# From Fe Li rich micas to lepidolite and muscovite: The magmatic to hydrothermal evolution of phyllosilicates in the apical zone of the Beauvoir granite (French Massif Central)

Zia Steven Kahou, Michel Cathelineau, Marie-Christine Boiron, Andreï Lecomte, Chantal Peiffert, Patrick Fullenwarth

► To cite this version:

Zia Steven Kahou, Michel Cathelineau, Marie-Christine Boiron, Andreï Lecomte, Chantal Peiffert, et al.. From Fe Li rich micas to lepidolite and muscovite: The magmatic to hydrothermal evolution of phyllosilicates in the apical zone of the Beauvoir granite (French Massif Central). Lithos, 2026, 524-525, pp.108418. 10.1016/j.lithos.2026.108418. hal-05484986

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From Fe-Li rich micas to lepidolite and muscovite: the magmatic to hydrothermal evolution of phyllosilicates in the apical zone of the Beauvoir granite

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Zia Steven Kahou¹, Michel Cathelineau¹*, Marie-Christine Boiron¹, Andreï Lecomte¹, Chantal

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Peiffert¹, Patrick Fullenwarth²

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Université de Lorraine, CNRS, GeoRessources, F-54000, Nancy, France

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Imerys Ceramics France – Kaolins de Beauvoir, Echassières 03330, France

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* Corresponding author: Michel Cathelineau, michel.cathelineau@univ-lorraine.fr

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Abstract

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The albite–lepidolite–topaz Beauvoir granite (western European Variscan belt) represents an extreme example of late-stage peraluminous magmatic differentiation associated with enrichment in Li, Sn, Nb, Ta and Be. This study investigates the textures and chemistry of micas from the highly evolved B1 unit to constrain the final stages of magmatic evolution and to evaluate the impact of post-magmatic fluid–rock interaction. Magmatic mica assemblages are dominated by lepidolite, whereas Fe–Li micas are rare and preserved only locally; both display high Li contents (28,000–32,000 ppm) and record late-stage Rb–Cs enrichment. Hydrothermal alteration is expressed by the development of fine-grained dioctahedral muscovite along fracture-controlled alteration corridors, where albite and lepidolite are progressively replaced. Hydrothermal muscovite is nearly Li-free (~90 ppm), and its formation leads to a pronounced decrease in the modal abundance of lepidolite (from ~20% to 5–10%), resulting in significant Li depletion at the whole-rock scale despite limited Li loss from residual lepidolite crystals. Muscovitisation is also associated with the depletion of Nb, Ta and W, whereas Sn is partly redistributed and incorporated into muscovite (up to 1,400 ppm). The absence of transitional compositions toward Li-rich muscovite or phengite indicates that this alteration stage is
decoupled from magmatic differentiation and reflects a structurally controlled hydrothermal
event. These results highlight the key role of post-magmatic hydrothermal processes in rare-
metal redistribution and in reducing the lithium endowment of highly fractionated granites.

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30 **Keywords:** Beauvoir rare-metal granite – Magmatic and hydrothermal stages – Lepidolite –
Muscovite – Lithium and rare metals – LA-ICP-MS
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## Introduction

