Noel Essey N'guessan

Emmanuel Joussein
email: mail.emmanuel.joussein@unilim.fr

Alexandra Courtin-Nomade

Erwan Paineau

Marilyne Soubrand

Olivier Grauby

Cristina Coelho Diogo

Delphine Vantelon

Pascale Launois

Valentin Robin

Patrice Fondaneche

Sylvie Rossignol

Nathalie Texier-Mandoki

Xavier Bourbon

Emmanuel Joussein

Role of cations on the dissolution mechanism of kaolinite in high alkaline media

Keywords: alkaline activation, kaolinite, XRD, TEM-EDS, XANES, MAS-NMR, dissolution

Kaolinite and its dehydroxylated forms are widely used in industrial applications, particularly in alkaline media. Geopolymers are among the latest applications that are attracting significant interest. Until now, a deep understanding of the dissolution mechanism of kaolinite particles in alkaline media is still lacking. This work aims to well understand the dissolution mechanisms of two references kaolinites (KGa-1b and KGa-2) regarding various 2 M alkali treatment (KOH, NaOH and 50/50 NaOH + KOH) along time and at 80°C through aluminum and silicon leaching.

For this, a wide range of methods have been used, from the determination of [Si] and [Al] in solution to the analysis of solids by combining X-ray diffraction (XRD), Fourier Transformed Infrared (FTIR), X-ray Absorption Near edge Structure (XANES) and Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopies and electronic microscopy observations. The results show that the dissolution rate is higher in the poorly crystallized kaolinites (confirming the role of the crystallinity of the samples towards reactivity in an alkaline media) but also a significant effect of the type of cation (the degree of dissolution following the sequence KOH<NaOH + KOH<NaOH). This dissolution is followed by a change in the speciation of the aluminum from 6-coordinated to a 4-coordinated, as shown by XAS and MAS-NMR results. The dissolution process at the particle scale is different: with KOH, the dissolution is homogeneous, starting from the edges and surfaces, whereas in the case of NaOH, the dissolution is oriented thanks to areas of less coherence.

Highlights:

• The degree of dissolution of kaolinites is linked to the type of alkaline treatment.

• The dissolution rate is higher in the poorly crystallized kaolinites.

• The dissolution is accompanied by a change in the speciation of the aluminum.

• The particle dissolution process is homogeneous in KOH and oriented with NaOH

Introduction

Since the past decades, there has been increasing interest in producing eco-friendly geomaterials from natural and inexpensive materials such as alkali activated materials s.l. or specifically geopolymers. These geomaterials are promising since their properties are comparable to that obtained from Ordinary Portland Cement (OPC) while reducing the energy required during manufacture [START_REF] Habert | An environmental evaluation of geopolymer based concrete production: reviewing current research trends[END_REF]. Geopolymers result from the activation of aluminosilicates sources, such as fly-ash or clay minerals used as precursors, in a high concentrated alkali media (NaOH or KOH) to form free SiO 4 and AlO 4 tetrahedrons at ambient temperatures. The polycondensation (i.e. geopolymerization reaction) results from the reaction of aluminate and silicate dissolved monomers [START_REF] Duxson | Geopolymer technology: the current state of the art[END_REF][START_REF] Van Deventer | Reaction mechanisms in the geopolymeric conversion of inorganic waste to useful products[END_REF]. The tetrahedrally coordinated aluminum carries a negative charge that is counterbalanced by an alkali cation such as Na + or K + . Finally, geopolymers present an amorphous 3D aluminosilicate structure. It is widely accepted that the resulting properties of geopolymer binder depend on the Si/Al ratio of the initial mixture and the kinetic dissolution of the raw aluminosilicate source (i.e., rate and relative amount of Si and Al release in the solution; [START_REF] Catauro | Investigation of the sample preparation and curing treatment effects on mechanical properties and bioactivity of silica rich metakaolin geopolymer[END_REF]. Thus, understanding the chemical reactivity of the Si and Al source during the first steps of an alkali treatment is key to better predict, and control, the properties of geopolymer based materials.

The main source of aluminosilicates in this context is the kaolinite. Kaolinite is a dioctahedral 1:1 clay mineral highly used in a variety of industrial applications (e.g. paper-coating, filler, paint pigment, ceramics, pharmaceutical to cite a few; see large literature such as [START_REF] Murray | Applied clay mineralogy: occurrences, processing, and applications of kaolins, bentonites, palygorskite, sepiolite, and common clays[END_REF]). The theoretical formulae of kaolinite is Al2Si2O5(OH)4 in which one Al octahedral sheet and one Si tetrahedral sheet are linked to each other by sharing apical oxygen atoms from the tetrahedral sheet. One of the main characteristics of most varieties of kaolinite is a defective structure [START_REF] Bailey | Polytypism of 1:1 layer silicates. Hydrous Phyllosilicates Exclus[END_REF][START_REF] Brindley | Relation between Structural Disorder and Other Characteristics of Kaolinites and Dickites[END_REF][START_REF] Sakharov | Modeling powder x-ray diffraction patterns of the clay minerals society kaolinite standards: KGa-1, KGa-1b, and KGa-2[END_REF] resulting in a variety of physical and chemical properties governing its uses [START_REF] Murray | Traditional and new applications for kaolin, smectite, and palygorskite: a general overview[END_REF]. Moreover, it is common to modify the properties of raw material in the way to increase their reactivity by thermal treatment or grinding for instance [START_REF] San Nicolas | Characteristics and applications of flash metakaolins[END_REF]. According to this, kaolinite is conventionally heat-treated to form metakaolin. The metakaolin is the most used material for geopolymers because of its initial Si and Al content (highest alumina content) but also because of its rapid dissolution in alkaline medium which will confer various properties (such as mechanical properties, high fire resistance…) of use to geopolymers [START_REF] Autef | Role of metakaolin dehydroxylation in geopolymer synthesis[END_REF]. The reactivity of metakaolin depends on several factors: (i) the dehydroxylation process of kaolinite as well as the applied temperature, i.e. flash calciner, rotary kiln or vertical multiple-hearth oven from 500 to 800 °C [START_REF] Belver | Chemical Activation of a Kaolinite under Acid and Alkaline Conditions[END_REF], (ii) the purity i.e. the amount of accessories minerals (up to 30% in mixture) such as quartz, feldspars, rutile or anatase [START_REF] Cui | A study on electrical conductivity of chemosynthetic Al2O3-2SiO2 geoploymer materials[END_REF][START_REF] Medri | SiC-based refractory paints prepared with alkali aluminosilicate binders[END_REF], and (iii) the properties of the initial primary kaolinite crystals [START_REF] Kuenzel | Influence of metakaolin characteristics on the mechanical properties of geopolymers[END_REF][START_REF] Rahier | Low-temperature synthesized aluminosilicate glasses[END_REF]. The latter is an important factor depending on the type of deposit and is mainly related to the crystal chemistry of the initial kaolinite [START_REF] Heller-Kallai | Reactions of kaolinites and metakaolinites with NaOHcomparison of different samples (Part 1)[END_REF]. However, the impact of the primary kaolinite crystal chemistry used for the metakaolin processing on their reactivity in alkaline media is still not clear. Therefore, it is essential to fully understand the main factors that drive the reactivity of kaolinites in an alkaline medium through the dissolution of its component species.

The dissolution process of kaolinite under different conditions in terms of alkali type (NaOH or KOH), concentration, pH and temperature has been previously mentioned in the literature. For example, [START_REF] Huertas | Mechanism of kaolinite dissolution at room temperature and pressure Part II: kinetic study[END_REF] studied the dissolution of kaolinite over a pH range of 1 to 13. The authors evidenced a deprotonation of the octahedral surface occurring at high pH value (> 9) along with the formation of an AlO -type surface complex followed by the release of structural Al and the dissolution of kaolinite particles. Interestingly, the octahedral layer also appears to be the main factor limiting the dissolution rate of kaolinite in an alkaline solution (KOH of 0.1 to 4 M; Bauer and Berger (1998)). These findings agree with the previous work of [START_REF] Carroll | Kaolinite dissolution at 25 degrees, 60 degrees, and 80 degrees[END_REF] which evidenced a slower detachment of Si from the kaolinite structure (thus forming SiO-complexes) than that of Al when the clay particles were dissolved. Pentrak et al. (2009) demonstrated, during an alkaline treatment in KOH, that a lower structural ordering and a less regular shape of the crystallites are causing faster dissolution. In terms of cationic effect (e.g. Na + , K + …), it would suggest that the degree of dissolution of Al and Si atoms is significantly higher (40%) in a sodium hydroxide (NaOH) solution than in a KOH solution 22 . Recently, Naderi [START_REF] Naderi Khorshidi | Influence of structural Al and Si vacancies on the interaction of kaolinite basal surfaces with alkali cations: A molecular dynamics study[END_REF][START_REF] Naderi Khorshidi | Molecular dynamics study of the dissolution mechanism of kaolinite basal surfaces in alkali media[END_REF] have studied by molecular dynamics simulation, the modification and/or dissolution of two basal surfaces of kaolinite in various alkaline media (1 M and 5 M) for three different alkaline solutions (containing Na + , K + and a mixture of 50/50 Na + /K + cations) at ambient conditions. The results evidence that Na + and K + induce different dissolution mechanisms related to different dissociation of the surface hydroxyl groups of kaolinite particles.

The authors also explained that a synergistic effect of both cations is effective in the case of the 50/50 mixture leading to more surface structure distortion.

Until now, a deep understanding of the dissolution mechanism of kaolinite particles is still lacking. It requires considering both the crystallochemistry of kaolinite, the nature of cation (containing Na + , K + and a mixture of Na + /K + cations) and their impact onto the solid structure. It is essential to understand how kaolinite reacts (dissolves) in an alkaline medium in order to better understand geopolymerization reactions (quantity of Si and Al species in solution, speciation of Al i.e. (IV)-or (VI)-coordinated) and the choice of aluminosilicate mineral raw material. Here, we proposed to better understand the dissolution mechanisms of two references kaolinites (KGa-1b and KGa-2) regarding various 2 M alkali treatment (KOH, NaOH and 50/50 NaOH + KOH; type of alkali solutions was chosen according to the geopolymerization literature; see for example [START_REF] Aldabsheh | Dissolution behavior of Jordanian clayrich materials in alkaline solutions for alkali activation purpose[END_REF] or [START_REF] Xu | The geopolymerisation of alumino-silicate minerals[END_REF]) along time and at 80°C through aluminum and silicon leaching. These two references kaolinites, KGa-1b and KGa-2, differ in terms of structural disorder. In this framework, we studied the release of both Al and Si from kaolinite platelets by monitoring the structural evolution of the solid phase by combining X-ray diffraction (XRD), Fourier Transformed Infrared (FTIR), X-ray Absorption Near edge Structure (XANES) spectroscopies and microscopy observations. Altogether, our results unravel (i) the importance of kaolinite crystallochemistry on its chemical reactivity, (ii) the effect of the type of cation toward dissolution rates and associated mechanisms and then (iii) the occurrence and effect on dissolution rates and solid modification of different dissolution mechanisms involved in alkaline media treatments.

Material and Methods

Background onto reference kaolinites

Two reference kaolinites referred as KGa-1b and KGa-2 hereafter were provided by the Clay Mineral Society. These kaolinites are representative of commonly occurring, natural kaolinite materials and are distinguished by phase purity and availability [START_REF] Sakharov | Modeling powder x-ray diffraction patterns of the clay minerals society kaolinite standards: KGa-1, KGa-1b, and KGa-2[END_REF]. These two samples are well known in the literature (for example reader referred to the baseline studies of the Clay Minerals Society source clays in [START_REF] Costanzo | Baseline studies of the clay minerals society source clays: preface[END_REF]), the main properties (chemical analysis and main physico-chemical properties) are reported in the Table SI 1 in Supplementary Information. The initial mineralogy is dominated by kaolinite (96 % for KGa-1b and KGa-2) with some accessory minerals, i.e. 3% of anatase and 1% of quartz for KGa-1b; 3% of anatase and 1% of mica and/or illite and quartz for KGa-2. The presence of other silicate minerals than kaolinite, e.g. quartz, may imply a Si/Al ratio slightly different than 1 in agreement with chemical analyses reported in Table SI 1.

