Search

Long-term management of the mineral resource supply incorporating anthropogenic environmental impacts is crucial for sustaining human society. This is especially true for recovery of by-products and critical raw materials (CRM) whose production is often unable to respond quickly to rapid changes in consumption trends. As part of European H2020 research and innovation, the ION4RAW project aims at obtaining reliable estimates of by-products and CRM, and at developing ionometallurgy processes to improve their extraction from primary resources. Targeted metals are by-products (Te, Se, Re and Mo) and CRM (Bi, Ge, In, Co, Pt, Sb) in 5 selected Cu-Ag-Au ore deposits through the world (Cononish Gold mine, Scotland; Cobre Las Cruces and El Valle Boinas, Spain; El Porvenir and Cerro Lindo, Peru). The final objective of this study is to determine the carrier minerals of CRM and by-products, the variability of their chemistry, their distribution and quantification, in order to improve their recovery during ore treatment processes. We currently inventory by-products and CRM by characterizing ores and gangue, using a multi-technical approach (bulk chemistry and X-Ray diffraction, optical and scanning electron microscopic observations, µX-ray fluorescence mapping, EPMA spot analyses and laser ablation-ICP-MS). We present here the preliminary results of El Porvenir and El Valle Boinas that are two calcic skarn-related deposits defined by their garnet composition. El Porvenir (Peru), owned by Nexa Resources, is a Pb-Zn ore deposit associated with andradite–bearing skarn, exploited in an underground mine located in the Western Cordillera of the Andes mountain range in central Peru.El Valle-Boinas (Spain), owned by Orvana Minerals Corp, is a Cu-Au ore deposit associated with a grossular-bearing skarn, exploited in an underground mine located in Cantabrian Mountains, 60 km southwest from Aviles in Spain.Mineralogical investigations indicate that the major ore consists of chalcopyrite, galena, sphalerite, pyrite with minor pyrrhotite, tennantite-tetrahedrite–series minerals and tellurides. The electron microprobe allows analyzing micron-sized metal-carrier minerals, including electrum, Bi-Pb sulfosalts, hessite [Ag2Te], stannoidite, determining the composition of tennantite-tetrahedrite-series minerals (argentotennantite containing up to 12 wt% Ag and 5 wt% Bi) and detecting traces in major ore at a detection limits of 200-1000 ppm (for example, galena significantly contains Ag, Sb and Te). The laser ablation-ICP-MS was tested at maximum power of the laser and at different beam diameters adapted to the grain sizes (from 85 to 10 µm). Laser ablation-ICP-MS analyses with a beam diameter of 10 µm confirms EPMA data and allows detecting lower metal contents, such as Se, Rh, Pd, In, Te, in main ore minerals at detection limits of the ppm.

International audience; Water in calcium silicate hydrate (C-S-H) is one of the key parameters driving the macroscopic behavior of cement materials for which water vapor partial pressure has an impact on Young's modulus and the volumic properties. Several samples of C-S-H with a bulk Ca/Si ratio ranging between 0.6 and 1.6 were characterized to study their dehydration/hydration behavior under water-controlled conditions using 29 Si NMR, water adsorption volumetry, X-ray diffraction, and Fourier-transform near-infrared diffuse reflectance under various water pressures. Coherent with several previous studies, it was observed that an increase in the Ca/Si ratio is due to the progressive omission of Si bridging tetrahedra, with the resulting charge being compensated for by interlayer Ca, and that water conditioning influences the layer-to-layer distance and the achieved NMR spectral resolution. Water desorption experiments exhibit one step toward low relative pressure, accompanied by a decrease in the layer-to-layer distance. When sufficient energy is provided to the system (T ≥ 40°C under vacuum) to remove the interlayer water, the shrinkage/swelling is partially reversible in our experimental conditions. A change in layer-to-layer distance of less than 3 Å is measured in the C-S-H between the wet and dried states. When the bridging SiO 2 tetrahedra are omitted, interlayer Ca interacts with layer O and water interacts with the cations and potentially with the surfaces. This structural organization is interpreted as a mid-plane monolayer of water in the interlayer space, this latter accounting for about 30% of the volume of C-S-H particles.

