Hypothèses associées à l’utilisation des isotopes cosmogéniques terrestres

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The European Raw Material Initiative

Raw materials supply in Europe

EU has many raw material occurrences or deposits but their exploration and ex-traction faces accrued competition, a highly regulated environment and technological limitations regarding the access to mineral deposits (European Commission, 2008). Moreover, the EU is deeply dependant on raw material importation, which can be critical for the high-tech metals due to their economic value and their high supply risks. The production of some materials is concentrated in a small number of coun-tries, e.g. in 2012, 97% of the global supply of Rare Earth Elements (Rare Earth Elements (REE)) was produced by China (Massari and Ruberti, 2013) which also pro-duces 84% of tungsten global supply while 91% of niobium production was ensured by Brazil (US Geological Survey, 2013). Under these conditions the metal supply risk increases, such as the rush for tantalum in 2000 during the boom of mobile phones or, more recently, the significant increase in consumption of REEs (while their supply has suﬀered a severe diminution).
Given that our Earth’s surface and subsurface have not been completely explored and is large enough to contain many hidden deposits, or that some large potential deposits are not currently considered because of technological limitations, it appears that it is not the geological availability but the criticality of mineral raw materials which must be considered as an issue (Rosenau-Tornow et al., 2009). The criticality of a material refers to its uncertainty or risk in supply that could aﬀect the national economy. To address this situation the European Commission launched in November 2008 the “European Raw Material Initiative” with the first objective to identify critical raw materials at the European Union level (European Commission, 2008). The main diﬃculty in defining Critical Raw Material (CRM)s was to develop a methodology to assess criticality and to select raw materials which could be considered as critical using this methodology.

Defining Critical Raw Materials

Material availability

The resources are defined by mining companies, which usually only define the re-serves regarding their short to middle-term needs. Therefore the published reserves cannot be considered as reliable indicators of long-term availability. For some materi-als, mined as by-product, the availability is also conditioned by the major metal of the ore in which they occurred usually in low concentration. This by-product can generate additional revenue but in some cases they are considered to be impurities that can lower the product value or drive up production cost. Another consideration regarding the geological availability is that some metals can occur as accompanying element in some deposits, as the platinum group elements or PGMs (platinum, palladium, os-mium, iridium ruthenium and rhodium) in ultramafic deposits or REE ores which are generally mined and processed for all these metals together. Technological develop-ment can have an important impact on the future availability of certain materials by improving processing, manufacturing or recycling methods.
A more eﬃcient use of resources and recycling thanks to technological advances could increase the existing reserves. That’s why rather than using a static view of geological availability, a more dynamic model was chosen by the European Commis-sion. This model take in consideration not only the general trends in reserves, but also technological developments and changes in the geopolitical-economic framework that impact on supply and demand of raw materials (European Commission, 2010).

Main parameters and definition of criticality

Previous studies all defined criticality on the basis of both supply risk and the associated impact on country’s economy. In 2008, the Committee on Critical Mineral Impacts for the US Economy suggested in an expert report a framework for identifying critical minerals (Committee on Critical Mineral Impacts of the US Economy, 2008). In this report the raw materials are considered critical if there are both important in use and subject to potential supply restrictions. In agreement with this approach, the expert work group of the European Commission has also put forward a relative concept of criticality. They consider that a raw material is “critical” when the risk of supply shortage and their impact on the economy are higher than for most of the other raw material (European Commission, 2010).
This innovative approach uses three main indicators to determine criticality, i.e. the supply risk, the economic importance and the environmental country risk:
• The assessment of the supply risks for a raw material was achieved using widely recognised indexes which evaluate the level of concentration of worldwide pro-duction and are linked to the economic and political stability of the producing countries. The supply risks could also be linked to “company concentration”. For example the high corporate concentration of mine production of niobium and tantalum means that a few companies control the global market, increasing the supply risk for these materials. However, the company concentration was not included in the assessment of supply risks because of the limited information regarding the studied materials (European Commission, 2010),
• The measurement of the economic importance of each candidate raw material was performed by breaking down its main uses and attributing to each of them the value added of the economic sector that has this raw material as input,
• The last indicator relates to the environmental country risk, i.e. the risk that measures might be taken by a country in order to protect its environment and thus endanger the supply of raw materials to the EU. The importance of this indicator is perfectly illustrated by the global supply of REE by China, which has decided in 2010 to drastically decrease its export quotas in order to protect its environment (Massari and Ruberti, 2013).
Based on the methodology described above, a raw material can be considered as critical if it is of high economic importance and faces both high supply and environmental risks.