Alkali treatment experiment

The treatment was performed at 80°C in three different alkali media (pure KOH, pure NaOH, or a mixture of KOH + NaOH 50/50) at the same 2 M concentration in OH (ca pH 14). Briefly, KOH and NaOH pellets (VWR analytical reagents grade) were dissolved in double-deionized water. 300 mg of KGa-1b or KGa-2 were mixed with 30 ml of 2 M alkali solutions in Teflon vessels.

The mixtures were shaken in a Memmert water-bath stirrer at 80°C at various time steps (1, 3, 6, 12, 24 h). Each experiment was realized in sacrificial mode. After shaking, the liquid and the solid phases were separated by centrifugation at 2734 g for 5 min at room temperature. The supernatants were filtered at 0.45 µm from cellulose acetate filters and diluted in acidic media (HNO3 2%) prior to analysis. The solid residues were rapidly washed twice by dispersion in deionized water and centrifugation at 4000 rpm for 5 min to stop alkali treatment and dried at 45°C in an oven for structural and microscopic investigations. All the experiments were carried out in duplicate.

The Si and Al chemical analyses were conducted on a microwave plasma-atomic emission spectrometer (MP-AES, Agilent MP 4100) coupled with a high-performance liquid chromatography (HPLC) setup, modified for analyzing strong alkali solutions. The measurement errors were less than 10% based on reproducibility tests.

Characterization of solid phases

XRD was carried out on a Bruker D8 diffractometer operating with Cu Kα radiation (λ=0.154 nm). The samples were prepared as disoriented powders and scanned between 2 -65 °2θ with a 0.02 °2θ step for 1 s per step. X'Pert Highscore software was used for qualitative identification of minerals. The crystallinity index of each samples was estimated using the Hinckley index according to [START_REF] Plançon | The Hinckley index for kaolinites[END_REF]; it is based on the ratio of the sum of the intensity of the (1ī0) and (1ī1) reflections measured from the inter-peak background, and the intensity of the (1ī0) peak determined from the general background. FTIR spectroscopy was performed on a Perkin Elmer spectrometer using attenuated total reflectance (ATR) in the middle infrared (MIR) region (4000 -600 cm -1 ) and each final spectrum is the average of 5 scans. The theoretical resolution of the device is 2 cm -1 . Omnic software was used for spectrum analyses.

Al and Si K-edges XANES experiments were undertaken at LUCIA beamline (Soleil synchrotron, France). The X-ray beam was monochromated using a pair of KTP (011) crystals.

The energy was calibrated at the first inflexion point of the Al K-edge of an aluminum foil (1559 eV) or of a silicon foil for the Si-K-edge (1839 eV). Spectra were collected in steps of 2 eV below the edge, of 0.2 eV in the edge region and of 1 eV behind the edge, at a counting rate of 2 s per step. Data were recorded in fluorescence mode using a mono-element silicon drift diode detector and corrected for the detector dead time. Data processing, normalization and analysis were performed with the Athena software [START_REF] Ravel | ATHENA and ARTEMIS: interactive graphical data analysis using IFEFFIT[END_REF] 27 Al (I = 5/2) MAS NMR spectra were obtained by using short pulses (<π/8). Nutation curves were first established by using a solution of 1M Al(NO3)3 (t90°( 27 Al) = 3.2 μs, Recycle delay = 0.5s, number of scans = 6000-12000). 2D 27 Al 5QMAS NMR spectra [START_REF] Medek | Multiple-Quantum Magic-Angle Spinning NMR: A New Method for the Study of Quadrupolar Nuclei in Solids[END_REF] were obtained by using an amplitude modulated Z-filter experiment (p1-t1(5Q evolution)-p2-τ-p3-t2(acquire) [START_REF] Amoureux | Z Filtering in MQMAS NMR[END_REF]. The optimized pulse lengths of the 5Q excitation (p1) and reconversion (p2) were p1 = 4.5 μs and p2 = 1.5 μs, respectively, implemented with an rf field of 55 and 165 kHz, whereas the soft π/2 Z-filter (p3) was set to 6.5 μs, which was delivered with an rf field of ∼40 kHz (recycle delay = 0.2s, number of scans = 6000). 27 Al NMR chemical shifts were referenced to a 1M solution of Al(NO3)3, respectively. All decompositions of spectra were performed using the DMfit software [START_REF] Massiot | Modelling one-and two-dimensional solid-state NMR spectra[END_REF], available free of charge online. For 27 Al spectra, previous studies have clearly demonstrated the combined role of quadrupolar interaction and CSA on the line shapes, especially at high magnetic field [START_REF] Papulovskiy | Theoretical and experimental insights into applicability of solid-state 93 Nb NMR in catalysis[END_REF]. Lorentz/ Gaussian (L/G) line shapes were used for AlIV sites end the int2QUAD DMfit module was used under the assumption of finite rotation frequency for the central transitions for AlVI sites. The following parameters were taken into account for each 27 Transmission Electron Microscope (TEM) using a JEOL JEM 2011 (CiNAM). For TEM observations, samples were suspended in water and left to dry on gold and copper grids. The analyses were conducted at the accelerating voltage of 200 kV. The parameters were 50 000× magnification, 20° tilt angle toward the EDX detector, energy range of 40 keV, corrected counting time of 30 s, constant beam density ∼63.5 pA.cm -2 . Elements were quantified using the Bruker AXS TEM line mark data semi-quantification procedure [START_REF] Berthonneau | Impact of swelling clays on the spalling decay of building limestones: insights from X-ray diffraction profile modeling[END_REF]. EDX chemical analyses were performed on 20 individual particles. The size of the particles (mean from 30 particles) was manually measured on micrographs using ImageJ software. reflecting a decrease of the dissolution rate with time. However, the two kaolinites do not react in the same way after 12h since in the case of KGa-2, it seems that there is a stabilization of the dissolution which is not the case for KGa-1b except for a mixed alkaline treatment. The dissolution phenomena observed by Bauer et al. (1998) on well-crystalline kaolinite at 80°C in 2M KOH evidenced that the change of slope occurs after 3-4 days when the concentrations of Si and Al are greater than 7 mmol/l. In our case the reaction is faster with a clear change of slope after 6hand Si and Al concentrations reaches values of 40 and 50 mmol/l for KGa-1b and KGa-2 respectively. A drastic decrease of [Al] and [Si] in solution is observed in the case of a NaOH treatment after 6 h, this effect being more pronounced and very rapid in the case of KGa-2 compare to . This feature can be attributed to a re-precipitation phenomenon of solid(s) phase(s) that control concentration of Si and Al in solution (see discussions in section 3.2 Mineralogical evolution of kaolinite dissolution in high alkali media). Up to 6h, NaOH and KOH + NaOH mixtures seem to be the most efficient for the dissolution of both kaolinites (about 75% ± 2% of total Al and Si are released by KGa-1b and 82% ± 2% released by KGa-2). However, after 6 hours, there is a secondary phase precipitation that results in a decrease of Si and Al concentrations in solution. Note that such decrease in aqueous Si and Al concentrations does not mean that the dissolution reaction of the kaolinite is limited, and the reverse may be the case with an increase of the kaolinite dissolution as the thermodynamic equilibrium may not be reach due to the involvement of aqueous Si and Al in a side reaction, i.e. precipitation of secondary phases.

Results and discussion

Alkali dissolution kinetics of kaolinites samples

With KOH treatment, 60 to 70% (± 2%) of total Al and Si are released in solution from both kaolinites. The orders of efficiency of alkaline treatment for the kaolinite dissolution follows: KOH < KOH + NaOH ≤ NaOH, taking into consideration a duration up to 6h since the reprecipitation occurs after. The results relative to the main efficiency of NaOH are in accordance with others study on the dissolution of different industrial aluminosilicate minerals in similar alkali media [START_REF] Panagiotopoulou | Dissolution of aluminosilicate minerals and by-products in alkaline media[END_REF]Xu and van Deventer, 2003). However, this contrasts with the results from molecular dynamic simulations of Naderi Khorshidi et al. ( 2018) that suggest the cation with low charge density K + encouraged more dissociation of the aluminate groups than the Na + one.

Si/Al molar ratio is calculated at each time step for all experiments, and the results show that the ratio is < 1 (0.80 < Si/Al < 0.98) regardless of the type of kaolinite at t < 6h, then stabilizes around 1 (0.99 ± 1) between 6 and 12 h for most of the experiments (Figure SI 2 Supplementary Information). Note that the Si/Al ratio of a theoretical kaolinite is closed to 1. To conclude, these data show that the rapid dissolution is incongruent at first during the alkaline attack and then becomes congruent over time.

Mineralogical evolution of kaolinite dissolution in high alkali media

XRD and FTIR measurements

X-ray diffractograms were acquired on both initial materials and the alkali treatment residues (Figure 2) to characterize any significant changes of the solid phase during the alkali treatment.

The two kaolinite samples differ essentially in terms of crystallinity, i.e. amount and nature of structural defect. KGa-1b is a low-defect kaolinite (Hinckley index = 1.01) whereas KGa-2 is the high-defect one (Hinckley index = 0.37). The effect of the crystallinity results in higher values of CEC and SSA for KGa-2, the high defect one, compared to the KGa-1b. Two types of structural disorder can be considered in KGa-1b and KGa-2: one for KGa-2 from random interstratification of thin enantiomorphic blocks and a low ordered population of crystallites in which layer displacements occur in relatively high proportions; a second one for KGa-1b, corresponding to the highly ordered population of crystallites, due to structural periodicity seldom disturbed by isolated stacking faults [START_REF] Sakharov | Modeling powder x-ray diffraction patterns of the clay minerals society kaolinite standards: KGa-1, KGa-1b, and KGa-2[END_REF].

A significant decrease in post-treatment diffraction peaks is observed regardless of the type of kaolinite and the type of reflections, i.e. basal (00l) or (hkl), indicating changes in the diffracting domain size distribution and implying that the crystal shape changes. These results are in accordance with those of Pentrak et al. (2009) who observed similar decreases of the diffraction peaks along alkaline treatment with 4 M KOH solution. The alteration of the diffraction peaks is in accordance with kinetic data that clearly evidences a dissolution of crystallites in an alkaline medium. It results in a decrease over time of the Hinckley crystallinity index and a decrease in the ratio of (060)/(001) reflection band which may be similar to a reduction in coherence in the b direction of the kaolinite platelets. As expected, KGa-2 also shows a greater extent of dissolution, i.e. alteration, probably due to the lower crystallinity, so the decrease is thus more pronounced. Actually, it is not possible from XRD data to define the type of alteration and the mechanisms involved. In the case of the sodium treatment (NaOH 2 M), XRD measurements also evidence the presence of a new solid phase with several Bragg peaks corresponding to 6.34, 4.44, 3.64, and 2.56 Å inter-planar distances (Figure 2) related to a losod compound according to the JCPDS file 31-1269 (theoretical formulae Na12Al12Si12O48, 18 H2O). This mineral phase is a polytype of hydroxysodalite and basically belonging to zeolite mineral group, explaining the decrease of the [Al] and [Si] in chemical analysis after 12h of contact time (Figure 1).