The transition to renewable energy and electric mobility to limit global warming implies greater consumption of mineral resources, including lithium (Li). According to the International Energy Agency (IEA), Lithium demand for electric mobility alone is expected to increase 40-fold by 2050 (IEA, 2021). In other words, lithium is a strategic metal and a key to a zero-net-carbon world. More than half of lithium comes from hard-rock deposits (Australia (Greenbushes, 392,000 tons of spodumene concentrates in 2024)), China (Yichun, 82,000 tons of Li carbonate in 2021), Zimbabwe (22,000 t of Li), and a little production more for ceramics in Portugal (Covas do Barroso, 400 metric tons of Li in 2024)), and the rest comes from salar brines (Chile, Argentina, China, and the US). Hard-rock potential deposits include evolved pegmatites of Lithium-Caesium-Tantalum (LCT) subtypes (Černý and Ercit, 2005) and, to a lesser extent, peraluminous rare-metals granites (RMG) such as Argemela (Portugal), Yichun (China), and Beauvoir (France) granites (Breiter et al., 2023a; Cuney et al., 1992; Huang et al., 2002). Apart from albite and quartz, micas are the most abundant minerals in RMG and can be accompanied by Li-rich phosphates (e.g., amblygonite and montebrasite). Two types of Li-rich micas are generally distinguished in RMG: i) the polylithionite-zinnwaldite series and ii) the trilithionite-polylithionite (lepidolite) series, both describing the Li-Fe (siderophyllite-Li-rich annite) and Li-Al (zinnwaldite-lepidolite) series as described by Tischendorf et al. (1997). In addition, micas are the main Li-bearing minerals in RMG, sometimes followed by Li-phosphates. Due to their sheet-like structures (Foster, 1960; Tischendorf et al., 2001), micas may contain elements other than K in the interlayer, such as Rb and Cs (Cerny et al., 2003), and in the octahedral site, Al and Fe may be substituted for Li, Sn, W, Nb, and Ta (Brigatti et al., 2007; Breiter et al., 2023a, b, c). These characteristics make micas the main metal trap of the RMG, in addition to metal oxides (cassiterite, Nb-Ta oxides, microlite). Furthermore, the textural features, the metal content (especially Li), and the trace element composition of the

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micas are good markers of the magmatic to hydrothermal conditions that led to their formation and the alteration that affected them (Breiter et al., 2023b; Legros et al., 2016; Martins et al., 2012; Monier et al., 1987; Monnier et al., 2022; Roda-Robles et al., 2006, 2016; Van Lichtervelde et al., 2008; Vieira et al., 2011). In evolved granites, although there is no debate on the fact that Li mineralisation is of magmatic origin, related to fractional crystallisation of fluxing element-rich (B, F, P) hydrous melt, the behaviour of Li and other HFSE (Sn, Nb, Ta, W) during the hydrothermal *greisen* stage is still poorly understood.

The albite-lepidolite-topaz Beauvoir granite, located in the Sioule series of the northern French Massif Central (Do Couto et al., 2016), is an ideal evolved granite for studying the evolution of micas and the behaviour of Li from the magmatic to the hydrothermal stage. At Beauvoir, lepidolite is the primary Li-bearing mineral (averaging 20%), crystallising during the magmatic stage, with minor amblygonite-montebrasite (< 5%) as the second carrier (Cuney et al., 1992; Kosakevitch, 1976). The facies at the top of the intrusions are by far the richest in Li and metals, considered the most evolved part of the intrusion, and represent the main facies for a potential Li exploitation (Imerys website).

Descriptions of greisenisation in the Beauvoir evolved albitic granite remain surprisingly limited in the literature, and petrographic details are generally sparse. Only a few samples were investigated in the past for micas in the top part of the granite down to 250 m which represents the domain of interest for potential mining: three samples at 160, 194 and 209 m in Fonteilles (1987), two samples at 109 m and 278 m depth in Monier et al. (1987), one sample in Monnier et al. (2020), all from the GPF drill hole. Besides, a relatively exhaustive survey of the Li content of micas over the whole historical drill cores was done by Monier et al. (1987) below 200 m, and the trace element analyses carried out by LA-ICMS by Breiter et al. (2023b) with only two samples analysed above 250 m depth at 107 and 130 m. Early work (Cuney, 1992) emphasised that hydrothermal alteration in the Beauvoir granite is mostly inconspicuous except
in restricted fracture zones and at the very top of the cupola, where “classical quartz–muscovite fissure-type” greisen occurs. The petrographic basis for distinguishing greisen muscovite from muscovite in hydrothermally altered granite primarily relied on Merceron et al. (1987). Monnier et al. (2020) summarised the greisen assemblage in one sentence as the pervasive replacement of igneous minerals by muscovite–quartz–apatite, and Harlaux et al. (2025) defined the uppermost B1 unit as containing quartz–muscovite–topaz greisen. Our petrographic work does not support the strict synchrony of quartz, muscovite, and topaz in B1, and apatite relationships are ambiguous due to the long-lived and multi-generational apatite record in the Beauvoir system (Rocher et al., 2025).