SCOPE OF THE STUDY

Applying the methodology : list of critical raw materials

First evaluations of the criticality of the 41 material candidates have been made using the previously described method (European Commission, 2010). In 2014, this evaluation has been extended to 54 non-energy, non-agricultural materials (European Commission, 2014). In total this new evaluation defines 20 Critical Raw Materials (CRMs), with more detail provided to the REE by splitting them into ‘heavy’ (HREE) and ‘light’ (LREE) categories and scandium (Figure 1.1). These evaluations are based on their economic importance for the EU economy (represented on the x-axis) and their supply risks (represented on the y-axis) only, since environmental country risks did not add significant changes. The results range from low (pulpwood, diatomite) to very high (vanadium, tungsten) economic importance and from very low to very high (LREE and HREE) supply risks.
Three groups of raw materials have been distinguished by the expert work group (European Commission, 2014), see Figure 1.1. The CRMs are located in the top right corner sub-group, i.e. every material with a supply risk superior to 1 and an economic importance higher than 5 is qualified as critical.
Their high supply risk is mainly due to the high production concentration. Indeed, the share of the worldwide production is dominated by China (antimony, coking coal, fluorspar, gallium, germanium, indium, magnesium, natural graphite, phosphate rock, LREE, HREE, tungsten). For the remaining CRMs the worldwide production is di-vided between Brazil (niobium), Democratic Republic of Congo (cobalt), Kazakhstan (chromium), Russia (PGM), South Africa (chromium, PGM), Turkey (borates) and the United States (beryllium, borates), see Figure 1.2.
Figure 1.2: World map of major CRMs (and Sn) producers with critical metals of interest (LREE, Nb, W) and Sn highlighted in bold (European Commission, 2014; US Geological Survey, 2015).
The two other sub-groups are not considered as critical but it is important to notice that regarding the sub-group on the lower right corner (i.e. low supply risk and high economic importance materials) a small variation in the supply risk may result in a translation upward in the CRMs sub-group.
Although tin does not fall into the criticality zone, its economic importance is largely above the economic importance threshold whereas the associated supply risk is close to the supply risk threshold. As a result, comparatively small changes in tin supply risk can make this material move into the “critical” region. Thus tin can be properly considered as a “near-critical raw material” (Oakdene Hollins and Faunhofer ISI, 2014).

CRMs (LREE, Nb-Ta, W) and Sn consumption

All the CRMs of interest and Sn have a wide variety of uses, which have varied over time mainly in the metallurgical, electronics, automotive and chemical industry. Appendix A.1 lists the principal industrial applications of the CRMs of interest and Sn for each industry in which they are used.