The zeolite precipitation is also pointed out by SEM observations (Figure SI 3 Supplementary information) and after by FTIR (Figure 3). The formation of zeolites particles, uniform in size and shape whatever the initial kaolinite sample, with the appearance of "wool ball" are noticeable for both kaolinites (KGa-1b and KGa-2, Figure SI 3). This is in accordance with the literature where several authors (e.g. [START_REF] Lin | Crystallization of JBW, CAN, SOD and ABW type zeolite from transformation of meta-kaolin[END_REF][START_REF] Singer | Cation Exchange Properties of Hydrothermally Treated Coal Fly Ash[END_REF] have obtained this type of zeolite in concentrated sodium alkaline medium (> 3.5 M NaOH) at room temperature. In our case, losod is obtained at a lower initial NaOH concentration because the reaction takes place at 80°C, which facilitates precipitation in lower concentrations. [START_REF] Sieber | Formation and Properties of Losod, a New Sodium Zeolite[END_REF] showed that zeolite-like losod crystallized only from mixtures with low sodium contents (0.25 ≤ Na/Al ≤ 1 and Si/Al ≤ 1). In this experiment, the alkali treatment of kaolinite in NaOH leads to Na/Al = 0.63 and Si/Al = 1, confirming the possibility for zeolite to precipitate. Na + is then easily and rapidly recombined with Al and Si in solution leading to zeolite precipitation. Finally, the presence of zeolites-like or other phases resulting from precipitation in a basic medium was not observed in the case of KOH or NaOH + KOH. This means that the presence of K in the system inhibits the precipitation of zeolite under these experimental conditions. However, Bauer et al. (1998) have observed the precipitation of phillipsite-type zeolite in KOH 2M at 80°C but after 30 days of time contact of a kaolinite sample. This difference may be related for the authors to the presence of accessories minerals in the initial sample acting as precursors, which are not present in the KGa-1b and KGa-2 samples. ATR-FTIR measurements in the MIR range are reported in Figure 3. The focus is previously done on the case of KOH or KOH + NaOH treatments for 24 h. The data evidences (i) in the OHstretching region, a decrease of the ν1 band (3690 cm -1 ) coupled with a slight decrease in absorbance of the ν2 and ν3 bands located at 3669 and 3650 cm -1 . These three bands are respectively due to the 3 inner surface hydroxyls. The ν1 and ν2 bands are the coupled antisymmetric and symmetric vibrations [START_REF] Brindley | Relation between Structural Disorder and Other Characteristics of Kaolinites and Dickites[END_REF] whereas the ν3 is due to symmetry reduction from an inner surface hydroxyl [START_REF] Farmer | The infra-red spectra of layer silicates[END_REF]. The fourth band ν4 at about 3620 cm -1 is attributed to the inner hydroxyl [START_REF] Johnston | Polarized Single-Crystal Fourier-Transform Infrared Microscopy of Ouray Dickite and Keokuk Kaolinite[END_REF][START_REF] Rouxhet | Attribution of the OH stretching bands of kaolinite[END_REF];

(ii) in the Al-bending vibration range (δAl2-OH; 935 and 912 cm -1 corresponding to the OH of inner-surface hydroxyl groups and the OH deformation of inner hydroxyl groups), no difference is effective between spectra of both treated kaolinite; (iii) in the case of the absorption band near 1000 cm -1 related to a polymeric tetrahedral aluminosilicate network [START_REF] Farmer | Characterization of the chemical structures of natural and synthetic aluminosilicate gels and sols by infrared spectroscopy[END_REF], a slight increase of the band located at 1005 cm -1 is observed along alkali treatment. It was reported in the literature that this band can be relative to an excess of AlO4 units in the aluminosilicate framework [START_REF] Pentrák | Acid and alkali treatment of kaolins[END_REF]. Finally, in highly alkaline solution (KOH or a mixture KOH + NaOH), all the FTIR results indicate the OH bands alteration, especially for the 3 inner surface hydroxyls, and the fact that the Al coordination could evolved from octahedral to tetrahedral coordination specifically in the case of the lower crystalline kaolinite [START_REF] Sanz | Aluminum-27 and Silicon-29 Magic-Angle Spinning Nuclear Magnetic Resonance Study of the Kaolinite-Mullite Transformation[END_REF][START_REF] Singh | Experimental Transformation of Kaolinite to Halloysite[END_REF]. We can thus hypothesize that the dissolution is preferentially located at the edge of the particle as well as on the inner OH surface, corroborating the dissolution data obtained before. Indeed, the experimental results are consistent with a dissolution mechanism involving inward movement of a dissolution front from crystal edges and the corner than the surface [START_REF] Noiriel | Direct Determination of Dissolution Rates at Crystal Surfaces Using 3D X-ray Microtomography[END_REF][START_REF] Rozalén | Experimental study of the effect of pH on the kinetics of montmorillonite dissolution at 25°C[END_REF]. During the dissolution, the dissociation of the OH groups could be related to the modification in the Al coordination probably with a change from the octahedral (6-fold, AlO6) to tetrahedral (4-fold, AlO4) configurations.

By contrast, the spectra of kaolinites treated with NaOH exhibit important changes. Starting from the raw kaolinite spectra, the signal of the OH stretching bands drastically decreases. The region of Si-O modes is totally redefined by the appearance of a single and broad band at 938 cm -1 with shoulders at 1001 and 1025 cm -1 . Moreover, a broad band at 3400 cm -1 and a band at 1650 cm -1 appear in the spectra corresponding to the vibrations (stretching and bending respectively) of water. Unfortunately, such signal in the 1100-700 cm -1 range is characteristic of the overlaps signal of different mineral phases (i.e. zeolite as already highlighted from the XRD profiles plus kaolinite). Consequently, it is difficult to follow the dissolution effect on kaolinite in this range due to (i) the overlapping of zeolite spectra, (ii) the infrared spectra decomposition which is not trivial and (iii) the insufficient sensitive decomposition to observe structural modification.

Change in the Al and Si speciation from XANES

To understand the effects of the alkaline treatment on kaolinites, XANES was undertaken to unravel the evolution of the atomic environment of Si and Al through the dissolution process.

Figures 4 and5 present respectively Al and Si-K-edge XANES measurements obtained on kaolinite samples before and after alkaline treatment at 24h. The Al K-edge spectra (Figure 4) have a similar structural environment corresponding to an isoelectronic AlO6 9-clusters displaying typical features for 1:1 clays with a low site symmetry and Al octahedrally coordinated linked by the edge to form a dioctahedral gibbsitic layer (2/3 octahedral sites with Al and a vacancy). The weak shoulder at 1565 eV is assigned to the allowed transition of Al 1s electrons to antibonding ttu state (p-like transition) [START_REF] Ildefonse | Aluminium X-ray absorption Near Edge Structure in model compounds and Earth's surface minerals[END_REF][START_REF] Li | Al K-edge XANES spectra of aluminosilicate minerals[END_REF]. The white line is located at 1570 eV and the peaks located at 1567 eV (before multiscattering effect) and 1574 eV (post-edge region) may be due to the transitions of Al 1s electrons to t2g and eg states (d-like transition), respectively. Finally, two broad components also occur in the post-edge region at 1578 eV and 1589 eV due to multi-scattering effect and the first EXAFS oscillation, respectively. According to the alkali treatment effect, the main modification consists in the increase of the component at 1564 eV whatever the treatment used (increasing drastically in the case of NaOH). The Al K-edge energy shift (1569 to 1564 eV) may be directly attributed to the change in coordination number of Al [START_REF] Ildefonse | Aluminium X-ray absorption Near Edge Structure in model compounds and Earth's surface minerals[END_REF][START_REF] Li | Al K-edge XANES spectra of aluminosilicate minerals[END_REF]. The presence of Al(IV) near 1564 eV is evidenced in the case of NaOH or NaOH + KOH treated samples, and finally the Al(VI) at 1569 eV (Figure 4). Note that the presence of Al(V) cannot be excluded as its signal near 1564 eV is combined with that of Al(IV) and Al(VI) 49 . XANES results suggest the presence of Al(IV) after 24h of alkali treatment whatever the treatment used. This fact is clearly evidenced for NaOH treatment and mainly in the case of the KGa-2 sample. However, the resulting spectra in the case of the NaOH treatment (Figure 4) reflects the overlap of zeolite-like mineral with kaolinite one, making difficult to decipher the contribution of one to another to the Al speciation. Indeed, the coordination of Al in zeolite is mainly 4-coordinated (as already observed in the case of the orthoclase mineral) inducing the high amount of Al(IV); it is thus difficult to conclude about the direct effect on Al speciation evolution after 6h (from XRD data) within the kaolinite during NaOH treatment.

The Si K-edge spectra of the kaolinite alkali treated (Figure 5) are qualitatively very similar in accordance with the literature [START_REF] Li | Al K-edge XANES spectra of aluminosilicate minerals[END_REF]. All Si K-edge spectra of kaolinite display a strong edge maximum at 1846 eV which can be ascribed to the 3s transition [START_REF] Ildefonse | Aluminium X-ray absorption Near Edge Structure in model compounds and Earth's surface minerals[END_REF]. The poorly resolved features 3p and 3d-like transitions at 1849 and 1853 eV is due to the scattering atoms within the tetrahedral layer, and finally the multiple scattering effect (1851 eV) from the more distant shell atoms. No change in the morphology of the spectra is observed. It may be interpreted in a similar way considering that Si present similar structural environment and SiO4 4- clusters. Therefore, regardless of the type of treatment (KOH and NaOH + KOH) no (or very little) modification of the tetrahedral layer of kaolinites is effective. The environmental change in the case of NaOH treatment is related to zeolite precipitation (see before) in which the environment of silicon is modified compared to that of kaolinite.

Overall, our XANES measurement at the Si and Al K-edge reveal a strong modification of the Al octahedral layer along the dissolution effect favouring the transformation of Al(VI) into Al(IV or V) regardless of the type of treatment. However, in the case of NaOH treatment, the change in speciation is probably also linked to the precipitation of zeolite (Al speciation being in fourcoordinated environment). Moreover, there is no modification related to tetrahedra local organization (tetrahedral layer). Consequently, the latter dissolves with release of Si without modification of its environment.

Quantification of the Al tetracoordinated from 27Al MAS-NMR

To resolve the different Al sites, 27 Al MAS NMR experiments and multiple-quantum MAS techniques have been utilized and are reported in Figures 6 and7 respectively for the two kaolinites, each treatment and for 24h of time. The signal observed at 7.3 and 7.6 ppm for KGa-1b and KGa-2 is consistent with a six-coordinated Al in accordance with the literature [START_REF] Mackenzie | Multinuclear Solid-State Nuclear Magnetic Resonance of Inorganic Materials[END_REF] (signal between 10 to +15 ppm). This peak is close to the true isotropic chemical shift (δiso). The position of this resonance is constant whatever the treatment and the kaolinite used, but it seems that its intensity drastically decreases in the case of NaOH treatment with the increase of Al-four coordinated resonance. For the raw kaolinite, a weak second peak located at 70.1 and 69.8 ppm for KGa-1b and KGa-2 is attributed to the presence of a four-coordinated Al-O species [START_REF] Mackenzie | Multinuclear Solid-State Nuclear Magnetic Resonance of Inorganic Materials[END_REF], and correspond to the presence of accessories mineral, as crandallite in the samples [START_REF] Chipera | Baseline Studies of the Clay Minerals Society Source Clays: Powder X-ray Diffraction Analyses[END_REF]. This resonance seems to be stable whatever the treatment and time except after 24h. After this period of NaOH + KOH and KOH treatment, a new peak located near 60 ppm is observed and attributed to the presence of four-coordinated Al-O species directly linked to the kaolinite structure. The contribution of the peak (corresponding to the quantification of Al(IV)) represents 1.9 and 12.9 % of the total Al for KGa-1b and KGa-2 after NaOH + KOH treatment, whereas the contribution increases respectively to 8.5 and 14% after KOH treatment.