The muscovite development in the top part of the Beauvoir intrusion appears from the new drilling campaigns as far more abundant than the classical fissure veins described in the kaolin quarry; quartz–muscovite replacement zones occur repeatedly in drilling down to 150–200 m depth, in places every ~5 m, showing a far more pervasive muscovitisation than previously documented.

Regarding formation conditions, two contrasting interpretations exist. Cuney et al. (1992) proposed a conventional greisen geometry controlled by volatile-rich magmatic fluids concentrated in the apical parts and fractures of the cupola, an interpretation also used to explain greisenisation in the nearby La Bosse stockwork. However, the equivalence between La Bosse Greisens and the Beauvoir muscovitisation process has never been demonstrated.

The main objectives of the present paper are: i) to study in detail the crystallisation sequence and chemistry of micas from the magmatic to the hydrothermal stage, ii) to determine the Li content and trace element composition of lepidolite and muscovite, and iii) to understand the behaviour of Li and other metals (Rb, Cs, Sn, Nb, Ta, W, etc.) during the magmatic-
hydrothermal transition in the most evolved unit and B1, characterised by the highest Li contents at the apex of the granite body. In particular, Li-rich micas from B1, known for their highest Li contents at the apex of the granite body, i.e., in the first 300 metres below the surface, are essential to characterise. To achieve these objectives, we conducted a detailed textural and chemical characterisation of drill cores taken from various locations and depths within the Beauvoir granite, focusing on the upper part (i.e., from the surface to a depth of 300m), which is the exploration target of the company IMERYS.

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## Geological context overview

The Beauvoir granite is part of the Echassières mining district in the northern part of the French Massif Central, within the Sioule metamorphic series (Fig. 1A; Do Couto et al., 2016; Schulz, 2009). This mining district comprises a variety of plutonic intrusions of Carboniferous age as well as polymetallic mineralisation, e.g., W in quartz veins (Mazet deposit and La Bosse stockwork), Sn in quartz-cassiterite veins (Chaillat and Montmins deposit), and Sb deposits (Nades deposit) emplaced during the collapse of the Variscan belt (Cuney et al., 1992). Three plutonic intrusions compose the mining district (Fig. 1B and C; Aubert, 1969; Cuney et al., 1992): i) the hidden La Bosse granite, ii) the two-mica ± cordierite granite of Colettes, and iii) the albite-lepidolite-topaz Beauvoir granite. Microgranite intrusions have also been recorded in the mining district as evidence of early magmatic events (Aubert, 1969). The Beauvoir albite-lepidolite-topaz granite is the last plutonic intrusion in the Echassières mining district. Thanks to the GPF-1 drilling program conducted in 1989, the Beauvoir granite is composed of three units, B3, B2, and B1, from bottom to top (Fig. 1C; Cuney et al., 1992).

The Beauvoir granite is currently the highest-grade lithiferous mica deposit, with total inferred resources estimated at 117 million metric tonnes (Mt) of ore, averaging 0.9% Li₂O (https://emili.imerys.com). The outcropping part shows kaolinite alteration, while the fresh

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granite is cut at depth by greisen veins and breccia that appear to follow a preferential NNE-SSW trend (Cuney et al., 1992). The B1 granite, hololeucocrate, is composed of albite, abundant colourless laths of lepidolite, and quartz, forming a framework filled with rare crystals of xenomorphic potassium feldspar, topaz, Li-rich phosphates, and Sn-Nb-Ta oxides. Compared with similar F-Li-rich igneous bodies such as the Yichun granite (Lin Yin et al., 1995; Huang et al., 2002; Li et al., 2015; Yin et al., 2022), the Beauvoir granite is enriched in Sn (200-1400 ppm), Ta (20-400 ppm), and Be (20-300 ppm), with the highest concentrations in the B1 unit, compared to other facies at depth (Cuney et al., 1992). According to Cuney et al. (1992), hydrothermal alteration is primarily localised on top of the granitic cupola, at the contact between the granite and the micaschist host rocks, and near fractures at deeper levels. Recent observations indicate that the most greisenised part is located close to the Colettes granite, e.g., in the northern part of the Beauvoir granite body, and develops along NE-SW-oriented fractured corridors.