LREE

The demand for rare earth elements has « skyrocketed » in recent years due to their increasing usage in numerous high-technology markets. The global market shares are distributed between high strength permanent magnets (21%), alloying agents in metals (21%), catalysts (19.5%), polishing (13%), glass (7%), phosphors for electronic displays (6.5%), ceramics (6%) and others (Kingsnorth, 2014b). The industrial application of LREE are numerous in economic areas such as aeronautic, automotive (hybrid and electric vehicles), defence, renewable energy technologies (wind turbine, solar panels), medicine (medical imagery) and other economic areas for which they became essential. This wide variety of application for REE came from the configuration of their electrons in the atomic structure, which give them many desirable features: (1) ability of forming alloys with other metals, very strong and light magnetic materials; (2) valuable and distinctive optical properties, including fluorescence and emission of coherent light, essential for laser devices; (3) other unique nuclear, metallurgical, chemical, catalytic, electrical, magnetic, and optical properties (Massari and Ruberti, 2013). However, each REE has its particular uses as the lanthanides are not all interchangeable (Table 1.1). For instance La is the main REE used in nickel metal hybrid (NiMH) rechargeable batteries that powers many electronic products. Along with cerium (Ce), it is used in fluid cracking catalysts in the petroleum industry for the crude oil refining process. Ce is mainly used for autocatalysts and chemical catalysts as cerium carbonate and cerium oxide to increase eﬀectiveness of chemical reactions and reduce the amount of platinum and other precious metal required. Glass and polishing is also a major use of Ce due to its ability to adsorb ultraviolet light. Neodymium (Nd) is mainly used for permanent magnets in neodymium-iron-boron (NIB) magnets for low temperature applications (Curie point at 310°C) and possesses a magnetic energy of up to 2.5 times greater than the former samarium-cobalt magnets (Walters and Lusty, 2011). Accord-ing to Kingsnorth (2014b) demand of Nd (and praseodymium) for rare earth permanent magnets will be the market driver for the foreseeable future.
Tin has been in use since ancient times and its consumption by diﬀerent sectors is varying with time. Since 2000, consumption of tin for electronic soldering application increases in Asian countries, especially China and Japan (Angadi et al., 2015). Tin is primarily used worldwide, in descending order, in solders, tin plates, chemicals, tin alloys (brass, bronze, etc.) and float glass (Figure 1.3). Tin is employed in a wide range of specialised solders of higher or lower melting temperature, and physical properties to support the electronics and industrial sectors. Solders are used in almost every elec-tronic product for conductive joints, and for traditional industrial applications such as joining copper water pipes. Tinplate (i.e. steel with a thin tin coating) is used in pack-aging in the food industry for food and beverages (e.g. tin cans), product containers and various other items (ITRI, 2010). Tin chemicals represent also an important share of tin consumption, primarily used in organic compounds in PVC (doors, windows) to prevent degradation by heat and sunlight. Other uses of tin include non-smelting alloys of tin such as brass, bronze, pewter and even superconductor. Tin as also an essential role in the float glass technology for flat glass manufacturing process (De Cuyper and Delwasse, 1999).

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Nb-Ta

Niobium and tantalum are vital components in a diverse range of products and applications due to their unique properties which include superconductivity, corrosion-resistance, very high melting temperature, shape memory properties, high coeﬃcient of capacitance and bio-compatibility (Shaw and Goodenough, 2011). The majority of nio-bium is consumed in the form of ferro-niobium (FeNb) utilised in the production of high strength low alloy steels (HSLA) used to manufacture vehicle bodies, railway tracks, ship pull, bridges or pipelines. The remaining share is used in manufacturing niobium chemicals, high purity ferro-niobium, niobium alloys and other niobium metal products (Schwela, 2010), see Figure 1.3. The end uses for tantalum are more balanced between capacitor-grade and metallurgical grade tantalum powder, metal products, tantalum chemicals, ingot and carbides (Figure 1.3). Tantalum powders are used in a wide range of applications, primarily for the production of capacitors in mobile phones, due to their ability to hold electric charge.
The unique properties of tungsten are a very high density and melting point, an extreme strength, a high wear resistance, a low coeﬃcient of expansion, a high thermal and electrical conductivity (Pitfield and Brown, 2011). However the global end-uses of tungsten are less diverse comparing to the above-mentioned uses of other CRMs. Tung-sten is primarily used worldwide, in descending order, in hard metal, steel and alloys, mill products and other products (Roskill Consulting Group, 2010), see Figure 1.3. The term hard metals refer to tungsten and cemented carbides used to manufacture very hard materials used for cutting, drilling and wear-resistant coatings in the metal-working, mining and petroleum industry. There is a wide variety of tungsten alloys, the more common being the steel alloys, such as high speed steel, heat resistant steel and tool steel used for metal cutting and other specialised engineering application where hardness and strength are required (Pitfield and Brown, 2011). The term mill products refer to tungsten wire, sheets or rods used in electrical application, electronics, notably in incandescent light bulb filaments, vacuum tubes and heating elements. Other ap-plications include chemical products used as colouring agents in the porcelain industry or in catalysts, phosphors and absorbent gels, as reagents for chemical analysis during medical diagnosis, or as a corrosion inhibitors (Pitfield and Brown, 2011).