In the case of NaOH treatment after 24h, 27 Al MQMAS NMR experiment was performed to disentangle the contributions from alkali-treated kaolinite, zeolite and crandallite (Figure 7). The decomposition of the signal clearly shows four resonances in the 4-coordinated Al region whatever the type of kaolinite. The peak at about 68 ppm is attributed to crandallite [START_REF] Kim | Application of MAS NMR spectroscopy to poorly crystalline minerals: viséite[END_REF]. The contribution at 60 ppm is assigned to Al(IV)-coordinated linked to the kaolinite particles and corresponds to 22.7 and 61.7% of Al (IV) for KGa-1b and KGa-2 respectively. Finally, the NMR signals related to the Al(IV) component from zeolites appear at 56 and 58 ppm, corresponding to q 4 Al atoms with only Si neighbors, and a contribution at 63 ppm ascribed to q 3 Al atoms, i.e. with three Si atoms and one neighboring OH group [START_REF] Dedecek | Synthesis of ZSM-5 Zeolites with Defined Distribution of Al Atoms in the Framework and Multinuclear MAS NMR Analysis of the Control of Al Distribution[END_REF]. The investigations realized from NMR analysis clearly evidenced that the alkali treatments induce the change in Al speciation in kaolinite in accordance to XANES experiments: change of Al speciation from (VI) to (IV) but no evidence was done for the presence of Al(V)coordinated. Moreover, the integration of each contribution shows the importance of (i) kaolinite crystallinity toward dissolution reactivity in alkaline treatment: the KGa-2 being more reactive, inducing the transformation up to 61.7% of Al(IV) after NaOH treatment; and (ii) the role of cation since NaOH treatment is more effective compare to KOH and KOH + NaOH mixtures.

Explanation of the dissolution process toward cationic effect in high alkali solution

To study more precisely the effect of particle dissolution in various alkaline media, TEM investigations were carried out at the particle scale (Figure 8). Before the alkali treatment, TEM images of both KGa-1b and KGa-2 (Figures 8a and8e) evidence the recognizable platy and hexagonal crystals of kaolinite. The mean size of the KGa-2 is lower than for KGa-1b, in accordance with the literature [START_REF] Gormley | The in Vitro cytotoxicity of some standard clay mineral dusts in the respirable size range[END_REF]. After 24 h of treatment with 2 M KOH (Figures 8b and8f), the initial hexagonal shape of kaolinite particles is no more observable whatever the kaolinite samples. Anisotropic dissolution can be observed with apparent higher dissolution of clay minerals crystal edges than basal surfaces (no clear etch pits visible on basal planes or retreat), with a rather homogeneous retreat of all the edges. The retreat of the crystal edges lead to the presence of sub-rounded platy particles instead of the well-shaped platy polyhedron present in the initial material. Affects. This mode of dissolution, with a fastest dissolution of edges (and corners) of the crystal edges, is quite classical as evidenced by local measurements at the mineral surfaces for other types of minerals (e.g. on carbonates [START_REF] Noiriel | Direct Determination of Dissolution Rates at Crystal Surfaces Using 3D X-ray Microtomography[END_REF]). However, due to this dissolution effect, it is almost impossible to determine quantitatively an average length and width of the particles. In the case of 2 M NaOH treatment (Figures 8c and8g), the dissolution of kaolinite crystals is completely different. Indeed, the overall hexagonal shape of the kaolinite crystals is better preserved, but the dissolution is highly anisotropic, with different dissolution mechanisms from edge to edge with elongated etch pits formed from some crystal edges and all oriented in the same direction, and with a retreat of other edges in a lesser extent. This phenomenon looks like etch pits observed during the dissolution of several silicates like quartz [START_REF] Brantley | Dissolution at dislocation etch pits in quartz[END_REF] or feldspars [START_REF] Pollet-Villard | Influence of etch pit development on the surface area and dissolution kinetics of the orthoclase (001) surface[END_REF] among others. However, even if the formation of etch pits were previously describes on the basal planes of phyllosilicates [START_REF] Kurganskaya | Does the stepwave model predict mica dissolution kinetics?[END_REF][START_REF] Kurganskaya | A comprehensive stochastic model of phyllosilicate dissolution: Structure and kinematics of etch pits formed on muscovite basal face[END_REF], this is the first time that this kind of dissolution process is observed in the case of clay minerals. These oriented dissolutions originate from structural properties of the crystal and could be linked to the activation of defects like dislocations, vacancy sites in octahedral sheets or sites where Al ions could have been substituted by Fe ions (possible substitution about 0.01 Fe atoms per half-cell) and propagation of the dissolution along 2D defects or following chains of weaker bonds into the crystal lattice. The mean length and width of dissolution pits are 192 nm versus 53 nm for KGa-1b and 146 nm versus 36 nm for KGa-2 respectively (±5%). These differences can be explained by the initial size of kaolinite particles inducing differences in term of dissolution pits morphology. In fact, there must be a critical size of dissolution channels. In the case of large particles with good crystallinity, dissolution is slow, and channels can spread over a large surface area along uninterrupted series of bonds in the crystal lattice. On the contrary it is supposed that the smaller and poorly crystalline particles present pits limited in size either because the propagation of the dissolution along a specific defects or chain of bonds will be interrupted by changes in the crystal lattice, or because of the quick coalescence of small pits before they can spread, which lead to a complete dissolution of the external parts of the particles (which is in agreement with the higher dissolution rate observed for KGa-2 kaolinite, see Figure 1 and previous discussions). As a result, the apparent pits sizes for KGa-2 are smaller. With 2M KOH + NaOH treatment (Figures 8d and8f), a combination of both phenomena is observed, i.e., the hexagonal shape vanishing and the two types of alteration: homogeneous retreat from the edge as observed in KOH treatment, and oriented dissolution from some edges as observed in NaOH treatment. By calculating the number of Al and Si atoms per half kaolinite cell from EDX microanalyses obtained by TEM on discrete kaolinite particles after 24 hours of treatment (Figure 9), it is found that there are differences according to the treatments. The evolution is linear, which implies a relationship between the different treatments on kaolinites dissolution without ruling out a different dissolution mode in accordance with TEM photography and dissolution kinetics.

Indeed, in the case of a KOH-based treatment, the Al content in the particles decreases with an increase in Si compared to a particle that has not undergone treatment, whereas in the case of NaOH the shift is less significant but results in a decrease in Si with an increase in Al. As expected, the changes induced during the mixed treatment (NaOH + KOH) are intermediate. The fact that both dissolution modes (isotropic and anisotropic) are observed in treatment of kaolinites with KOH + NaOH confirm the effect of the cation (K + or Na + ) during the alkali treatment.

Finally, in the case of KOH treatment, the isotropic dissolution seems to be more intense at the level of the octahedral layer inducing a decrease in the quantity of Al(VI)-coordinated. In the case of NaOH, the dissolution being oriented, the modifications are less intense since they are located on specific zones. Even if the octahedral layer is destroyed, the tetrahedral layer is also strongly altered, favoring the surface dissolution of kaolinite. For this reason, the amount of Si is lower after a NaOH treatment than after a KOH treatment. Moreover, this type of dissolution probably induces the change in the speciation of Al located at the edge of each oriented dissolution zone.

Finally, the dissolution of the octahedral layer acts as an activator for the dissolution of the tetrahedral layer. Consequently, the dissolution of kaolinite seems to be due to the first deprotonation of Al group and thus enhancing negative charges on both Al and Si sites. When the mechanism is engaged, the dissolution occurs similarly whatever the type of layer. On the other hand, the crystallinity of kaolinite seems to influence the progress of this dissolution. Indeed, in the case of a turbostratic stacking (lower crystallinity; KGa-2) the number of defects and access paths for dissolution is greater, whereas in the case of a kaolinite of good crystallinity, it is more difficult to balance the dissolution process in a congruent manner. According to the literature, the congruence or not of the dissolution of kaolinite is a matter of controversy. Indeed, the potentiometric titration of surface speciation of kaolinite shows that the kaolinite dissolves congruently at pH value < 4 and pH value > 11 (Bauer et al., 1998;[START_REF] Huertas | Mechanism of Kaolinite Dissolution at Room Temperature and Pressure: Part 1. Surface Speciation[END_REF][START_REF] Pentrák | Acid and alkali treatment of kaolins[END_REF]. Moreover, [START_REF] Carroll-Webb | A surface complex reaction model for the pHdependence of corundum and kaolinite dissolution rates[END_REF] and [START_REF] Xie | The effect of alkali metals on the formation of geopolymeric gels from alkali-feldspars[END_REF] suggested from calculation and potentiometric titrations that the dissolution is probably nonstoichiometric at first and then followed by a long-term, steady state congruent dissolution then in accordance with this study, whereas Naderi Khorshidi et al. ( 2018) evidence a congruent dissolution over the time from molecular dynamic. The authors explained that the dissolution mechanism of kaolinite basal surfaces in alkali media as follow: the Na + solution triggers more surface hydroxyl groups to dissociate from the octahedral surface than the K + solution but in contrast, K + solution results in greater dissociation of the aluminate groups than the Na + solution. They attributed the different dissolution mechanism of the two cations to their difference in the charge density. Indeed, owing to the smaller size of Na + (i.e., higher charge density), Na + exhibits stronger interaction with O - (or OH groups) on the partially deprotonated octahedral surface and therefore, increases the tendency of the dissociation of O -(or OH groups), not the moieties containing Al atom. Moreover, [START_REF] Carroll-Webb | A surface complex reaction model for the pHdependence of corundum and kaolinite dissolution rates[END_REF], through their work on the surface complex reaction model for the pH-dependence of kaolinite dissolution, show that the measure of specific surface area obtained from SEM is smaller than the BET one after dissolution experiments. The authors suggest the presence of small channels (not shown in their paper but suggested) along kaolinite edges which are accessible to Kr adsorption. According to this work and since Na + with a higher charge density induced more hydroxyl groups to dissociate than K + , it is possible to hypothesize that protons or hydroxyl ions can penetrate easily between kaolinite layers starting from these channels inducing an increase of oriented dissolution.

Conclusion

This study aimed (i) to understand the effect of the alkali treatment onto kaolinites in order to improve their reactivity along alkaline activated materials, and finally to (ii) determine the role of crystal chemistry relative to their reactivities toward alkali activation. Thus, it has been shown that the degree of dissolution of kaolinites (82% of Al released for KGa-2 compare to 75% for KGa-1b in the case of NaOH treatment), is directly related to the type of alkaline treatment and the cation involved. Indeed, the quantity of Si and Al released is relative to the order: KOH<NaOH + KOH<NaOH. This difference can be directly explained by the different charge density between these two cations K + or Na + : the high charge density cation, such as Na + , induced more dissociation of hydroxyl groups compare to the low charge density cation one (K + ). However, the dissolution rate is higher in the poorly crystallized kaolinites, thus confirming the role of the crystallinity of the samples towards reactivity in an alkaline media. On the other hand, thermodynamic conditions cause zeolite-like precipitation in the case of an alkaline treatment based on NaOH. The dissolution process could thus be considered according to two steps: (i) a first rather short incongruent dissolution corresponding to the activation/dissolution of the octahedral layer by deprotonation (Al being link together to bonding oxygens with Si and to OH groups); (ii) a following congruent dissolution as soon as the system is initiated. This dissolution is accompanied by a change in the speciation of the aluminum probably on the edges of the particles from 6-coordinated to a 4-coordinated one, as shown by XAS and MAS-NMR results.

However, the dissolution process at the particle level is different depending on the type of cation used. Indeed, in the case of KOH, the dissolution is homogeneous, starting with the edges and surfaces, whereas in the case of NaOH, the dissolution is probably oriented thanks to areas of less coherence.

These new and unique results are essential to better understand the dissolution processes during the first steps of geopolymerization processes but also to better manage the type and reactivity of aluminosilicate alkaline sources and the choice of the cation of the alkaline solution. An offset was applied along the y-axis to all XANES curves for clarity. An offset was applied along the y-axis to all XANES curves for clarity.