## Sampling and analytical methods

The samples originate from the PER ("Permis Exclusif de Recherches", conducted in 2018) and EMILI (Project "Exploitation de Mica Lithinifère par Imerys" ongoing since 2021) drilling campaigns by IMERYS. The samples were selected to avoid the kaolinised zones of the first 30-40 meters. Twelve samples from the PER campaign and eighteen from the last EMILI campaign have been investigated (Fig. 1D). Geographically, the samples were collected from the northern, central, and southern parts of the Beauvoir quarry (Fig. 1D), providing information on the lateral variation in lithium distribution. Additionally, samples selected from different depths within the same borehole provide both lateral and vertical information. Fresh facies are hololeucocratic, rich in albite-quartz-lepidolite-topaz, and altered facies, called greisen, are grey to greenish, enriched in quartz-muscovite but with a more significant amount of muscovite than that expected by classic replacement of one
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feldspar by six quartz and one muscovite, when writing equations at constant aluminium
(Cathelineau and Kahou, 2024).

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All the facilities listed below are located at the GeoRessources laboratory in Nancy (France).

The samples were prepared into polished thin and thick sections for textural and chemical analyses. Petrographic features of the fresh and altered facies of the Beauvoir granite were examined using an Olympus BX51 microscope. Micas were selected based on size, and an elemental distribution map was obtained using a Bruker M4 Tornado micro-XRF. The conditions for the micro-XRF map were a 20 µm spot size, a step width of 30 µm, 16 ms times per pixel, and a current/intensity of 50 kV/600 µA. The two spectrometers were used for elemental mapping at 40 keV/130 kcps for each. The goal was to determine a relationship between mica size and Li content, and whether Rb could serve as a good proxy for lithium distribution. Back-scattered electron (BSE) images were obtained using a JEOL JSM-7600F scanning electron microscope (SEM) coupled to a wavelength-dispersive spectrometer (WDS).

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Quantitative analyses were performed using a CAMECA SX100 electron probe micro-analyser (EPMA) and calibrated using natural and synthetic materials, i.e., albite for Si and Na, MnTiO₃ for Ti, Al₂O₃ for Al, Fe₂O₃ for Fe, MnTiO₃ for Mn, olivine for Mg, andradite for Ca, orthose for K, RbTiPO₅ for Rb, pollucite for Cs, vanidinite for Cl, flap_P for P and Topaz for F. A current of 12 nA and an acceleration voltage of 15 kV were used. One spectrometer (PC1) was dedicated to fluorine measurement, with a counting time of 30 seconds. The counting time of Na, Si, Al, K, and P was 10s, 20s for Mg, 30s for Ca, Ti, Fe, Mn, Rb, Cl, and 240s for Cs. Total Fe is presented as FeO.

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The *in situ* major, minor, and trace elements (⁷Li, ⁹Be, ¹¹B, ²⁹Si, ⁴⁷Ti, ⁸⁵Rb, ⁹³Nb, ¹¹⁸Sn, ¹³³Cs, ¹³⁷Ba, ¹⁸¹Ta, and ¹⁸²W) were analysed using a quadrupole inductively coupled plasma mass spectrometry (ICP-MS) Agilent 7900 coupled with ESI New Wave 193nm Excimer laser ablation (LA) system. The following parameters were used: spot size of 30 µm, repetition rate

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182 of 5 Hz, fluence of 6 J/cm², and laser warm-up/washout of 30 s. Samples were ablated in a
183 stream of helium and transported to ICP-MS by a mixture of helium and argon gases.
184 Calibration was performed using NIST 610 and NIST 612 as external standards, and silica
185 (determined by EPMA) as the internal standard. Data reduction was performed using Iolite
186 software (Paton et al., 2011), based on the equations developed by Longerich et al. (1996).