The mechanisms of selenate (SeO42–) sorption by Friedel’s salt (AFm-Cl2), a layered double hydroxide phase found in (altered) cement-based materials, were studied using a combination of wet chemist...

International audience

Aristilde L.; Lanson B.; Charlet L. (2013) Langmuir, 29,; International audience; Many emerging pollutants from pharmaceuticals, pesticides or products for domestic or industrial use are found in the environment and pose the problem of achieving good chemical or ecological status of this system. In the environment, these pollutants can interact with different phases that make up soils or sediments, such as organic matter, natural oxyhydroxides, or clay minerals. However, to date there is very little data describing the reaction mechanisms and the nature of the bonds involved in these interactions (Aristilde et al., 2013). In this context, and in order to improve the state of knowledge on the behaviour of emerging pollutants in the environment, we propose to study the adsorption of two organic molecules, sulfamethoxazole (SMX) and metoprolol tartrate (MPT), considered as emerging pollutants onto a Ca-montmorillonite. SMX and MPT are an antibiotic and a cardioselective beta blocker, respectively, and are widely found in soils and aquatic ecosystems, with concentrations up to several micrograms per liter. In this study, SMX and MPT have been in contact with Ca-montmorillonite for 24 hours at pH 6. Different concentrations, varying from0.1 mg/L to 1 mg/L, were studied. The resulting solids were characterized by X-ray powder diffractometry at constant temperature (25°C) and different humidities (from 10 to 90%). Initial results showed differences in the position (interlayer distance) of the 001 reflection of montmorillonite. In the presence of organic molecules and at low humidity, the interlayer distance is greater than that observed in the case of Ca-montmorillonite. This result indicates that the interlayer space has been modified, in particular by the insertion of organic molecules. For relative humidities above 50%, there are no more differences between the samples with and without organic molecules. Due to their small size, organic molecules do not induce significant swelling when the interlayer space contains many water molecules. To complete this study, analyses of the atomic pair distribution function (PDF), were carried out on the starting materials (Ca-montmorillonite, SMX and MPT) as well as on the montmorillonite after having been in contact with the organic molecules. The comparison between the PDFs confirms the adsorption of organic molecules since characteristic peaks of C-H bonds belonging to the CH 3 groups of SMX and MPT are visible on the montmorillonite PDFs after contact with the organic molecules. However, the interatomic distances between C and H seem to be slightly modified indicating a potential reaction mechanism involving these groups. Aristilde L.; Lanson B.; Charlet L. (2013) Langmuir, 29, 4492-4501.

International audience; On-line, real-time chemical and mineralogical analyses on drill cores are highly demanded by mining companies. However, they are a challenge because of drill core surface state and sample heterogeneities. We selected four rock samples: highly porous, siliceous breccia and serpentinized harzburgite coming from the base of a nickel laterite profile in New Caledonia which were sonic drilled, and fine grained, homogeneous sandstone and coarse grained granite which were diamond drilled and provided by Eijkelkamp Sonic Drill with unknown origin. The samples were analysed at five surface states (diamond or sonic drilled, cut as squares, polished at 6 and 0.25 μm, powdered

International audience

Tracking metal pollution in surface water is a major environmental, public-health and economic issue. Knowledge of the behaviour of metals such as zinc (Zn), in stream sediments and water, is a key factor to improving river water quality. Because the isotopic compositions of Zn can be used as an environmental tracer for tracking the sources of man-made materials and its transport into water and soil, we have used Zn isotopes for studying the anthropogenic impact on a watershed. As a case study, we chose a small watershed in the Loire River basin, near Orleans (France). The Egoutier spring issues in a pristine area, but its water is affected a few kilometres downstream by liquid effluents from a wastewater treatment plant (WWTP) and farther down still by diffuse pollution from road traffic. We sampled the liquid effluents as well as water and sediments along an upstream to downstream transect. For liquid samples, we took “grab” samples and integrated samples using passive DGT (Diffusive Gradients in Thin films) samplers. The advantages of DGT are (1) to pre-concentrate in-situ the Zn dissolved in water—avoiding a time-consuming chemical preparation—and (2) to integrate the potential variations of Zn isotopic signature over time. The mobile fraction of sediments—that released by the leaching in 0.2N HCl—was also investigated. The δ66/64Zn values in water and sediments along the upstream/downstream profile clearly showed the anthropogenic input of WWTP effluents in the river, which was still visible several kilometres downstream in water. This dissolved anthropogenic contribution is easily transported along the transect and only slightly fixed by adsorption on sediments, probably due to their low clay-mineral content. For the farthest downstream sample, affected by road traffic, the pollution source is difficult to discern due to the similar δ66/64Zn values in WWTP effluents and in road-traffic particles. Here, the use of DGT has proved to be a major asset: during a rainfall event, road traffic particles were leached by rainwater, forming runoff with a relatively high Zn content that flowed into the river, and DGT monitoring showed it to be an adequate method for discerning discontinuous anthropogenic input into the river water.