  . Data were corrected for self-absorption based on the theoretical chemical formula of the mineral phases contained in the samples. References used for (i) Al K-edge XANES were synthetic gibbsite (Al(OH)3), synthetic kaolinite, boehmite (γ-AlO(OH)), orthoclase and andalusite (Figure SI 1 supplementary information), and for (ii) Si K-edge XANES, quartz, kaolinite, orthoclase, andalusite and halloysite (Figure SI 1 supplementary information). Solid-state NMR experiments were performed on a Bruker AVANCE III 700 spectrometer at 16.4 T (ν0( 27 Al) = 182.47 MHz) with 2.5 mm (25 kHz) double resonance Bruker MAS probes and with samples spun at the magic angle using ZrO2 rotors. For quantitative purposes, all 1D

  Al sites: δiso( 27 Al), CQ( 27 Al), ηQ( 27 Al), d(CSA) corresponding to full Width at Half Maximum of the isotropic chemical shift gaussian distribution. The morphology of samples was observed (a) by Scanning Electron Microscope (SEM) on a JEOL IT300 LV operating at 10kV, samples being previously carbon coated, and (b) by

Figure 1

 1 Figure 1 presents the evolution of Al and Si released during the dissolution of KGa-1b and KGa-2 kaolinites with 2M alkali solutions at 80°C along time. The kinetic of dissolution of kaolinites exhibits gradual release of [Al] and [Si] in solution whatever the type of kaolinites used until 12h with 2M of KOH or KOH + NaOH, and following a log function as a function of time (t < 12h)

Figure 1 .

 1 Figure 1. Proportion of Al (left) and Si (right) released (in mmol/kg of initial kaolinite) from kaolinites KGa-1b (upper diagrams) and KGa-2 (bottom diagrams) after various 2M alkali treatment along time (1, 3, 6, 12 and 24h). Circle, triangle and square refer to alkali treatments as KOH, NaOH and KOH + NaOH mixture, respectively. The dash line corresponds to the beginning of precipitation (6h).

Figure 2 .

 2 Figure 2. X-ray diffraction patterns of KGa-1b (a) and KGa-2 (b) after 24h of 2 M alkali

Figure 3 .Figure 4 .

 34 Figure 3. FTIR spectra of KGa-1b (a, b) and KGa-2 (c, d) after 24h of 2M alkali treatment (KOH, NaOH and KOH + NaOH mixture). Curves have been translated for the sake of clarity.

Figure 5 .

 5 Figure 5. XANES and first derivatives spectra at the Si K-edge of KGa-1b (top) and KGa-2

Figure 6 .

 6 Figure 6. 27 Al MAS NMR spectra of KGa-1b (top) and KGa-2 (bottom) samples after 24h of

Figure 7 .

 7 Figure 7. Example of 27 Al MQMAS spectrum of KGa-1b after 24h of NaOH treatment (left),

Figure 8 .

 8 Figure 8. TEM images of KGa-1b (left column) and KGa-2 (right column) samples before (a,

Figure 9 .

 9 Figure 9. Evolution of the number of Al and Si atoms per half kaolinite unit-cell from EDX

Acknowledgments

The authors thanks Project INIFUGE supported by Andra under the "Investing in the Future Programme" ("Investissement d'Avenir") -Selected under the Andra Call for Projects: "optimisation of post-dismantling radioactive waste management", organized in cooperation with the French National Research Agency (ANR). Moreover, we acknowledge SOLEIL for provision of synchrotron radiation facilities along project 20180745 and we would like to thank all the members for assistance in using LUCIA beamline, and the French Reg íon Ile de France SESAME program for financial support (700 MHz spectrometer). Finally, the authors thanks B.

Terasawa for Cobra, the saturday night fever and 80'ies music for nocturne beamline works.


The problem addressed in this paper is the automatic segmentation of stroke lesions on MR multisequences. Lesions enhance differently depending on the MR modality and there is an obvious gain in trying to account for various sources of information in a single procedure. To this aim, we propose a multimodal Markov random field model which includes all MR modalities simultaneously. The results of the multimodal method proposed are compared with those obtained with a mono-dimensional segmentation applied on each MRI sequence separately. We constructed an Atlas of blood supply territories to help clinicians in the determination of stroke subtypes and potential functional deficit.

I. INTRODUCTION

troke is a major cause of death and disability in both the more developed and the less developed world [START_REF] Fiez | Lesion Segmentation and Manual Warping to a Reference Brain: Intra-and Interobserver Reliability[END_REF] [START_REF] Sudlow | Comparable studies of the incidence of stroke and its pathological types. Results from an international collaboration[END_REF]. Stroke consumes an important part of the total healthcare costs (i.e. excluding social care and indirect costs) in Europe and the USA [START_REF] Evers | Economic evaluation in stroke research[END_REF]. Stroke is a vernacular term that denotes the sudden development of a neurological deficit. The overwhelming majority of strokes can be placed into two categories: haemorrhage (10% to 15%) and ischemia (approximately 85%), we consider here only the former [START_REF] David | Magnetic Resonance Imaging[END_REF].

Ischemia is a physiological term indicating insufficient blood flow for normal cellular function. Cerebral ischemia occurs when blood flow to the brain is reduced in either a global or a focal fashion.

Magnetic resonance imaging (MRI) offers unique advantages for the evaluation of cerebral ischemia, which leads to alterations in the brain water content, even in its earliest stages. Because of MRI's inherent sensitivity to depict alterations in tissue-free water content, it can detect ischemic insult to the brain within 1 hour after onset (with a diffusion sequence) [START_REF] David | Magnetic Resonance Imaging[END_REF].

The standard questions that must be answered when imaging a patient with stroke by any method are: Is there another lesion mimicking stroke? Is there a haemorrhagic or ischemic stroke? Are there any clues as to the cause of the ischemic stroke? What is the volume of stroke? How old is the stroke? Is salvageable tissue present? [START_REF] Hoggard | The Imaging of Ischaemic Stroke[END_REF].

In evaluating therapies for ischemic stroke patients, many physicians are interested in finding consistent, reliable estimates of lesion volume from MR images [START_REF] Stem | Statistical and Deformable Model Approaches to the Segmentation of MR Imagery and Volume Estimation of Stroke Lesions[END_REF]. The Manuscript received April 02, 2007. Y.Kabir, M.Dojat and B.Scherrer are with INSERM U836-UJF-CEA-CHU (Grenoble Institute of Neuroscience). (e-mail: yacine.kabir@imag.fr, michel.dojat@ujf-grenoble.fr, benoit.scherrer@imag.fr) C.Garbay is with LIG CNRS UMR 5217 (MAGMA) (e-mail: Catherine.Garbay@imag.fr) F.Forbes is with INRIA-Laboratory, Jean Kuntzman, Grenoble University (e-mail: Florence.Forbes@inrialpes.fr) traditional way for assessing stroke lesions is based on a manual segmentation. It consists of a manual tracing of the stroke regions on all contiguous slices in which the lesion was judged to be present. This manual segmentation is both time consuming and subject to manual variation. Another disadvantage of these interventions is their reliance upon subjective judgments, which raises the possibility that different observers will reach different conclusions about the presence or absence of lesions, or even that the same observer will reach different conclusions on different occasions [START_REF] Fiez | Lesion Segmentation and Manual Warping to a Reference Brain: Intra-and Interobserver Reliability[END_REF]. A computer automated algorithm to evaluate MRI stroke images as they are obtained may have therefore great clinical usefulness.

MRI Multimodal image segmentation attempts to take advantage of the different kinds of anatomical information provided by different imaging modalities. There are two major difficulties in performing multimodal image segmentation. First, multimodal data are not always available. Second, when the data are available, the various images are typically not in the same alignment, and therefore require registration.

II. RELATED WORK

A. Stroke lesion description

Ischemic stroke lesions in MR imaging are difficult to segment for various reasons, which include especially shape complexity and ambiguity. Creating and evaluating automatic methods for segmenting such lesions is difficult because ground-truth is elusive and stroke lesions are widely varied. In addition, accurate segmentation of stroke lesions requires anatomical knowledge. In particular changes in MR images due to ischemic stroke follow the vascular territory of the occluded blood vessel, which is characteristic of cerebrovascular disease and helps in differentiating it from other disease entities.

As a matter of fact, in the literature devoted to the segmentation of brain lesions, there has been few work done in the area of multimodal stroke segmentation [START_REF] Weinman | Nonlinear diffusion scale-space and fast marching level sets for segmentation of MR imagery and volume estimation of stroke lesions[END_REF].

Most of the work related concentrated on the detection of tumors [START_REF] Prastawa | A brain tumor segmentation framework based on outlier detection[END_REF][2] and multiple sclerosis lesions [START_REF] Leemput | Automated Segmentation of Multiple Sclerosis Lesions by Model Outlier Detection[END_REF].

III. METHOD

A. Patients and MRI data acquisition

Our input is a series of slices taken from different MR modalities of the same individual for 3 time points

B. Registration

A coregistration operation by affine transformation was used to correct the misalignment and mismatch among the different imaging modalities caused by patient movement or other factors [START_REF] Collignon | Automated multi-modality image registration based on information theory[END_REF], we consider the T2 sequence of session 1 as a reference image for all other sequences of all sessions.

C. Segmentation

Before performing the segmentation, the skull is removed from the images to keep brain tissues only [START_REF] Smith | Fast robust automated brain extraction[END_REF].

We consider a finite set of N voxels V = {1,…,N} on a regular three dimensional (3D) grid. When considering m different sequences simultaneously, each voxel i, i ∈ {1, . . . , N}, is described by a m-D intensity vector y i = (y 1i , . . . , y mi ). Our aim is to assign each voxel i to one of K classes considering the observed grey level intensities y i at voxel i. Lesion voxels are assumed to be distinctly different from normal tissues and we consider K=4 corresponding to 4 classes, namely, White Matter (WM), Grey Matter (GM), Cerebro-Spinal Fluid (CSF) and the lesion. Similarly to [START_REF] Leemput | Automated Segmentation of Multiple Sclerosis Lesions by Model Outlier Detection[END_REF] for Multiple Sclerosis data, we consider Stroke lesions as an additional class. Both observed intensities and unknown classes are considered to be random field denoted respectively by Y={Y 1 ,…,Y N } and Z={Z 1 ,….,Z N }. Each random variable Z i takes its values in {e 1 ,….e K } where e k is a K-dimensional binary vector corresponding to class k. Only the k th component of this vector is non zero and is set to 1. In a traditional Markov model based segmentation framework, it is assumed that the conditional field Z given Y=y is a Markov random field, ie.

)) , ( exp( ) , (

Φ

- = Φ = - Φ y z H W y Y z p y (1)
where H(z|y,Φ) is an energy function depending on some parameters Φ =(Φ y ,Φ z ) and given by:

∑ ∈ Φ - Φ = Φ V i y i i z z y p z H y z H ) , ( log ) ( ) , ( (2)
This energy is a combination of two terms: the first term in (2) is a regularization term that accounts for spatial dependencies between voxels. Denoting by N(i) the neighbours of voxels i, we will consider a Potts model with external field

∑ ∑ ∈ ∈       - = Φ V i i N j j i t i t i z z z v z z H ) ( 2 ) ( β (3)
The second summation above tends to favour neighbours that are in the same class when parameter β is positive. This β accounts for the strength of spatial interaction. Other parameters are the v i 's that are K-dimensional vectors defining the so-called external field. In this case Φ z ={v 1 ,…, v N , β} . The v i 's can be related to a priori weights accounting for the relative importance of the K classes at site i. The introduction of these extra parameters in the standard Potts model enables us to integrate a priori knowledge on classes. The second term in ( 2) is a data driven term based on intensities. For MRI we generally consider a Gaussian probability density function for the observed intensities y i when the tissue class is

z i . It follows that p(y i | Z i =e k ,Φ y ) = g(y i |µ k ,Σ k ) with       - Σ - - Σ = Σ - ) ( ) ( 2
1 ( exp | | ) 2 ( 1 ) , y ( 1 2 / 1 2 / i k i j T k i k m k k y y g µ µ π µ (4)
Where µ j and Σ j are the mean vector and covariance matrix of the j-th Gaussian. It follows that Φ y = {|µ k ,Σ k , k=1…K}. Segmentation is then performed according to the Maximum A Posteriori principle (MAP) by maximizing over z the probability p(z|Y=y,Φ). This requires the evaluation of an intractable normalizing constant W y,Φ and the estimation of unknown parameters Φ. A standard approach is to use the ICM algorithm that alternates between parameter estimation and segmentation but results in biased estimates. EM-based algorithms and variants proposed by [START_REF] Forbes | EM procedures using mean field-like approximations for Markov model-based image segmentation[END_REF] can be rather considered. They are based on Mean-field like approximations which make the MRF models case tractable. In all these approaches, MRF estimation is performed globally throw the entire volume.