187 The Li content of the micas was first estimated by EPMA using the empirical equations of
188 Tischendorf et al. (1997), which are similar to the pioneering equations developed by Tindle
189 and Webb (1990). These equations are based on SiO₂ content for trioctahedral micas and F
190 content for dioctahedral micas. The average Li₂O content in lepidolite is 5.3 wt%. The analysed
191 micas are rich in iron, which prevents the use of Tischendorf equations, as shown in Fig. 2. A
192 shift is observed between the calculated and measured values, which increases with the iron
193 content, reaching a few per cent at the maximum FeO content of approximately 7%. This
194 identified shift confirms previous observations, which considered the Tischendorf et al. (1997)
195 method as significantly underestimating the Li content (Tindle and Webb, 1990; Breiter et al.,
196 2019; 2023b; Van Lichtervelde et al., 2008), and LA-ICP-MS spots have thus been obtained in
197 the exact location of the EPMA analyses. Only the Li contents from the LA-ICP-MS analysis
198 were used to calculate the structural formulae for EMPA data points obtained at the exact
199 location before the LA-ICP-MS analysis. This constraint has limited the number of analytical
200 points compared to the classic EMPA approach.

201 Petrographic results: Sample description and textural characterisation by micro-
202 XRF

203 The mineralogy of the fresh and altered facies has been characterised with particular attention
204 to lepidolite and Li-rich micas.

205 *Fresh Granite*
206 Fresh granite is hololeucocratic and has a medium-sized millimetric granulometry (Fig. 3A).
207 Microscopic observations and composite chemical maps (Fig. 3B, C, D) allowed us to identify
208 the different minerals and their relative proportions (Kahou et al., 2025). In the fresh thick
209 section, the mineralogy consists of albite (average 45%), globular quartz (average 25%), and
210 lepidolite lath (average 20%), which form the rock framework. The interstices are then filled
211 by K-feldspar (< 10%), magmatic Li-phosphates and topaz (< 5%), and black, micrometric to
212 millimetric crystals corresponding to Sn-Nb-Ta oxides (< 1%). Under the microscope (Fig. 3
213 B), albite shows a characteristic polysynthetic macle, undistorted, indicating crystallisation in
214 a free environment. Lepidolite appears to be contemporary with or younger than albite. In most
215 samples, lepidolite appears as automorphic lamellar crystals, ranging in size from micrometric
216 to millimetric, and is frequently grouped as bouquets (Fig. 3C). It is the only phyllosilicate
217 present in the fresh granite. Abundant inclusions of oxide crystals (mainly cassiterite) are also
218 present in the lepidolite cleavages, as are thin layers of apatite and micrometric crystals of
219 quartz. Magmatic quartz, often multi-millimetre in size, rarely exhibits deformation textures.
220 They appear to have crystallised after albite, as evidenced by the albite inclusions within the
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222 In a series of samples (drilling EMI 10 at 182m depth, and EMI 18 at 174 m depth, for instance),
223 Li-rich micas exhibit more complex zoned textures with 3 to 4 zones characterised by
224 contrasting mean mass ("Z") as shown by back-scattered electron images (Fig. 3E, F). The core
225 of the lepidolite crystals is a Fe-rich mica characterised by an euhedral shape. Following the
226 growth bands develop in epitaxy, maintaining the same crystal orientation, as indicated by no
227 difference in extinction under crossed Nicols (Fig. 3F). Figures 3G and 3H confirm that the
228 core is Fe-rich. The growth band rim is the most frequently enriched in Rb relative to the core
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In most other samples, this core is not observed. The laths are generally thinner than the zoned crystals described above. Although already Rb-rich, they exhibit an internal growth band particularly enriched in Rb and Cs, which is easily identified under the back-scattered mode of the SEM (Fig. 4A from the rectangle indicated in Fig. 5B). Chemical mapping using the electron probe provided a high-resolution map of the square marked in Fig.4A. Fig. 4B and C show that the enrichment in Cs coincides with the Rb enrichment. It corresponds to a thin growth band (Fig. 5C). The enrichment is frequently discontinuous and affects only some laths of the larger crystal. They are intense and localised.