International audience; The objective of the SOLSA project (EU-H2020) is to develop an analytical expert system for on-line-on-mine-real-time mineralogical and geochemical analyses on sonic drill cores. As one aspect of the system, this paper presents the building of the hyperspectral library and its incorporation into sparse unmixing techniques for mineral identification. Twenty seven spectra representing 14 minerals have been collected for the library. Three sparse unmixing techniques have been investigated and evaluated using simulated data generated from our hyperspectral library, and real hyperspectral data acquired from a serpentinized harzburgite sample. Among the three techniques, the collaborative sparse unmixing by variable splitting and augmented Lagrangian (CLSUnSAL) method provided the best accurate results on the simulated data. In addition, the results of the CLSUnSAL method show high correlation with that of the QEMSCAN® analysis on the harzburgite hyperspectral data.

International audience; The SOLSA project aims to develop an innovative on-line-on-mine-real-time expert system, combining sonic drilling, mineralogical and chemical characterization and data treatment. Ideally, this combination, highly demanded by mining and metallurgical companies, will speed up exploration, mining and processing. In order to evaluate the instrumental parameters for the SOLSA expert system, portable and laboratory analyses have been performed on four samples with contrasting lithologies: siliceous breccia, serpentinized harzburgite, sandstone and granite. More precisely, we evaluated the influence of the surface state of the sample on the signals obtained by portable X-Ray Fluorescence (pXRF) for chemistry and portable Infra-Red spectroscopy (pIR) for mineralogy. In addition, laboratory Raman spectroscopy, X-Ray Diffraction (XRD), XRF and ICP-OES laboratory analyses were performed to compare surface bulk mineralogical and chemical analyses. This presentation highlights (1) the importance of coupling chemical and mineralogical analytical technologies to obtain most complete information on samples, (2) the effect of the sample surface state on the XRF and IR signals from portable instruments. The last point is crucial for combined instrumental on-line sensor design and the calibration of the different instruments, especially in the case of pXRF.

International audience; The prediction of the long term trace element mobility in anthropogenic soils would be a way to anticipate land management and should help in reusing slightly contaminated materials. In the present study, iron (Fe) and zinc (Zn) status evolution was investigated in a 100-year old Technosol. The site of investigation is an old brownfield located in the Nord-Pas-de-Calais region (France) which has not been reshaped since the beginning of the last century. The whole soil profile was sampled as a function of depth, and trace elements mobility at each depth was determined by batch leaching test. A specific focus on Fe and Zn status was carried out by bulk analyses, such as selective dissolution, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Fe and Zn status in the profile samples was also studied using laterally resolved techniques such as μ-particle induced X-ray emission (μ-PIXE) and μ-Rutherford backscattering spectroscopy (μ-RBS). The results indicate that (i) Fe is mainly under Fe(III) form, except a minor contribution of Fe(II) in the deeper samples, (ii) some Fe species inherited from the past have been weathered and secondary minerals are constituted of metal-bearing sulphates and Fe (hydr)oxides, (iii) ferrihydrite is formed during pedogenesis (iv) 20 to 30% more Fe (hydr)oxides are present in the surface than in depth and (v) Zn has tetrahedral coordination and is sorbed to phases of increasing crystallinity when depth increases. Zn-bearing phases identified in the present study are: complex Fe, Mn, Zn sulphides, sulphates, organic matter, and ferrihydrite. Soil formation on such material does not induce a dramatic increase of Zn solubility since efficient scavengers are concomitantly formed in the system. However, Technosols are highly heterogeneous and widely differ from one place to another. The behavior examined in this study is not generic and will depend on the type of Technosol and on the secondary minerals formed as well as on the nature and amount of organic matter.