D. Digital Atlas of Brain Blood supply territories

We constructed a digital Atlas of the Blood supply territories of the brain (BST), derived from the 12 printed serial sections in the axial plan developed by Tatu et al. [START_REF] Tatu | Arterial territories of the human brain[END_REF]. The atlas fits the Talairach space, this 3D atlas is used to determine the stroke subtype.

IV. RESULTS

To assess the gain in considering multimodal data we compare the segmentations obtained with single sequences to that obtained with multiple sequences (Fig. 2). Single modality segmentations show as expected that some of the modalities are not or less informative in term of lesion detection and cannot therefore be considered alone. In addition, the modalities information varies with the session. The multimodal approach has the advantage to intrinsically take that into account and to provide satisfactory results in all cases. Further analysis is required. In particular we propose to use Blood Supply territories Atlas (Fig. 3) to further assess the performance of the approach.

We have normalized the segmented images obtained into Talairach space in order to superimpose them on the Atlas of flood supply territories, we can see clearly that the stroke lesion is located in the Middle cerebral artery (MCA), such information is very relevant in the functional deficit determination and medical prognostic (Fig. 4). In Figure 4, the lesion present in the three sessions h1, h2 and h3 is mainly located in the MCA territory. For acute stage and sub-early acute stage, h1 and h2 respectively, the lesion seems extended to the deep territory (MCA perforating branches). However, for h3, the lesion is restricted to the leptomeningeal branches of the MCA. This indicates that the infarct extension to the deep territory is due to a cytotoxic edema developed during acute stage. This is confirmed by the clinician after an attentive examination on the images ai, bi, ci in Figure 2. By combining all the available information, the multi-modal segmentation appears as a powerful tool to correctly delineate the lesion, assign it the relevant vascular territory and provide synthetic information to the clinician.

V. SUMMARY AND CONCLUSION

An automatic MRI segmentation of stroke lesions was proposed, the algorithm is based on the simultaneous use of different MRI sequences to get more efficiency on lesion assessment. Preliminary experiments show promising results. Further algorithm refinements are required to obtain high level of sensitivity and make our system clinically viable. The potential impact on health care is great and continued efforts are warranted. Future work will focus on the use of Blood Supply Territories Atlas as a priori information in the segmentation process, in fact, a stroke lesion is restricted to a specific blood territory, this anatomical information can therefore be used to constraint the segmentation process to be restricted to a specific territory. The time dimension should be introduced in the algorithm by using the whole session series simultaneously.

  (3 sessions) (fig.1). 56 patients referred to our institution (Neurology Department of Grenoble Hospital) for suspected Multimodal MRI segmentation of ischemic stroke lesions Y.Kabir, M.Dojat, B.Scherrer, F.Forbes, C.Garbay S acute stroke. All examinations were performed on the same 1.5-T imaging device (Philips) . The MRI parameters were as follows: (1) axial T2FFE: TR/TE: 4096.87 ms/105.0 ms; Voxel size: 0.9375 × 0.9375 × 5; Flip angle: 15° (2) axial DW: TR/TE: 4599ms / 101 ms; Voxel size: 0.9375 × 0.9375 × 5; Flip angle: 90° (3) axial FLAIR: TR/TE, 10000 ms/140 ms; 0.9375 × 0.9375 × 5; Flip angle: 90°.

Fig 1 .

 1 Fig 1. Time points acquisition corresponding to 3 MRI sessions

Fig. 2 .

 2 Fig.2. MRI sequences with a stroke lesion in the middle cerebral artery territory (MCA) (ai) T2 sequence, (bi) Flair sequence, (ci) Diffusion sequence for the session i, (di),(ei) (fi) Segmentation of each sequence separately, (gi) Multimodal segmentation for session i i=1, 2, 3 correspond to sessions e1, e2, e3 respectively


Sylvain Charbonnier
email: sylvain.charbonnier@mnhn.fr

Denis Audo
email: denis.audo@edu.mnhn.fr

Alessandro Garassino
email: alegarassino@gmail.com

Martin Simpson
email: martinsimpsoniow@hotmail.com

Raymond Gèze

Dany Azar
email: danyazar@ul.edu.lb

Raymond Geze
email: rgeze@ul.edu.lb

A new species of mecochirid lobster, Meyeria libanotica (Decapoda, Glypheoidea), from the Barremian (Early Cretaceous) of Lebanon

Keywords: Crustacea, Malacostraca, Glypheidea, Mecochiridae, Neocomian, Sandstone of respectivement de Crustacea, Malacostraca, Glypheidea, Mecochiridae, Néocomien, Grès du Liban

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Lebanon, Shouf Sandstone Formation, Lebanon.

RÉSUMÉ

Un riche échantillon de langoustes mécochiridées (Crustacea, Decapoda, Mecochiridae) a été récemment récolté dans le Barrémien inférieur (Crétacé inférieur) du Liban. Les spécimens étudiés sont attribués à Meyeria libanotica sp. nov. Le genre Meyeria M'Coy, 1849 est aussi révisé et de nouvelles combinaisons sont proposées pour deux espèces : Meyeria bartholomaii (Jell, Woods et Cook, 2017) comb. nov. (Aptien, Australie), et Meyeria rostrata (Collins et Rasmussen, 1992) comb. nov. (Campanien-Maastrichtien, Groenland). La répartition stratigraphique et la distribution paléogéographique de Meyeria s'étendent maintenant

Introduction

Palaeontologically, Lebanon is known for its numerous Lower Cretaceous amber outcrops and its famous Upper Cretaceous fossil Konservat-Lagerstätten (e.g., Cenomanian: Hjoula, Haqel, and En-Nammoura; Santonian: Sahel Aalma). Indeed, for the Cenomanian localities, the sub-lithographic limestones yield varied and exquisitely preserved fossils including vertebrates (fish, reptiles), invertebrates (arthropods, annelids, cephalopods, echinoderms) and terrestrial plants. Amongst the arthropods, malacostracans are the most common fossils and they were the subject of several studies [START_REF] Brocchi | Note sur une nouvelle espèce de crustacé fossile (Penaeus libanensis)[END_REF][START_REF] Fraas | Geologisches aus dem Libanon[END_REF][START_REF] Dames | Ueber einige Crustaceen aus den Kreideablagerungen des Libanon[END_REF][START_REF] Glaessner | Cretaceous Crustacea from Mount Lebanon, Syria[END_REF][START_REF] Roger | Invertébrés des couches à poissons du Crétacé supérieur du Liban[END_REF][START_REF] Förster | Bärenkrebse (Crustacea, Decapoda) aus dem Cenoman des Libanon und dem Eozän Italiens[END_REF][START_REF] Garassino | The macruran decapod crustaceans of the Upper Cretaceous of Lebanon. Paleontologia Lombarda Nuova serie[END_REF][START_REF] Garassino | New decapod crustaceans from the Cenomanian (Upper Cretaceous) of Lebanon[END_REF][START_REF] Larghi | Brachyuran Decapod Crustacea from the Upper Cretaceous of Lebanon[END_REF][START_REF] Garassino | Cretasergestes sahelalmaensis n. gen., n. sp. (Crustacea, Decapoda, Sergestidae) and Cancrinos libanensis n. sp. (Crustacea, Decapoda, Palinuridae) from the Late Cretaceous (Cenomanian) of Lebanon[END_REF][START_REF] Schram | Thylacocephala (Arthropoda: Crustacea?) from the Cretaceous of Lebanon and implications for thylacocephalan systematics[END_REF]Audo andCharbonnier, 2012, 2013;[START_REF] Petit | Fossil sponge gemmules, epibionts of Carpopenaeus garassinoi n. sp. (Crustacea, Decapoda) from the Sahel Alma Lagerstätte (Late Cretaceous, Lebanon)[END_REF]Charbonnier et al., 2017aCharbonnier et al., , 2017b;;[START_REF] Garassino | A new fury lobster (Crustacea, Decapoda, Synaxidae) from the Upper Cretaceous (Cenomanian) of Lebanon[END_REF][START_REF] Pasini | A new ghost shrimp (Axiidea, Callianopsidae) from the Late Cretaceous (Cenomanian) of Hadjoula, Lebanon[END_REF].

Recently, a new sample of decapod crustaceans, preserved in calcareous nodules, has been collected by the co-authors R. Gèze and D. Azar, from the Lower Cretaceous (lower Barremian) of three localities (Fig. 1): one in Bqaatouta, and two localities in Mazraat Kfardibiane, all in Caza (District) Kesserouan, Mouhafazit Jabal Loubnan (Governorate Mont Liban). This discovery constitutes a novelty in the fossil record of Lebanon. The main aim of this study is to describe for the first time these Barremian crustaceans occurring in the "Grès du Liban" also named "Grès de base" or Shouf Sandstone Formation in Lebanon. This description is accompanied by a revision of Meyeria M'Coy, 1849.

Geological setting

The Cretaceous succession of Lebanon was described and dated mainly by [START_REF] Dubertret | Révision de la stratigraphie du Crétacé du Liban[END_REF], [START_REF] Dubertret | Carte géologique du Liban au 1/200 000 e . République Libanaise[END_REF][START_REF] Saint-Marc | Étude stratigraphique et micropaléontologique de l'Albien, du Cénomanien et du Turonien du Liban[END_REF]. It has been admitted for a long time that the lowest unit of the Cretaceous is the prominent sandstone unit traditionally known as the "Grès de Base" or "C1" as termed in the geological maps of Lebanon. The classical proposed age of this division was agreed to be Neocomian, although [START_REF] Walley | The Lithostratigraphy of Lebanon: A Review[END_REF] considered that the age range of this formation is problematic: in theory it could extend anywhere from terminal Tithonian to early Aptian, a time period that is around twenty million years [START_REF] Gradstein | A Phanerozoic time scale[END_REF]. However, by analogy with the much better known sequence to the south and in Mount Hermon (i.e. [START_REF] Shimron | Cretaceous magmatism along the southeastern flanks of Mount Hermon[END_REF], it is likely there was a low deposition rate during Berriasian and Valanginian time, and the basal beds were probably deposited as late as Hauterivian or even early Barremian age. This unit was formalized by [START_REF] Walley | A revision of the Lower Cretaceous stratigraphy of Lebanon[END_REF] as the "Shouf Sandstone Formation", who considered it as one of the most distinctive units in Lebanon [START_REF] Walley | The Lithostratigraphy of Lebanon: A Review[END_REF]. Recent stratigraphical and palaeontological studies attributed an early Barremian age for this unit based on benthic foraminifera [START_REF] Granier | New fossiliferous sites with Barremian Charophyta in the "Grès du Liban" auct. (Lebanon), with a critical perspective regarding the nature of Munieria Deecke, 1883[END_REF][START_REF] Granier | Some steps toward a new story for the Jurassic-Cretaceous transition in Mount Lebanon[END_REF][START_REF] Maksoud | New data on the age of the Lower Cretaceous amber outcrops of Lebanon[END_REF].