Figure 5 provides other examples of the distribution of the Rb-Cs-enriched growth zones (sample C39). The variation in the mean "Z" of the BSE mode is predominantly related to the Rb and Cs distribution (5 A and C). In these crystals, the iron content is very low and does not account for the changes in mean mass. Fig. 5 shows a very late Rb growth band. At the scale of crystals (Fig. 5B and D), the Rb and Cs rich zone is globally located at the periphery of the crystals. In another sample (C30), details of lepidolite laths show clear enrichments in the late growth zones of the lepidolite laths (Fig. 5E and 5F).

## Altered "greisen" facies

In hand samples and drill core, greisen alteration is characterised by the replacement of feldspars with a quartz-muscovite assemblage. A grey to greenish colour, due in part to the alteration of lepidolite, characterises the altered facies (Fig. 6A and B). The feldspars are partially to entirely replaced by hydrothermal muscovite and hydrothermal quartz (Fig. 6C). Hydrothermal muscovite is microcrystalline (Fig. 6C) and replaces all albites, which disappear. Topaz is almost absent in altered facies, while magmatic phosphates (i.e., amblygonite-group minerals) are replaced by hydrothermal phosphates (i.e., apatite and crandallite-group minerals). Although still present, the proportion of lepidolite decreases. As a result, modal proportions of muscovite (average 40%) and quartz (average 40%) increase while the
proportions of feldspar (< 10%) and lepidolite (< 10%) decrease. Lepidolite is partially replaced by muscovite only along cleavage planes. It forms a fringe growing at the lepidolite edge (Fig. 6D). The SEM-BSE microphotographs (Fig. 6E-F) show brighter rim domains corresponding to lepidolite, while dark domains represent muscovite replacement. Thus, although still present, the abundance of lepidolite proportionally decreases. Sometimes, lepidolite is almost wholly replaced by muscovite (Fig. 6E), resulting in fine lepidolite plates embedded in muscovite mass replacing the former lepidolite crystal (Fig. 6D and F). Lepidolite of altered facies loses one to two-thirds of its surface, leading to truncation of the grains (Fig. 6E, F). Oxide inclusions are rare in lepidolite from greisen facies. Apatite is often found in cleavage planes, although it mainly replaces magmatic phosphates. The crystallisation of fluorite in quartz-muscovite-rich fracture planes is noteworthy, with the main episode occurring after the greisen event.

The process of muscovitisation is not only occurring along microfractures and fractures, but also in the whole mass of the granite up to a few meters from the main fractures. Figure 7 shows the progressive development of muscovite replacing feldspars and lepidolite, up to the complete conversion of the original magmatic assemblage (albite-lepidolite-quartz-(K-feldspar) Fig. 7A) into a quartz-muscovite assemblage containing only minor lepidolite relics. Muscovite formation most commonly starts as a thin rim of tiny crystals around large lepidolite grains (Fig. 7B). It then develops by the infiltration of fluids along cleavage planes, where small muscovite crystals form, and by the infilling of microfractures that crosscut albite and K-feldspar (Fig. 7C and D). These microcracks continue into magmatic quartz as fluid-inclusion planes. With increasing alteration, muscovite flakes grow pervasively throughout the entire feldspar matrix (Fig. 7E), leading to the complete replacement of the early magmatic assemblage by a fine-grained quartz-muscovite matrix (Fig. 7F).

## The chemical composition of the micas
280 Main crystal-chemical features of the micas

281 According to textural characterisation, several types of micas have been distinguished: i) Fe-
282 rich micas in rare specific samples, ii) lepidolite overgrowth after Fe-cores, as well as the most
283 common lepidolites as laths from most samples, iii) the rim enriched in Rb and Cs on the edge
284 of lepidolites; iv) altered micas from the three first types; and v) the muscovite from altered
285 facies, replacing feldspar and Li rich micas. About 470 EPMA spots and 280 LA-ICP-MS
286 analyses were carried out. Only pairs of EMPA and LA-ICP-MS analyses conducted at the
287 exact location were considered for integrating Li measurements into the structural formulae.
288 Representative analyses and structural formulae of the five groups are presented in Table 1.

