibility to generate magmas rich in incompatible elements. Indeed, enrichments in incompatible elements by fractionated or in situ crystallization are possible in the case of magma chambers undergoing crystallization. However, the works of the last decade are increasingly calling into question the formation of crustal granite intrusions by the crystallization of magma chambers to the benefit of a construction by successive pulses of limited volumes of anatectic magmas within the same zone (Clemens et al. 2010; Clemens and Stevens 2016). The consequences of this mode of building crustal granite intrusions are dramatic for potential enrichments: the low volume of magma and its probable rapid crystallization very strongly limit the possible enrichments by fractionated or in situ crystallization, and must lead to a concentration in lithium and incompatible elements of residual liquids at the same order of magnitude as the initial liquids issued from partial melting. While crustal granites are probably capable of producing residual liquids at the origin of pegmatites-aplites, these are probably easily enriched in incompatible elements compared to the parent granite.
It is now important to examine the compositions in incompatible elements that can be generated by partial melting of metasediments (see Černý et al. (2005) and the references therein).
The enrichment in incompatible elements of the anatectic liquid during partial melting can be modeled by batch melting (Shaw 1970). In this model, the chemical equilibrium between restite and magma is maintained until the final extraction of magma, according to the equation:
This equation shows that the richer the melting metasediment is in micas, the lower the enrichment of the first liquid drops resulting from partial melting in incompatile elements. These elements have the tendency to partially remain in the micas, actually limiting the enrichment of the produced liquid.
Hence, for two metasediments with quartz-biotite-plagioclase-sillimanite-garnet-muscovite containing 120 ppm of lithium each, the first one containing 43% biotite and the second one 23% biotite, the first percentage of liquid produced will have a lithium concentration of 556 ppm and 777 ppm, respectively.
Figure 1.8 shows the essential role of initial concentration (C0) in obtaining liquids very rich in incompatible elements. In order to obtain, with a metasediment composed of 43% biotite, 1–5% anatectic liquids with lithium contents of the order of magnitude of whole rock contents of economic pegmatites, or of the order of 9,000–10,000 ppm, these meta-sediments should contain a minima about 1,800 to 2,500 ppm lithium before starting to melt.
Figure 1.8.Logarithmic scale graph of the evolution of the content of liquids formed by batch melting of two metasediments composed of 43% biotitte, 25% plagioclase, 15% sillimaniite, 11% quartz, 3% muscovite and 3% garnet
COMMENT ON FIGURE 1.8.– The first meta-sediment has a total content of 120 ppm and the second of 2,500 ppm. For each sample, there are three curves, depending on the value of Kd used for the micas that lead to a variation of the global partition coefficient D of the rock. It can be seen here that in order to obtain magmas with lithium contents of the order of magnitude of economic pegmatites, a si ignificant pre-enrichment is required, in the absence of which this composition cannot be obtained by partial melting.
1.2.1.4. Behavior of lithium in hydrothermal processes
1.2.1.4.1. Magmatic fluids
At the end of crystallization of rare-metal granites, high-temperature hydrothermal fluids, mainly rich in silica, phosphorus, lithium and fluorine are sometimes produced (Roda-Robles et al. 2016). When these fluids are trapped, they form veins or lodes with lithium quartz-phosphates. These are generally phosphates of the amblygonite-montebrasite series whose general formula is (Li1-xNax)Al(PO4)(OH,F). These veins are mainly observed inside or in the proximity of rare-metal granites (Roda-Robles et al. 2016). The best known example of a quartz-amblygonite lode system is represented by the rare-metal granite of Argemela and by the quartz-amblygonite mine of Argemela in Portugal (Michaud et al. 2020). These hydrothermal fluids can also be diffused in formations hosting rare-metal granites and form significant diffusion halos. These halos can be evidenced by geochemistry campaigns on river sediments or soil. The research conducted by Aubert (1969) on the rare-metal granite of Beauvoir (France) is a good illustration.
1.2.1.4.2. Geothermal fluids
In hydrothermal systems, the partitioning of lithium between fluids and rocks interacting with fluids depends on many parameters. The main parameters are the temperature of fluid-rock interaction, the typology of fluids (salt content, pH, etc.), the lithium content of host rocks, the mineralogical carriers structural position of lithium (exchangeable versus non-exchangeable), the granulometry and the porosity-permeability (Romer et al. 2014). Among all these parameters, the fluid-rock interaction temperature is one of the most important and this importance is illustrated, on the one hand, with the global increase in lithium concentration in various types of fluids with temperature (Figure 1.9) (Fouillac and Michard 1981), and, on the other hand, with the existence of geothermometers based on the Na/Li ratio (see Sanjuan et al. (2014) and the references therein) according to an equation of the type:
with 855 < x < 2 002 and –1.275 < y < 1.322, for values of x and y varying depending on geological contexts of geothermal environments (sedimentary, volcanic, basement, etc., see Figure 1.9).