The "Grès du Liban" also named "Grès de base" or Shouf Sandstone Formation consists mostly of ferruginous, brown to white sandstone with associated clay, shale and lignite. Some of the darker layers contain woody or coaly fragments, often including pyrite and amber [START_REF] Walley | The Lithostratigraphy of Lebanon: A Review[END_REF][START_REF] Maksoud | Lebanese amber: latest updates[END_REF]. Locally, the "Grès du Liban" contains basaltic volcanics and reddish clayey beds, which appear to be weathered volcanic tuff. The "Grès du Liban" is very variable in thickness, ranging from a few meters to 300 m thick. It is presumed to be largely fluvial to deltaic and littoral in origin. The general trend is that the sequence passes from fluvial at the base and in the east to deltaic at the top and in the west.

Material and methods

The fossil decapods were collected from two localities (Fig. 1): Bqaatouta with one outcrop (El-Rouaisseh, 33° 58.383' N; 35°47.005' E; Fig. 2A), and Mazraat Kfardibiane with two outcrops separated from each other by about 300 m: Es-Sohoum (33° 59.270' N; 35° 47.421' E; Fig. 2B) and in the valley, Haqlet Es-Saiyed (33° 59.301' N; 35°47.606' E; Fig. 2C). All outcrops are in Caza (District) Kesserouan, Governorate Mount-Lebanon, Central Lebanon.

The studied sample includes 90 specimens of mecochirid lobsters. All studied specimens are preserved three-dimensionally, slightly compressed, and partially exposed on the surface of subnodular, irregular ferruginous limonite concretions. They are rarely articulated, occurring mostly as incomplete parts. The epicuticle generally is poorly preserved. Sometimes the parts of the body correspond only to inner casts. For higher-level classification, we follow [START_REF] Charbonnier | A worldwide review of fossil and extant glypheid and litogastrid lobsters (Crustacea, Decapoda, Glypheoidea)[END_REF] and [START_REF] Charbonnier | Phylogeny of fossil and extant glypheid and litogastrid lobsters (Crustacea, Decapoda) as revealed by morphological characters[END_REF]. Feldmann et al. (2015: 23). "Subcylindrical carapace with deep cervical groove extending into the antennal groove; strongly backward and parallel postcervical and branchiocardiac grooves and weak hepatic groove; three tuberculate carinae in the gastric region; dorsal margin of carapace denticulate in the anterior one-third; short rostrum lacking supra-and subrostral teeth; strongly elongate pereiopod 1 mostly pseudochelate; pereiopod 2 shorter than first, mostly pseudochelate; pereiopods 3-5 with terminal dactylus; subrectangular pleonal somites; subrectangular telson; exopodite with diaeresis."

Diagnosis by

Emended diagnosis (present work). Subcylindrical carapace, laterally compressed,

with ogival-shaped cross-section; pointed rostrum; antennal-pterygostomial region with strongly concave ventral margin; cervical groove strongly oblique, ventrally joined to antennal groove, delimiting narrow cephalic region; cephalic region with generally three longitudinal carinae; postcervical and branchiocardiac grooves parallel, straight, directed toward posterior margin; postcervical groove joined ventrally to branchiocardiac groove, forming one elongate lobe; elongate and wide cardiac groove, forward-inclined, joined to postcervical groove and to dorsal margin; deep hepatic groove, curved toward posterior; short inferior groove, joined to hepatic groove and interrupted before reaching ventral margin; pleon about twice the length of carapace; subrectangular telson; pseudochelate P1, strongly elongate; P2 shorter than first; pseudochelate P3-P5 with terminal dactylus. [START_REF] Garassino | Jabaloya aragonensis n. gen., n. sp. (Crustacea, Decapoda, Mecochiridae) and Cedrillosia jurassica n. gen., n. sp. (Crustacea, Decapoda, Glypheidae) from the Upper Jurassic of Teruel Province (Aragón, Spain)[END_REF] from the Oxfordian of Spain (see review in [START_REF] Robin | Bivalves on mecochirid lobsters from the Aptian of the Isle of Wight: Snapshot on an Early Cretaceous palaeosymbiosis[END_REF]. -Meyeria bartholomaii [START_REF] Jell | Mecochirus Germar (Decapoda: Glypheoidea) in the Lower Cretaceous of Queensland[END_REF] [START_REF] Van Straelen | Crustacés décapodes nouveaux ou peu connus de l'époque Crétacique[END_REF] from the Albian of France (see review in [START_REF] Breton | Mecochiridae (Crustacea, Decapoda, Glypheidea) de l'Albien et du Cénomanien de France[END_REF]. -Meyeria libanotica sp. nov. from the Barremian of Lebanon (this work). -Meyeria ornata (M'Coy, 1849) from the Hauterivian of United Kingdom, France, Germany, The Netherlands, and Switzerland, and from the Aptian of United Kingdom (see [START_REF] Simpson | Gross morphology and the mode of life of two species of lobster from the Early Cretaceous of England: Meyeria ornata (Phillips) and Meyerella magna (M'Coy)[END_REF]. -Meyeria rostrata [START_REF] Collins | Upper Cretaceous-Lower Tertiary decapod crustaceans from West Greenland[END_REF] comb. nov. from the late Campanian and Maastrichtian of West Greenland. -Meyeria serratosae (Dupuy de Lôme and de la Revilla, 1956) from the Jurassic of Spain (see review in [START_REF] Charbonnier | A worldwide review of fossil and extant glypheid and litogastrid lobsters (Crustacea, Decapoda, Glypheoidea)[END_REF]. [START_REF] Woodward | Further notes on podophthalmous crustaceans from the Upper Cretaceous formation of British Columbia[END_REF] from the Late Cretaceous of British Columbia, Canada has not been considered because the description is very scant with no figure [START_REF] Woodward | Further notes on podophthalmous crustaceans from the Upper Cretaceous formation of British Columbia[END_REF]. Moreover, [START_REF] Feldmann | A new species of Meyeria (Decapoda: Mecochiridae) from the San Juan Raya Formation (Aptian: Cretaceous), Puebla state, Mexico[END_REF] reported that the holotype has been lost. Agreeing with [START_REF] Förster | Die Mecochiridae, eine spezialisierte Familie der mesozoischen Glypheoidea (Crustacea, Decapoda)[END_REF] and [START_REF] Feldmann | A new species of Meyeria (Decapoda: Mecochiridae) from the San Juan Raya Formation (Aptian: Cretaceous), Puebla state, Mexico[END_REF], we consider this species as a nomen dubium.

Included fossil species. Meyeria aragonensis

Remarks. Meyeria? harveyi

Recently, [START_REF] Jell | Mecochirus Germar (Decapoda: Glypheoidea) in the Lower Cretaceous of Queensland[END_REF] described Mecochirus bartholomaii from the Aptian of Queensland, Australia. Careful examination of the figures provided by the authors lead us to identify morphological characters, which are diagnostic of Meyeria, especially the elongate and wide cardiac groove joined to the dorsal margin, and the short inferior groove, interrupted before reaching the ventral margin. This carapace groove pattern is typical of Meyeria. Hence, the new combination Meyeria bartholomaii [START_REF] Jell | Mecochirus Germar (Decapoda: Glypheoidea) in the Lower Cretaceous of Queensland[END_REF]) is here proposed. [START_REF] Collins | Upper Cretaceous-Lower Tertiary decapod crustaceans from West Greenland[END_REF] described Mecochirus rostratus from the late Campanian and Maastrichtian of West Greenland. Careful examination of the dorsal view of the paratype figured by Collins and Rasmussen (1992: fig. 3b) lead us to identify morphological characters, which are diagnostic of Meyeria. Indeed, the paratype shows the elongate and wide cardiac groove, which is also clearly described in the text ("a faint groove passes upward from the postcervical furrow to the dorsal margin") but not recognized or named as such.

Thus, the new combination Meyeria rostrata [START_REF] Collins | Upper Cretaceous-Lower Tertiary decapod crustaceans from West Greenland[END_REF]) is here proposed. Pleonal appendages. Uropods poorly preserved, connected to smooth basipodite; each with median longitudinal carina; uropodal exopod with serrate outer margin, and straight diaraesis; uropodal endopod with fibrous, flexible distal portion.

Meyeria libanotica

Discussion. The new species shows a carapace groove pattern diagnostic of Meyeria, especially the elongate and wide cardiac groove joined to the dorsal margin, the subcircular hepatic groove, and the short inferior groove. Meyeria libanotica sp. nov. differs from all other species of Meyeria by its strong hepatic carina (absent in all other species). Meyeria libanotica differs from M. ornata, M. rostrata, and M. bartholomaii by its short, unarmed rostrum (vs spiny in M. ornata, elongate and spiny in M. bartholomaii and M. rostrata).

Meyeria libanotica differs from M. aragonensis by its three longitudinal cephalic carinae (vs only one cephalic carina in M. aragonensis). Meyeria libanotica sp. nov. differs from many other species of Meyeria by its smooth cardiac, gastric, and cephalic regions (vs covered by small or strong tubercles in M. aragonensis, M. gracilis, M. houdardi, M. ornata, and M. serratosae; with scattered tubercles in M. bartholomaii and M. crofti).

The hepatic carina observed in Meyeria libanotica sp. nov. is reminiscent of that observed in Atherfieldastacus Simpson in [START_REF] Robin | Bivalves on mecochirid lobsters from the Aptian of the Isle of Wight: Snapshot on an Early Cretaceous palaeosymbiosis[END_REF] does not extend posteriorly into ventral branchial ridge (ridge "r1" of [START_REF] González-León | Morphology and ontogeny of the fossil lobster Meyeria magna M'Coy, 1849 (Astacidae, Mecochiridae) from the Lower Cretaceous (Lower Aptian) of Mexico, United Kingdom and Spain[END_REF]. Similarly, the subrectangular telson with median groove and proximal axial pair of tubercles of M. libanotica sp. nov. is also observed in Atherfieldastacus magnus (M' Coy, 1849) as well as in Mecochirus longimanatus [START_REF] Schlotheim | Die Petrefactenkunde auf ihrem jetzigen Standpunkte durch die Beschreibung seiner Sammlung versteinerter und fossiler Uberreste des Thier-und Pflanzenreichs der Vorwelt erlautert[END_REF] regarding the subrectangular shape of the telson. Associated with the very elongate, slender P1 pereiopods, these morphological characters add to the definition of the family Mecochiridae.

Conclusion

Meyeria libanotica sp. nov. is the first occurrence of the genus in the Barremian.

Taking into account the present review, Meyeria M'Coy, 1849 includes nine species. Thus, the stratigraphic range and palaeogeographic distribution of the genus spread from the Oxfordian (Late Jurassic) to the Maastrichtian (Late Cretaceous) and from Australia to Greenland, through Europe, respectively. Thorough research is now required to better understand the Cretaceous diversification and biogeographic distribution of mecochirid lobsters. Charbonnier.

Fig

  Institutional abbreviations: MHN.UL, Muséum d'Histoire Naturelle de l'Université Libanaise, Faculté de Sciences II, Fanar, Lebanon ; MNHN.F, collection de Paléontologie, Muséum national d'Histoire naturelle, Paris, France ; MIM, Mineral Museum, Beirut, Lebanon.Anatomical abbreviations: CL, carapace length, exclusive of rostrum; CH, carapace height; P1-P5, pereiopods 1 to 5; s1-s6, pleonal somites 1 to 6.Paper registration: urn:lsid:zoobank.org:pub:1C71FB9B-6588-4C80-Astacus ornatus Phillips, 1829, original designation by M'Coy (1849: 333).

  comb. nov. from the Aptian of Queensland, Australia. -Meyeria crofti Ball, 1960 from the Campanian of James Ross Island, Antarctic. -Meyeria gracilis Glaessner, 1932 from the Hauterivian of Germany. -Meyeria houdardi

  Figs 3-6Etymology. The specific epithet refers to Lebanon (Middle East) where the species was collected.