International audience; In order to evaluate the instrumental parameters for the combined on-line-on-mine-real-time expert system SOLSA (http://www.solsa-mining.eu), portable and laboratory analyses were carried out on coarse granite, sandstone, serpentinized harzburgite and siliceous breccia. Each sample was studied at 5 different surface roughnesses (sonic or diamond drilled, cut, polished at 6 µm and 0.25 µm, sample powders). X-ray diffraction (XRD), portable Infra-Red (pIR) and X-ray-fluorescence (pXRF), and laboratory micro-Raman spectroscopy gave complementary and corroborating results. No major effect on the analyses was noted for the selected surface states. pXRF gave variable results except for the homogeneously serpentinized harzburgite, related to coarse or contrasting grain sizes or pores, small spot size (3 mm) and needs close-to-surface analyses. Portable IR (spot size 1.76 cm 2) is carried out close to surfaces while Raman spectroscopy (1-2 µm) is performed at distance. Sampling strategies have to be defined for each lithology. Major challenges for a combined on-line analysis are to adapt the specificities of the techniques to (1) analyse similar surface areas (from ~2 cm 2 (pIR) to < µm (Raman)), (2) smartly combine all the techniques into a single instrument, and (3) develop appropriate databases to reach a reliable " real-time " outcome results, which can be used for more precise geomodeling, and to rapidly define exploration and beneficiation parameters.

International audience; Within the framework of responsible mining, a SOLSA project (www.solsa-mining.eu) to develop an in-situ tool allowing a quick mineralogical identification of site drill cores has been recently launched. Its objective is to develop new or improved highly-efficient and cost-effective, sustainable exploration technologies. It combines and integrates non-destructive sensors: X-ray fluorescence, X-ray diffraction, infra-red and Raman spectroscopy and 3D imaging. The challenge is to address mixtures of hard and soft rocks, as encountered in a lateritic environment. This paper focuses on the determination of spectral characteristics of laterite drill-cores in the visible to short wave infrared spectral range. One of the most important prerequisites is to study the influence of the surface roughness effect on infra-red spectroscopy analyses. For this purpose, four different rock samples: breccia, sandstones, granite and peridotite, each at five surface states have been considered: as-drilled, as-sawn, polished at 6 µm, polished at 0.25 µm and crushed to powder. The reflectance spectra have been acquired with an ASD Fieldspec 3® spectroradiometer with a contact probe at a sampling surface of 1.76 cm 2 , allowing a spectral analysis at wavelengths from 350 up to 2500 nm. The powder spectrum of breccia presents a higher reflectance than the four other spectra from the same material but weak absorption features. The as-sawn sample presents the higher absorption depth, followed by as-drilled sample and the two polished samples (figure 1). At wavelength 2219 nanometers, a peak of absorption is present. The presence of clay minerals is assumed like illite/sericite with more or less smectite, due to the relatively deep water absorption around wavelength 1900 nanometers. Figure 1: Spectra of Breccia Breccia as-drilled Breccia as-sawn Breccia polished 6 µm Breccia polished 0.25 µm Breccia powder

International audience; Understanding calcium silicate hydrates (CSHs) is of paramount importance for understanding the behavior of cement materials because they control most of the properties of these man-made materials. The atomic scale water content and structure have a major influence on their properties, as is analogous with clay minerals, and we should assess these. Here, we used a multiple analytical approach to quantify water distribution in CSH samples and to determine the relative proportions of water sorbed on external and internal (interlayer) surfaces. Water vapor isotherms were used to explain the water distribution in the CSH microstructure. As with many layered compounds, CSHs have external and internal (interlayer) surfaces displaying multilayer adsorption of water molecules on external surfaces owing to the hydrophilic surfaces. Interlayer water was also quantified from water vapor isotherm, X-ray diffraction (XRD), and thermal gravimetric analyses (TGA) data, displaying nonreversible swelling/shrinkage behavior in response to drying/rewetting cycles. From this quantification and balance of water distribution, we were able to explain most of the widely dispersed data already published according to the various relative humidity (RH) conditions and measurement techniques. Stoichiometric formulas were proposed for the different CSH samples analyzed (0.6 < Ca/Si < 1.6), considering the interlayer water contribution.