As already noted in section 1.2.1.1, during the alteration of lithium-bearing rocks by the fluids, there is a competition between the dissolution of primary minerals and the formation of secondary minerals (Pogge von Strandmann et al. 2020). If the primary minerals are dissolved, and there is no formation of secondary minerals, mainly clays, the lithium content of fluids will be significant and the isotopic signature of lithium will preserve the signature of the primary rock. Conversely, if there is a formation of secondary minerals, these will capture a part of lithium and induce a modification of the isotopic signature in lithium of the fluid (equilibrium fractionation). The lithium content of fluids will therefore depend on the lithium concentration of primary rocks (and of the mineralogical carriers of lithium), on the nature of the fluids present and on their temperature. Lithium can be integrated in smectites, smectite-chlorites mixed-layers, illites and chlorites (see Millot et al. (2010) and the references therein). Between 200 and 300°C, lithium is partitioned between the fluid and the newly formed clay minerals (Pogge von Strandmann et al. 2016). In experiments on the crystallization of lithium-bearing smectites, either dioctahedral smectites (Li-montmorillonites) or trioctahedral smectites (hectorites), the amount of lithium integrated in the smectites increases between 25 and 250°C (Calvet and Prost 1971; Vigier et al. 2008).
As an example, laboratory experiments show that the lithium concentration of hectorites increases from 120 to 3,400 ppm between 25 and 250°C (Vigier et al. 2008). Conversely, in high-temperature geothermal systems, above 300°C, the formation of clay minerals is inhibited and lithium is partitioned in the geothermal fluid (Pogge von Strandmann et al. 2016), which therefore has its lithium content increased.
Figure 1.9.Theoretical evolution of lithium concentration (in ppm or mg/L) of fluids in various geological environments with temperature increase
COMMENT ON FIGURE 1.9.– Strong lithium concentration requires strong sodium concentration, which is here arbitrarily fixed at 10 g/L, which is geologically impossible for fluids in all these environments. This concentration is arbitrarily fixed in order to show that geothermal fluids of basements require a much highertemperature than geothermal brines of sedimentary basins in order to reach the same lithium concentration. Sodium concentration also evolves with temperature, and it is the Na/Li ratio that is the geothermometer and not the lithium concentration in itself. The equations employed are: Fouillac and Michard (1981) for aqueous or salted geothermal fluids; Michard (1990) for geothermal fluids in granites; Kharaka et al. (1982) and Kharaka and Mariner (1989) for the brines of sedimentary basins.
1.2.2. Lithium gitology and metallogeny: geological settings and types of mineralization
1.2.2.1. Overall view
Lithium mineralization can be grouped in two families. A first family covers sedimentary-hydrothermal mineralization formed at the surface or relatively near the surface. The genesis conditions are strongly controlled by climate, topography and geological setting. A second family covers magmatic to hydrothermal mineralization, whose genesis and location spread from middle crust to the surface. There are frequently more or less significant relations between these two families, with the genesis of magmatic-hydrothermal mineralization having a direct contribution to the stock of lithium of sedimentary-hydrothermal mineralization directly via magmatic fluids or indirectly via volcanic products or rocks.
1.2.2.2. Sedimentary-hydrothermal mineralization
Sedimentary-hydrothermal mineralization with lithium takes several distinct forms: brines, clays, zeolites (jadarite) and bauxites. Only the first three types can actually constitute deposits. The main environments (or paleo-environments) in which these sedimentary-hydrothermal mineralization occur are mainly intra-mountain or continental basins, rifts and calderas with acid magmatism. The climate associated with sedimentation is mostly dry, or with a closed hydrological system, which seems to be a prerequisite for avoiding the dilution of the lithium contained in surface waters. Stratiform sedimentary-hydrothermal mineralization and lithium bauxites are thus testifying for environments or paleo-environments that have a large number of common characteristics. Indeed, the formation of stratiform mineralization with lithium requires the trapping of a flow of lithium in a fixed place for a certain period of time in order to have an accumulation. The source and the trap may be very close to one another or coincident in the case of clays. The trap may also take the form of a physical depression that may be a closed (endoreic), semi-closed or open continental sedimentary basin, a graben, a rift or still a volcanic caldera. The trap may be a bauxite formation itself. The flow of lithium is provided by the surface water and underground waters that come from drainage where there are volcanic rocks and/or basement regionally surrounding the trap. A part of the lithium flow can also be provided by a volcano-sedimentary detrital fraction deposited in the sedimentary sequence or by hydrothermal and/or in situ supergene alteration of volcano-sediments that are generally of rhyolitic composition. Magmatic brines can also contribute to the lithium stock (Benson et al. 2017; Castor and Henry 2020). The entrapment of lithium-bearing waters occurs in a variable manner by the competition between the evaporation rate and the opening degree of the basin (or of the trap). The most significant lithium mineralization is then encountered under dry climate in an interior basin surrounded by rocks whose lithium is significantly leachable.