289 *The Mg-Li vs Fe+ Mn+Ti-Al<sub>v</sub> diagram (after Tischendorf et al., 1997)*

290 The data have been reported in the Mg-Li (apfu) vs Fe+Mg+Ti-AlVI (apfu) diagram (Fig. 8),
291 where the different colours in the captions distinguish the five populations described above.
292 The Fe-rich cores from micas in specific samples display a composition that falls outside the
293 lepidolite field, far from the zinnwaldite field, and correspond to Fe-Li-rich micas. The most
294 abundant populations of micas (overgrowths above Fe-Li-rich cores, and the common
295 lepidolites) are true lepidolites. Muscovites plot close to the pure muscovite end-member, with
296 a slight trend in the direction of the phengite field (Fig. 8). Lepidolites exhibit a broad spectrum
297 of major element compositions and plot significantly above most fields of lepidolite populations
298 reported in literature for differentiated granites and pegmatites, such as those of the Central
299 Iberian zone (Roda-Robles et al., 2006), Vietnam (Hien-Dinh and Gieré, 2016), Thailand
300 (Fanka and Thadtai, 2022), South Korea (Choi et al., 2024), Chen et al., 2022 (Altai, China).
301 This location in the lepidolite field is due to the high Li content, Fe content, and subsequent
302 lower Al(vi) content.

303 *Fe-Li-rich micas:* The Fe content of Fe-Li micas reaches 7.5% FeO in the core. The FeO
304 concentrations, however, remain high in their rims, decreasing only by a fraction of a percent
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or 1%. Therefore, these micas are rich in iron and somewhat Li from core to rim. Fe-Li micas
are predominant in a few samples found by chance, as no macroscopic features differentiate
these granites from their surrounding facies. These facies are pretty rare.

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Fe-Li-rich micas are also rich in manganese, as shown by the MnO-FeO/MnO diagram. Figure 9 presents the data obtained for Li-Fe-rich micas compared with those for lepidolite. In Figure 9a, the detailed sample-by-sample data are presented. In Figure 9b, the selected data, which include both ICP-MS and EMP analyses, along with the mica classification, are shown. The curved trends are considered magmatic, as they have also been observed in the GPF deep drilling for lepidolites (Esteves, 2025), except for the muscovite. The Fe-Li-rich cores are particularly rich in MnO and plot within domains typical of the deepest facies of Beauvoir (B3 unit). Most common lepidolites are characterised by much lower content of Fe and Mg.

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Lepidolites are characterised by a relatively high Li content around 28,000 ppm (mode of the population of lepidolite) corresponding to values around 3 apfu. Their MnO content varies from 0.1% to 0.5%, and their FeO content ranges from 0.15% to 2%. Rb₂O varies from 1 to 2.2, and Cs₂O from 0.05 to 0.4%. F varies between 8.5% and 10.5%.

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The Rb-Cs rich overgrowth in lepidolite laths: The brighter domains in lepidolite under BSE correspond to Rb and Cs enrichment, with Rb₂O and Cs₂O average content reaching up to 3 wt.%, thus 1% higher than the maximal value of lepidolite, and 1.3 wt.%, respectively, almost 1% higher than the maximal value of lepidolite. The enrichment in the growth band is abrupt and sometimes ceases abruptly, with the Rb content decreasing to values already observed in the rest of the crystal. Figure 10 shows the enrichment in both Rb and Cs in the external rims, compared to the whole population of lepidolite. The enrichment in caesium is by a factor of 5 to 6, and for Rb by a factor of 2. Fe-Li micas are slightly lower in Rb (10,000 to 13,000 ppm Rb) and have lower Cs values.