Organotin compounds are used as pesticides and fungicides as well as additives in plastics. This study identifies the de novo generation of novel volatile organotins in municipal waste deposits and their release via landfill gas. Besides tetramethyltin (Me(4)Sn), a strong neurotoxin, and 5 previously reported organotins, 13 novel ethylated, propylated, and butylated tetraalkyltin compounds were identified. A concentration of 2-4 μg of Sn m(-3) landfill gas was estimated for two landfill sites in Scotland. The atmospheric stability of Me(4)Sn and methylated tin hydrides was determined empirically in a static atmosphere in the dark and under UV light to simulate night- and daytime conditions. Theoretical calculations were carried out to help predict the experimentally obtained stabilities and to estimate the relative stabilities of other alkylated species. Assuming first-order kinetics, the atmospheric half-life for Me(3)SnH was found to be 33 ± 16 and 1311 ± 111 h during day- and nighttime conditions, respectively. Polyalkylation and larger alkyl substitutes tend to reduce the atmospheric stability. These results show that substantial concentrations of neurotoxic organotin compounds can be released from landfill sites and are sufficiently stable in the atmosphere to travel over large distances in night- and daytime conditions to populated areas.

International audience; Knowledge of the behavior of heavy metals, such as copper and zinc in sediments, is a key factor to improve themanagement of rivers. The mobility of these metals, which may be harmful to the environment, depends directlyon their concentration and speciation , which in turn depend on physico-chemical parameters such as mineralogyof the sediment fraction, pH, redox potential, salinity etc ... (Anderson et al., 2000; Sterckeman et al., 2004; VanOort et al., 2008).Several methods based on chemical extractions are currently applied to assess the behavior of heavy metals insoils and sediments. Among them, sequential extraction procedure is widely used in soil and sediment scienceand provides details about the origin, biological and physicochemical availability, mobilization and transports oftrace metals elements. It is based on the use of a series of extracting reagents to extract selectively heavy metalsaccording to their association within the solid phase (Cornu and Clozel, 2000) including the following differentfraction : exchangeable, bound to carbonates, associated to oxides (reducible fraction), linked to organic matterand sulfides (oxidizable fraction) as well as silicate minerals so called residual fraction (Hickey and Kittrick,1984; Tessier et al., 1979). Consequently sequential extraction method is expected to simulate a lot of potentialnatural and anthropogenic modifications of environmental conditions (Arey et al., 1999; Brannon and Patrick,1987; Hickey and Kittrick, 1984; La Force et al., 1999; Tessier et al., 1979).For three decades, a large number of protocols has been proposed, characterized by specific reagents andexperimental conditions (concentrations, number of steps, extraction orders and solid/solution ratio) (Das et al.,1995; Gomez Ariza et al., 2000; Quevauviller et al., 1994; Rauret, 1998; Tack and Verloo, 1995), but it appearedthat several of them suffer from a lack of selectivity of applied reagents: besides target ones, some of them areable to leach several solid phases.In this context, the aim of the present study is to investigate the effectiveness and the selectivity of differentreagents for metal extraction from target geochemical fraction. It is based on solid analyses with theuse of X-ray diffraction and a scanning electron microscopy (SEM) coupled to a microRaman spectrometerin conjunction with chemical analyses of extracting solutions at each step. This methodology provides theopportunity to assess more accurately the effect of each reagent. The study focuses on extraction of Cu andZn from sediment samples collected at two sites from river banks and characterized by presence of Quartz,Feldspar K, Micas, Kaolinite but with differences regarding accessory phases (pyrite, organic matter, iron oxyhydroxide,calcite). The interaction of the samples with eight different reagents was assessed and compared(Ca(NO3)2 and CaCl2 for the exchangeable fraction; buffered solutions of sodium acetate/acetic acid at pH= 5.5 and pH = 5 for the acido-soluble fraction; hydroxylamine hydrochloride and a solution of ammoniumoxalate/oxalic acid for reducible fraction; hydrogen peroxide and sodium hypochlorite for the oxidizablefraction. In-depth characterization of solid residue at each step allowed proposing the best protocol for both metals.