The STOICISM project

Project summary

The European Seventh Framework Programme for Research (FP7) launched in mid-2011, oﬀered to support large projects under the umbrella of Nanosciences, Nanotech-nologies, Materials and New Production Technologies (NMP) including “NMP.2012. 4.1-1: New environmentally friendly approaches to mineral processing”. It was rec-ognized through the EU Raw Materials Initiative and Europe 2020 that there was also a need to improve all raw materials eﬃciency to remain as self-suﬃcient and self-sustainable as possible (EU, 2015).
Europe is a major global producer of industrial minerals with around 180 million tonnes per year of products extracted in the EU, with an estimated contribution of e10 billion to European Gross Domestic Product (GDP). In global terms, EU produces 35% of perlite, 20% of calcined kaolin and 20% of diatomite of world demand (EU, 2015). Key markets for these minerals are beverage filtration, coatings, plastic, rubber, cosmetics, insulation and construction materials. Any strategy based on sustainable use of mineral resources has to reduce the impact on the environment through improved eﬃciency and eﬀectiveness of the entire value chain of raw materials.
In this context the STOICISM (Sustainable Technologies for Calcined Industrial Minerals in Europe) project was launched in 2013 with 4-years duration, with the specific objective to enhance the competitiveness of the European industrial minerals industry by developing cleaner, more energy eﬃcient extraction and processing tech-nologies reducing the carbon footprint of several calcined industrial minerals, thereby looking at the whole supply chain from the extraction, beneficiation, waste valorisation and optimisation of the functionality for the end users.
Three industrial minerals, i.e. diatomaceous earth (DE), perlite and kaolin have been selected but results should be directly transferable to many other industrial min-erals.

Project partners and consortium structures

The STOICISM Consortium is led by a major industrial mineral producing com-pany (Imerys minerals Ltd) and consists of 17 partners from 8 diﬀerent European countries. Key contributors on this multidisciplinary platform include several univer-sities, specialized SMEs & corporations, an industry association, as well as applied technology and research institutes. The project is structured in 9 work packages (WP) with associated tasks and with clearly identified milestones and outcomes. The 6 first work packages are complementary and correspond to the main steps of the whole in-dustrial materials supply chain (Figure 1.4).

Table of contents :