1.2.2.2.1. Lithium-bearing brines
According to Bowell et al. (2020), lithium brines are generally defined as hypersaline, with a salinity ranging between 1.7 and 24 times that of seawater, that is, 35 g of dissolved salt per liter. Lithium brines tend to be characterized by concentrations of dissolved ions near saturation for many salts, particularly halite in mature salars. Brines are composed of several ions, including sodium, chlorine, potassium, boron, sulfate and lithium. Nevertheless, lithium enrichment of continental brines is not systematic, highlighting the fact that lithium may come from certain appropriate geological sources (volcanic glass, favorable basement rocks, etc.). Lithium-bearing brines are mainly encountered in three types of environments: in evaporite basins (salar type) mainly in South America and Tibet, in certain geothermal fields and certain oilfields. In these various environments, lithium brines are pumped to the surface then stored in basins where salts can be concentrated by evaporation. Processes have also been elaborated to directly extract lithium from the brine and thus avoid the long evaporation phase.
Lithium brines of evaporite basins are located in recent continental basins containing lacustrine evaporites generated by high evaporation rates with respect to precipitations (Kesler et al. 2012). At the surface of these basins, there are frequently salt crusts, including surface lakes known as salars, whose sedimentary filling is essentially constituted of evaporites. Brines are located in various aquifers inside these porous salt-bearing formations. These brines are encountered in various types of ecological environments defined by two poles, mature salars with chemical dominant and immature salars with detrital dominant (Houston et al. 2011) (Figure 1.10). Depending on climate and on the detrital contribution, the filling of the sedimentary trap varies from mainly lacustrine fluviatile detrital sequences (clays, sand, etc.) to rare evaporites to salars with an important evaporite nucleus. There is a continuum of possibilities between these two poles. The circulations of fluids with a remobilization of lithium are significant in these basins. Moreover, the circulations of fluids are often amplified by significant thermal gradients related to proximal volcanism. Stratiform lithium mineralization is mainly represented by evaporites containing Li, clays containing Li, and brines circulating in the basin. Mature salars are observed in drier regions (e.g. West Puna, Argentine), while immature salars are located in more humid regions and/or in more humid climate periods (NE Puna) (Houston et al. 2011; Bowell et al. 2020). Mature salars are dominated by a massive halite nucleus, with alternations and lenses of detrital sediments (silt/clay, sand). The halite nucleus consists of a thin layer of upper porous halite and a thick lower sequence of massive halite (Figure 1.10).
In-depth porous spaces are completely filled by diagenetic cementation, leading to thick sequences (>60–70 m) of massive halite (Warren 2010). Immature salars are dominated by detrital sediments such as clay, silt and sand with several intercalated evaporites (halite and gypsum). In these salars, brines do not generally attain saturation in halite because of more humid conditions. Brine volumes are generally high due to the high porosity of detrital sedimentary layers and several brine aquifers may be encountered in-depth. The lithium content of brines present in aquifers of salars are not at all homogeneous and vary strongly from one zone to another, illustrating the control of lithologies situated around and under the salar (Figure 1.11). This is also consistent with the existence of salar that does not contain lithium-bearing brines.
Clayton Valley (Nevada, United States) is an example of mineralization in the form of lithium-bearing brines hosted by a basin with clastic dominance where lithium-bearing clays are also located (Figure 1.12). Until now, only the brines are exploited. Nevertheless, several exploration companies are evaluating the potential of clays as a lithium resource. Clayton Valley is located in the Basin and Range province of the Western United States, which is characterized by a dry climate. This zone corresponds to a semi-closed basin, lined by high mountains comprising a complex metamorphic nucleus and a system of normal faults (Davis et al. 1986) (Figure 1.12). The sediments deposited in the basin are mainly silts, sands and gravels intercalated with clays in the form of illite, smectite and kaolinite (see Munk et al. (2016) and the references therein). The basin is also filled with tuffs and silicic rhyolites from Miocene to Pliocene, and tuffaceous lacustrine facies containing a significant amount of lithium, 215 to 490 ppm Li2O on average (see Munk et al. (2016) and the references therein). The alternation of dry and humid periods during Pleistocene accounts for the formation of layers of clay, evaporites and associated brines.