Bien que nécessaire en très faible quantité pour une bonne physiologie chez la plupart des êtres vivants évolués, certains métaux tels que le cuivre et le zinc sont régulièrement en excès voire en quantité toxique dans les masses d'eau françaises et posent le problème de l'atteinte du bon état chimique ou écologique de ces dernières. Le comportement des éléments depuis leur source d'émission jusque dans les différents compartiments naturels n'est pas toujours maîtrisé et reste une donnée indispensable et préalable à une remédiation. Selon les origines naturelles ou anthropiques et la minéralogie de la fraction sédimentaire, la spéciation des métaux dans la phase solide est variable. Il s'agit d'une donnée mal connue car difficile à caractériser. Cette spéciation conditionne la remise en suspension potentielle des métaux et leur remobilisation sous forme dissoute dans le milieu environnant. Cette étude a consisté à optimiser un protocole d'analyse des sédiments par extraction séquentielle, validé sur le bassin de la Loire. Les verrous sont l'évaluation de l'efficacité et de la sélectivité de différents réactifs afin de définir une suite pertinente et robuste de séquences d'extractions. Une étude minéralogique des sédiments, par diffractométrie des rayons-X, microscopie électronique à balayage et spectroscopie Raman, associée aux analyses chimiques de solutions après chaque extraction a permis de définir ce protocole et d'acquérir la connaissance approfondie de la distribution géochimique des éléments en fonction de 5 classes de constituants ou fractions chimiques : (i) fraction échangeable, (ii) acido-soluble, (iii) oxydable, (iv) réductible ou (v) résiduelle. Ce protocole devrait permettre d'établir une modélisation plus complète des systèmes, à la demande des observatoires soucieux de reconquête de la qualité des milieux.

SEM-EDS and micro-Raman spectroscopy have been combined for material characterization in several recent studies. Switching from one to the other is frequently considered as a problem that cannot be solved using specific solutions. Although both techniques have followed a parallel but very different evolution since their introduction in the early 1930s, the concept of Raman-in-SEM first began in the 1980s and the first commercial systems were marketed in the early 2000s. The two main systems and techniques that have been developed and marketed by three manufacturers are presented and described in this chapter. An evaluation of their advantages and limitations is proposed. A metrological study is then proposed for one of these systems, based on the ‘on-axis’ technique using a curved mirror placed under the SEM pole piece. This study allows a discussion of the performance and limitations of Raman spectroscopy when performed in a SEM. A comprehensive review of published work is provided, although papers are rare in the open literature. The technique is essentially used for controls, expert assessments and high technology applications. Advanced techniques that allow the use of Raman-in-SEM spectroscopy are discussed in detail using application examples taken from different fields in geosciences, materials chemistry or from expert assessments. The conclusions of this study show that Raman-in-SEM spectroscopy is to date the first step in the combination of two well-known and mature techniques enabling the synergy between them to be maximised. Raman-in-SEM spectroscopy is relatively easy to set up and effectively complements the capabilities and efficiency of analytical SEM for material characterization. What are the most likely development perspectives that may be considered for this analytical coupling? Today, commercial systems are limited to only point-level micro-Raman analysis at the micrometre scale. In the near future, developments in both hardware and software will probably allow analysts to acquire Raman maps, or to employ multi-technique analyses based on a combination of data from SEM, EDS Raman, etc. New hardware developments may enhance the spatial resolution of both SEM and Raman spectroscopy.