I. Introduction
I.1. Early work
I.2. Discoveries from the ocean floor exploration
I.3. The « tectonics, climate and denudation » debate
I.4. This thesis
II. Context
II.1. The Himalaya
II.1.1. Physiographic and geological units
II.1.2. Precipitations and hydrography
II.1.3. Glaciations
II.2. Tectonics viewed by thermochronometry
II.2.1. Tectonic drivers and elevation change
II.2.2. Evolution of tectonics in the Himalaya
II.3. Climate
II.3.1. Greenhouse gases
II.3.2. Heat redistribution, geography and tectonics
II.3.3. Orbital cycles
II.3.4. Global sea-level
II.3.5. Cenozoic climate change
II.4. Denudation
II.4.1. Mechanical and chemical processes
II.4.2. Erosion, transport and deposition
II.4.2.1. Slope processes
II.4.2.2. Fluvial incision
II.4.2.3. Glacial erosion
II.4.2.4. Complementary erosive processes
II.4.3. Sedimentary flux at modern times
II.5. The sedimentary record
II.5.1. The stochastic nature of sediments
II.5.2. The provenance topic
II.5.2.1. Recycling
II.5.2.2. Drainage evolution
II.5.3. Accumulation rates and sedimentary budgets
II.6. Late Cenozoic evolution of the denudation records
II.6.1. Accumulation rates and sedimentary budgets
II.6.1.1. The deep sea basins
II.6.1.2. Turbiditic fans, continental margins and foreland basins
II.6.2. The seawater continental silicate chemical weathering record
II.6.2.1. The seawater 87Sr/86Sr
II.6.2.2. The seawater 10Be/9Be and δ7Li
II.6.2.3. Consequences for the causes of the CO2 fluctuations in the late Cenozoic
II.6.3. The 10Be/9Be detrital record
II.6.4. The detrital thermochronometric record
II.6.4.1. A few words about thermochronometry
II.6.4.2. Detrital thermochronometric data
II.6.5. The in situ thermochronometric record
II.7. Possible causes for an acceleration of denudation rates
II.7.1. Have sea-level fluctuations altered export of sediments to the deep sea?
II.7.2. Active tectonics
II.7.3. A shift to dry and stormy climate?
II.7.4. A shift to variable climate?
II.7.5. Enhanced glacial erosion?
II.8. Tables
III. Aim of the thesis
III.1. Synthesis of the topic
III.1.1. Tectonics
III.1.2. Climate
III.1.3. Chemical denudation
III.1.4. Physical denudation
III.1.4.1. Sediment accumulation rates
III.1.4.2. Detrital thermochronometry
III.1.4.3. Detrital cosmogenic nuclides
III.1.4.4. In situ thermochronometry
III.2. Aim of the thesis
III.2.1. A record of erosion at an orogenic scale
III.2.2. A new erosion record for South Asia
III.2.3. A check on erosion patterns and increased variability at low latitudes
III.3. Developed approach
III.3.1. Sedimentary archives
III.3.1.1. Bengal Fan Exp. 353 – 354
III.3.1.2. Siwalik sections in the Valmiki Wildlife Sanctuary, Bihar, India
III.3.2. Methodology
IV. Methodologic overview
IV.1. The cosmic flux and its quantification
IV.1.1. The neutron cosmic flux
IV.1.2. The muon cosmic flux
IV.1.3. Quantification of the cosmic flux
IV.2. Computation of denudation rates
IV.2.1. Determination of production rates
IV.2.2. Scaling models
IV.2.3. Analytical computation of quartz in situ 10Be denudation rates
IV.2.4. Topographic and glacial shielding
IV.3. Limits of the 10Be method
IV.3.1. Analytic measurements
IV.3.2. Reproducibility 1
IV.3.3. 10Be production rates, geography of the catchment, provenance and recycling
IV.3.4. Steady-state landscape
IV.3.5. Impact of stochastic events
IV.3.6. Exposure during transport to sink or recent exposure
IV.3.7. Dating
V. Data report: calcareous nannofossils and lithologic constraints on the age model of IODP Site U1450
V.1. Abstract
V.2. Introduction
V.3. Material and methods
V.3.1. Calcareous Nannofossils
V.3.2. Age model
V.4. Results
V.4.1. Calcareous Nannofossils identifications
V.4.2. Age Model
V.5. Tables
VI. Steady erosion of the Himalaya during the late Cenozoic climate change
VI.1. Introduction
VI.2. Approach for erosion rate quantification
VI.3. 10Be concentrations
VI.4. Apparent erosion rates