Fig. 6 .

 6 Fig. 6. Meyeria libanotica sp. nov. from the Barremian of Central Lebanon. A-B, paratype MHN.UL.P.25439/5V from Haqlet Es-Saiyed, subcomplete specimen with carapace connected to pleon, right lateral view (A) and interpretative line drawing (B). C-D, paratype MHN.UL.P25451/7 from El-Rouaisseh, limonitized specimen with complete pleon, left lateral (C) and right lateral (D) views. Abbreviations: bap, uropodal basipodite; ct, carapace; di, diaeresis; ex, uropodal exopod; en, uropodal endopod; P1-P5, pereiopods 1 to 5; s1-s6, pleonal somites 1 to 6; t, telson; vm, ventral margin. Scale bars: 10 mm. Photographs: C. Lemzaouda (A, C, E, I), L. Cazes (F-H). Line drawing: S. Charbonnier. Meyeria libanotica sp. nov. du Barrémien du Liban central. A-B, paratype

  . 1. Geological map of the area of study in Caza Kesserouan, Governorate Mount-Lebanon, Central Lebanon (adapted from[START_REF] Dubertret | Carte géologique au 50 000 e , Feuille de Zahlé[END_REF]. The localities yielding specimens of Meyeria libanotica sp. nov. are Bqaatouta with El-Rouaisseh outcrop and Mazraat Kfardibiane with Es-Sohoum and Haqlet Es-Saiyed outcrops. Meyeria libanotica sp. nov. from the Barremian of Central Lebanon. Note the carapace was whitened with ammonium chloride sublimate (C) to highlight the groove pattern. E-H, paratype MHNN.F.A42018 (Gèze coll.) from El-Rouaisseh, carapace and pereiopods, left lateral (E) and right lateral (F) views, interpretative line drawings (G, H). Abbreviations: a, branchiocardiac groove; Meyeria libanotica sp. nov. from the Barremian of Haqlet Es-Saiyed, Central Lebanon.

	groove. E-F, paratype MHNN.F.A72019 (Gèze coll.) from El-Rouaisseh, carapace and
	pereiopods, left lateral view and interpretative line drawing. G-I, paratype A-E, paratype MHN.UL.P.25439/3V, subcomplete specimen in right lateral view (A),
	MHN.UL.P.25439/2V from Haqlet Es-Saiyed, subcomplete specimen with carapace, pleon interpretative line drawing of carapace (B), detail of pleon and tail fan (C) and
	Carte géologique de la zone d'étude dans le District de Kesserouan, Gouvernorat du Mont-Liban, Liban central (adaptée d'après Dubertret, 1953). Les localités livrant des spécimens de Meyeria libanotica sp. nov. sont Bqaatouta avec l'affleurement d'El-Rouaisseh et Mazraat Kfardibiane avec les affleurements d'Es-Sohoum et de Haqlet Es-Saiyed. Affleurement de Mazraat Kfardibiane (Es-Sohoum, 33° 59.270' N; 35° 47.421' E). C, Affleurement de la vallée de Mazraat Kfardibiane (Haqlet Es-Saiyed, 33° 59.301' N; 35°47.606' E). Le géologue, qui donne l'échelle sur les photos, est le co-auteur R. Gèze. Photographies : D. Azar. postcervical groove; cd, cardiac groove; ct, carapace; dm, dorsal margin; e1e, cervical P1-P5, pereiopods 1 to 5; s1-s2, pleonal somites 1 to 2; vm, ventral margin. Scale bars: 10 mm. Photographs: L. Cazes (A-C), C. Lemzaouda (E, F). Line drawings: S. Charbonnier. carène orbitaire ; P1-P5, péréiopodes 1 à 5 ; s1-s2, somites pléonaux 1 à 2 ; vm, marge ventrale. Barres d'échelle : 10 mm. Photographies: L. Cazes (A-C), C. Lemzaouda (E, F). Dessins : S. Charbonnier. Fig. 4. Meyeria libanotica sp. nov. from the Barremian of Central Lebanon. A-D, paratype MHN.UL.P25451/6 from El-Rouaisseh, limonitized carapace in right lateral (A), left and fragments of pereiopods, right lateral (G) and left lateral (H) views, interpretative line drawing of carapace (I). Abbreviations: a, branchiocardiac groove; ac, antennal carina; an, groove; dm, dorsal margin; e1e, cervical groove; gc, gastro-orbital carina; hr, hepatic carina; i, inferior groove; me, merus; oc, orbital carina; on, orbital notch; P1-P5, pereiopods 1 to 5; vm, ventral margin. Scale bars: 10 mm. Photographs: L. Cazes (A-D), C. Lemzaouda (E, G, H). Line drawings: S. Charbonnier. Meyeria libanotica sp. nov. du Barrémien du Liban central. A-D, paratype MHN.UL.P25451/6 from El-Rouaisseh, carapace limonitisée en vues latérales droite (A) et gauche (B) et vues dorsales (C, D). Notez que la carapace a été blanchie au chlorure d'ammonium (D) pour mettre en évidence les sillons, notamment le long sillon cardiaque. E-F, paratype MHNN.F.A72019 (coll. Gèze) d'El-Rouaisseh, carapace et péréiopodes, vue latérale gauche et dessin interprétatif. G-I, paratype MHN.UL.P.25439/2V de Haqlet Es-Saiyed, subcomplete spécimen subcomplet avec carapace, pléon et fragments de péréiopodes, vues latérales droite (G) et gauche (H), dessin interprétatif de la carapace (I). Abréviations : a, sillon branchiocardiaque ; ac, carène antennaire ; an, encoche antennaire ; b, sillon antennaire ; b1, sillon hépatique ; c, sillon postcervical ; cd, sillon cardiaque ; dm, marge dorsale ; e1e, sillon cervical ; gc, carène gastro-orbitaire ; hr, carène hépatique ; i, sillon inférieur ; me, mérus ; oc, carène orbitaire ; on, encoche orbitaire ; P1-P5, péréiopodes 1 à 5 ; vm, marge ventrale. Barres d'échelle : 10 mm. interpretative line drawing (D), closed-up of dorsal surface of carapace showing the rostrum (E). F-H, paratype MHN.UL.P.25439/4V, carapace preserved in limonitized MHN.UL.P.25439/9V, isolated P1 propodus with strong distal spine on ventral margin and longitudinal rows of tubercles on outer surface, interpretative line drawing (J). MHN.UL.P.25439/4V, carapace préservée dans un nodule limonitisé, vues latérales droite (F) et gauche (G) et vue dorsale (H). I-J, paratype MHN.UL.P.25439/9V, propodus P1 isolé, muni d'une grosse épine distale sur la marge ventrale et de rangées longitudinales de tubercules sur la surface externe, dessin interprétatif (J). Abréviations : a, sillon épine distale ; s4-s6, somites pléonaux 4 à 6 ; t, telson ; vm, marge ventrale. Barres d'échelle : 10 mm. Photographies : C. Lemzaouda (A, C, E, I), L. Cazes (F-H). Dessins : S. Fig. 3. ac, antennal carina; an, antennal notch; b, antennal groove; b1, hepatic groove; c, groove; gc, gastro-orbital carina; hr, hepatic carina; i, inferior groove; oc, orbital carina; antennal notch; b, antennal groove; b1, hepatic groove; c, postcervical groove; cd, cardiac nodule, right lateral (F), left lateral (G) and dorsal (H) views. I-J, paratype Charbonnier.
	lateral (B) and dorsal (C, D) views. Note the carapace was whitened with ammonium
	chloride sublimate (D) to highlight the groove pattern, especially the elongate cardiac

Fig. 2. Studied localities in Caza Kesserouan, Governorate Mount-Lebanon, Central Lebanon A, Outcrop of Bqaatouta (El-Rouaisseh, 33° 58.383' N; 35°47.005'). B, Outcrop of Mazraat Kfardibiane (Es-Sohoum, 33° 59.270' N; 35° 47.421' E). C, Outcrop of Mazraat Kfardibiane valley (Haqlet Es-Saiyed, 33° 59.301' N; 35°47.606' E). The geologist shown in the images for scale is the co-author R. Gèze. Photographs: D. Azar. Localités étudiées dans le District de Kesserouan, Gouvernorat du Mont-Liban, Liban central. A, Affleurement de Bqaatouta

 33° 58.383' N; 35°47.005')

. B, A-D, holotype MHN.UL.P.25439/1V from Haqlet Es-Saiyed, carapace in left lateral (A), and dorsal (B, C) views, interpretative line drawing (D). Meyeria libanotica sp. nov. du Barrémien du Liban central. A-D, holotype MHN.UL.P.25439/1V de Haqlet Es-Saiyed, carapace en vue latérale gauche (A) et vues dorsales (B, C), dessin interprétatif (D). Notez que la carapace a été blanchie au chlorure d'ammonium (C) pour mettre en évidence les sillons. E-H, paratype MHNN.F.A42018 (coll. Gèze) d'El-Rouaisseh, carapace et péréiopodes, vues latérales gauche (E) et droite (F), dessins interprétatifs (G, H). Abréviations: a, sillon branchiocardiaque ; ac, carène antennaire ; an, encoche antennaire ; b, sillon antennaire ; b1, sillon hepatic ; c, sillon postcervical ; cd, sillon cardiaque ; ct, carapace ; dm, marge dorsale ; e1e, sillon cervical ; gc, carène gastro-orbitaire ; hr, carène hépatique ; i, sillon inférieur ; oc, Photographies: L. Cazes (A-D), C. Lemzaouda (E, G, H). Dessins : S. Charbonnier. Fig. 5. Abbreviations: a, branchiocardiac groove; ac, antennal carina; an, antennal notch; b, antennal groove; bap, uropodal basipodite; b1, hepatic groove; c, postcervical groove; cd, cardiac groove; dm, dorsal margin; ex, uropodal exopod; en, uropodal endopod; e1e, cervical groove; gc, gastro-orbital carina; hr, hepatic carina; i, inferior groove; me, merus; oc, orbital carina; on, orbital notch; r, rostrum; sp, distal spine; s4-s6, pleonal somites 4 to 6; t, telson; vm, ventral margin. Scale bars: 10 mm. Photographs: C. Lemzaouda (A, C, E, I), L. Cazes (F-H). Line drawings: S. Charbonnier. Meyeria libanotica sp. nov. du Barrémien de Haqlet Es-Saiyed, Liban central. A-E, paratype MHN.UL.P.25439/3V, spécimen subcomplet en vue latérale droite (A), dessin interprétatif de la carapace (B), pléon et éventail caudal (C) et dessin interprétatif (D), détail de la surface dorsale de la carapace montrant le rostre (E). F-H, paratype branchiocardiaque ; ac, carène antennaire ; an, encoche antennaire ; b, sillon antennaire ; bap, basipodite de l'uropode ; b1, sillon hépatique ; c, sillon postcervical ; cd, sillon cardiaque ; dm, marge dorsale ; ex, exopode de l'uropode ; en, endopode de l'uropode ; e1e, sillon cervical ; gc, carène gastro-orbitaire ; hr, carène hépatique ; i, sillon inférieur ; me, mérus ; oc, carène orbitaire ; on, encoche orbitaire ; r, rostre ; sp,

Acknowledgements

We are grateful to the reviewers Rodney M. Feldmann (Kent State University, USA) and Matúš Hyžný (Comenius University, Slovakia) for their constructive comments. We thank Christian Lemzaouda (now retired) and Lilian Cazes (UMR 7207 CR2P) for assistance in photographic work. This paper is a contribution to the activity of the laboratory "Advanced Micropalaeontology, Biodiversity and Evolution Researches" (AMBER) led by Dany Azar at the Lebanese University, Faculty of Sciences II (Department of Natural Sciences). Dany Azar wants to thank the Chinese Academy of Sciences for the support under the President's International Fellowship Initiative (PIFI).