International audience; The effects of duration (1-100 days) and temperature (20 and 50 °C) were assessed from batch tests for Ca-bentonite mixed with 10 wt.% lime. The pozzolanic processes were monitored over time by 29Si NMR (Cement Concr. Res. 42, 2012), TGA-DTA, XRD and chemical analysis. Modeling considered kinetics and thermodynamics of mineralogical transformations and cation exchange. Kinetic laws were dependent on pH and temperature (Arrhenius energy). Lime hydration occurs within hours, modifying the bentonite exchangeable population and increasing the pH. These alkaline conditions initiate the pozzolanic reactions in a second stage. The rate-limiting step is the dissolution kinetics of the bentonite minerals, i.e. a relatively fast and total consumption of cristobalite in parallel to a long-term slower dissolution of montmorillonite. First C-S-H and then C-A-S-H are formed consequently. Temperature speeds up the pozzolanic reaction kinetics by a factor 5 from 20 to 50 °C, corresponding to an apparent activation energy of 40-50 kJ/mol.

International audience; a b s t r a c t The availability of Raman spectroscopy in a powerful analytical scanning electron microscope (SEM) allows morphological, elemental, chemical, physical and electronic analysis without moving the sample between instruments. This paper documents the metrological performance of the SEMSCA commer-cial Raman interface operated in a low vacuum SEM. It provides multiscale and multimodal analyses as Raman/EDS, Raman/cathodoluminescence or Raman/STEM (STEM: scanning transmission electron microscopy) as well as Raman spectroscopy on nanomaterials. Since Raman spectroscopy in a SEM can be influenced by several SEM-related phenomena, this paper firstly presents a comparison of this new tool with a conventional micro-Raman spectrometer. Then, some possible artefacts are documented, which are due to the impact of electron beam-induced contamination or cathodoluminescence contribution to the Raman spectra, especially with geological samples. These effects are easily overcome by changing or adapting the Raman spectrometer and the SEM settings and methodology. The deletion of the adverse effect of cathodoluminescence is solved by using a SEM beam shutter during Raman acquisition. In con-trast, this interface provides the ability to record the cathodoluminescence (CL) spectrum of a phase. In a second part, this study highlights the interest and efficiency of the coupling in characterizing micromet-ric phases at the same point. This multimodal approach is illustrated with various issues encountered in geosciences.

International audience; A micrometric aluminum-phosphate-sulfate (APS) with an intermediate composition between the minerals woodhouseite (CaAl3(PO4)(SO4)(OH)6) and crandallite (Ca(PO4)2(OH)5⋅H2O) has been identified in a natural sample and characterized using a coupled SEM-microRaman system. The Raman spectrum obtained was characterized by various bands assigned to vibrational modes of sulfate and phosphate units. A comparison with other APS minerals, with different PO4/SO4 ratios, enables some differences to be highlighted, which concern particularly the intensities of some sulfate and phosphate bands. It is established that the intensity of the sulfate bands located at around 653 and 1026 cm−1 decrease as a function of the mole fraction of phosphate in the APS minerals. This correlation reflects well the effect of the substitution of sulfate anions by phosphate anions. In addition, this study has also shown that the use of a coupling system between a SEM and a microRaman spectrometer is a powerful tool to identify micro-minerals of the alunite supergroup occurring in a complex geological sample.

International audience; Raman spectroscopy has been used to study the molecular structure of different natural minerals of the alunite supergroup (AB(3)(XO4)(2)(OH)(6)), with A = K+, Na+, Ca2+, Sr2+, Ba2+, B = Al3+, Fe3+ and X = S6+, P5+. The influence of the ions, in A-, B- and X-sites, is highlighted in the Raman spectra by variations in the position of certain vibrations and is discussed in association with published crystallographic data in order to describe the observed differences. It was found that A-site substitutions are characterized by wavenumber shifts of the vibrations involving hydroxyl groups. The positions of these vibrational bands vary linearly with the ionic radius of the ions in this site. B-site substitutions induce shifts of all bands due to structural modifications that lead to differences in the chemical environment around the hydroxyl and XO4 groups and changes in B-O bond lengths. A correlation showed that these shifts correlate well with the ionic radii of the B-ions. The spectra of compounds containing both sulfate and phosphate groups are described by numerous vibration bands caused by a complex elemental composition and a symmetry change of the XO4 groups. This study has also made it possible to generalize substitution effects on the wavenumbers of several vibrations and show that Raman spectroscopy could be a powerful tool for identifying and distinguishing minerals of the alunite supergroup.