VI.5. Sr-Nd isotopes
VI.6. Test of the climate forcing hypothesis
VI.7. Implications
VI.8. Methods
VI.9. Extended Methods
VI.9.1. Material
VI.9.2. 10Be/9Be preparation and measurements
VI.9.3. 10Be paleoconcentrations
VI.9.4. Production rates and erosion rates
VI.9.5. Sr-Nd isotopic measurements on bulk silicate samples
VI.9.6. Computation of the fraction fG
VI.9.7. Modern geochemical and granulometric budgets in the Ganga
VI.9.8. Test of the climate forcing hypothesis
VI.9.9. Temporal variability of cosmogenic nuclide production rates
VI.10. Tables
VII. The Valmiki Sections: a new sedimentary record of the Central Himalaya (Draft)
VII.1. Introduction
VII.1.1. The South Asian Monsoon during the late Cenozoic
VII.1.2. Approach
VII.2. Context
VII.2.1. Geology, physiography and precipitation distribution
VII.2.2. The Siwalik molasses
VII.2.3. The Narayani-Gandak drainage basin
VII.3. Material and methods
VII.3.1. Description of the Valmiki Sections
VII.3.2. Material
VII.3.3. Magnetostratigraphy and stochastic correlation dating
VII.3.4. Major and trace element measurements
VII.3.5. Stable isotope measurements
VII.4. Results
VII.4.1. Description of the Valmiki Sections
VII.4.2. The frontal Churia (CR) fold
VII.4.3. The Valmiki Nagar (VR) fold
VII.4.4. Paleomagnetic dating
VII.4.5. Sedimentology
VII.4.6. Age estimate of the frontal Churia (CR) fold
VII.4.7. Age estimate of the Valmiki Nagar (VR) fold
VII.4.8. Major and trace elements
VII.4.9. C and O isotopes
VII.5. Discussion
VII.5.1. Fluvial style evolution
VII.5.2. Recycling
VII.5.3. Detection of a shift of provenance?
VII.5.4. Evolution of precipitations
VII.5.5. Late Miocene shift to C4-dominated vegetation
VII.5.6. Late Pliocene shift back to mixed vegetation
VII.6. Conclusion
VII.7. Tables
VIII. Late Cenozoic evolution of erosion rates in the Narayani-Gandak basin, Central Himalaya (Draft)
VIII.1. Introduction
VIII.1.1. Has climate forced erosion rates in the late Cenozoic?
VIII.1.2. Approach
VIII.2. Geological context of the Central Himalaya
VIII.2.1. Structure and lithology
VIII.2.2. Long-term structural evolution
VIII.2.3. The Narayani-Gandak drainage basin
VIII.2.4. The Valmiki Sections
VIII.3. Material and methods
VIII.3.1. Material
VIII.3.2. Sr-Nd isotopic composition measurements
VIII.3.3. Lithological fraction computing
VIII.3.4. 10Be/9Be measurements
VIII.3.5. 10Be concentration determination
VIII.3.6. 36Cl measurements and 10Be recent exposure contribution
VIII.3.7. 10Be floodplain exposure contribution
VIII.3.8. Determination of paleoerosion rates
VIII.4. Results
VIII.4.1. Sr-Nd isotopes and lithologic fractions
VIII.4.2. 36Cl measurements and recent exposure contribution
VIII.4.3. 10Be paleoconcentrations
VIII.4.4. Evolution of the drainage basin
VIII.4.5. Erosion rates
VIII.5. Discussion
VIII.5.1. Biased 10Be concentrations for old samples?
VIII.5.2. Variability of apparent erosion rates
VIII.5.3. Comparison with other 10Be datasets
VIII.5.4. Comparison with detrital thermochronometry
VIII.5.5. Comparison with in situ thermochronometry
VIII.5.6. Possible causes of the difference between 10Be and in situ thermochronometry
VIII.6. Implications
VIII.6.1. The late Cenozoic climate change in Central Himalaya
VIII.6.2. The late Cenozoic climate change and erosion rates
VIII.7. Conclusion
VIII.8. Tables
IX. Synthesis
IX.1. Context
IX.1.1. Climate change and erosion rate estimates
IX.1.2. Assumptions associated to the use of terretrial cosmogenic nuclides
IX.2. Results
IX.2.1. The Bengal Fan record
IX.2.2. The Valmiki Section record
IX.3. Conclusion
X. Synthèse
X.1. Contexte
X.1.1. Changement climate et estimation des taux d’érosion
X.1.2. Hypothèses associées à l’utilisation des isotopes cosmogéniques terrestres
X.2. Résultats
X.2.1. L’enregistrement du cône du Bengale
X.2.2. L’enregistrement des sections Valmiki
X.3. Conclusion
Bibliography