Figure 1.10.Block models of mature and immature salars showing the distribution of facies and of the main hydrological components. Simplified from Houston et al. (2011)
COMMENT ON FIGURE 1.10.– In the mature model, the extension and recession of marginal facies resulting from tectonics and from the climate variation lead to thepossibility to transfer diluted waters into the salar nucleus, which is extremely developed. In the immature model, the transmission of diluted waters into the nucleus, much more limited, is also possible.
Figure 1.11.Variations of lithium concentration in brines in the salt-bearing nucleus of the Salar de Atacama (Chile)
COMMENT ON FIGURE 1.11.– This map suggests a privileged lithium contribution of surface and underground waters from drainages south of the Atacama Salar. Outside the rich zones, the salt-bearing nucleus surrounded by a black line containsbrines whose lithium concentration ranges between 900 and 1,000 ppm. Gruber and Medina (2010) data on the numerical model of shaded terrain Shuttle Radar Topography Mission 90 m of NASA.
The variations in the quantity of inputs of detrital sediments with respect to evaporite deposits, combined with the play of faults, have allowed the formation of at least six aquifers containing brines (Figure 1.12). A combination of hydrothermal activity and leaching of volcanic ashes and clays throughout time is probably at the origin of the presence of lithium in the aquifers of Clayton Valley (Munk et al. 2016). Lithium brines are located within 6 aquifer units of various natures (layers of volcanic ashes, halite layers, tuff layers, travertine layers and gravel layers).
Figure 1.12.Geological map and section of Clayton Valley (Nevada, USA)
COMMENT ON FIGURE 1.12.– Simplified geology according to the 1:500,000 geological map of Nevada of the Nevada Bureau of Mines and Geology, encased in the numerical model of shaded terrain Shuttle Radar Topography Mission 30 m of NASA. According to the shaded DTM, the Clayton Valley is practically a closed basin. Section from Davis et al. (1986). Lithium-bearing brines are present in six aquifers, and lithium-bearing clays under exploration are also present. The values in ppm indicate the lithium concentrations of the circulating fluids. Values from Davis et al. (1986).
Other geological environments are also sometimes favorable to the presence of lithium brines. This is the case for certain geothermal fields and certain oilfields. For most of the geothermal fluids in contact with volcanic rocks or granites in the in-depth reservoir, rock leaching and hydrothermal alteration (precipitation of illite or smectite) are probably the main processes controlling the lithium concentration in brines. Na/Li ratios depend not only on temperature, but also on other parameters such as the salinity and origin of fluids, or the nature of reservoir rocks in contact with geothermal fluids (Sanjuan et al. 2014). European examples include the geothermal field of Cesano (Italy, Li = 350 mg/L, volcano-sedimentary), the geothermal field of the Upper Rhine Valley (France and Germany, Li = 220 mg/L, Triassic evaporites and Variscan granite) and the geothermal field of the South Crofty mine (South-West England, Li = 125 mg/L, Variscan granite).
1.2.2.2.2. Lithium-bearing clays
Lithium-bearing clays correspond to several species of clays in which lithium is, either integrated in the mineral structure, or exchangeable in interlayer position or adsorbed in the form of ions at the surface of clay. Depending on lithologies and alteration conditions, various types of minerals can be formed (Table 1.4): trioctahedral smectites (e.g. hectorite), dioctahedral smectites (e.g. swinefordite), chlorite-smectite mixed-layer (e.g. lithium-tosudite), chlorites (e.g. cookeite) or dioctahedral deficient micas (illite). Trioctahedral smectites neo-formed during the dry periods in lagoon-lacustrine environments are frequently rich in lithium, but with highly variable concentrations ranging between 400 and 6,000 ppm Li (Tardy et al. 1972). The main known deposits are located in the Basin and Range province (Western United States), and include the deposits of McDermitt caldera, Fish Lake Valley, Hector, Mexico (Sonora) and Peru (Falchani-Macusani). Other locations are also known in the Miocene basins in Serbia, Turkey, Morocco, but there are probably in many other locations worldwide. In these deposits, the source of lithium is frequently a rhyolitic volcanism (Benson et al. 2017) whose volcanic products (tuffs, glass, etc.) located in a depression (caldera, graben, lake, etc.) were altered by hydrothermal fluids contemporary with the neighboring volcanic activity, as volcanic glasses are easily alterable (Table 1.2