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*Muscovite*: muscovites are dioctahedral micas characterised by an interlayer where Rb and Cs are only minor traces. The tetrahedral occupancy by Si is close to the muscovite end-member (average 45 wt.% SiO₂, Si around 6 apfu). The octahedral site is dominated by aluminium (Al₂O₃ 23 wt.% on average, AlvI from 1.69 to 1.99) with lower Fe content than lepidolite (low celadonite contribution). The phengitic substitution is low, with FeO content around 1 wt.% in muscovite from feldspar alteration, but higher from 1.1 to 2.9 wt.% when muscovite is derived from lepidolite. Lithium is very low (Li₂O: 0.3 wt.%). OH mainly occupies the OH-F site, as F is lower than < 1 wt.%.

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## Li and metal content of Li-Fe micas

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*Lithium distribution:* As shown in Figure 11, trioctahedral micas from fresh facies have a Li content ranging from 19,000 to 32,000 ppm, with a mode around 26,000 ppm for Fe-Li micas, 30,000 ppm for lepidolite, and 28,000 ppm for Rb-Cs-rich rim in lepidolite. The mode at 25,000 ppm in the altered facies does not distinguish the different types of micas. In the altered facies, the range is far more extensive, with values between 20,000 and 25,000 ppm recorded, indicating that some crystals have been changed and have lost lithium. The laser spots are 30 micrometres wide and could have analysed both lepidolite and some muscovite layers interlayered within the lepidolite. However, as shown in Fig. 8, almost no data points indicate a chemical mixing with muscovite, as the typical trend for lepidolite is not oriented toward pure muscovite. Muscovite is characterised by a low, heterogeneous Li content of 10-700 ppm.

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## Metals in micas

**Two zoned Fe-Li micas** micas from the particular samples hosting the Fe-Li micas were investigated through LA-ICP-MS profiles to depict the metal behaviour in the melt and their incorporation into micas during the early stages (Fig. 12 and 13). In Fig. 12A, a synthetic map of three distinct growth phases (Fig. 12A) is distinguished using the chemical maps obtained
by micro-XRF (Fig. 12B, C, and D). These maps and the related profile (Fig. 12E, F, and G) show that the core is the most enriched in iron (up to 7.5% FeO), and that the overgrowths noted in 2 and 3 are only slightly enriched in Rb and Li, with a difference of less than 1,000 ppm in Li. The three zones are therefore not chemically distinct, although slight differences are easily mapped. The evolution of metal contents is also relatively moderate: an increase in Nb is noted in the periphery, and the other metals remain around the same range as in the centre of the crystal.

Similar observations were made in another crystal (Fig. 13A with microXRF maps in Fig. 13 B to F). Profiles show that Li content is approximately 25,000-28,000 ppm (Fig. 13B), and only one contrasting value was obtained in one rim, where 30,000 ppm was measured. Fe reaches 8% in the Fe-rich core, and Ti 1600 ppm (Fig. 13B). The distribution of Li and metals (Sn, Nb, W) is complex in detail, but does not show spectacular evolutions from the centre to the rim of the Fe-Li micas, in contrast to Fe and Ti.

If the details are complex, considering the entire population of analysed micas, the data show some evolution in metal concentrations with mica type (Fig. 14).

Fe-Li: The diagram in Fig. 14A shows that, across the five populations, regardless of mica Fe content, the Li content range remains relatively high, above 2.5 apfu.

Cs-Li: Fig. 14B confirms previous observations made based on the Rb-Cs diagram (Fig. 10). It discriminates the three populations of Li-micas, which have specific Cs contents from low values in Fe-Li micas to intermediate content around 2,000 ppm in lepidolites to an extensive range from 4,000 to 100,000 ppm Cs in Rb-Cs-rich rims.

Nb-Ta: the binary diagram Nb-Ta (Fig. 14C) shows significant differences in the incorporation of Nb and Ta in micas: Nb contents are the highest in the Fe-Li micas (between 280 and 360 ppm), and then decrease to 150 ± 50 ppm in lepidolites. The data obtained on lepidolites agree with those of Breiter et al. (03a) for three samples of the B1 unit. In addition, the trend of
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constant Nb and increasing Ta is typical of the Li-rich rim and represents one of the latest stages
of Li-mica crystallisation. Muscovites are very low in Nb and display Ta contents between a
few and 60 ppm.

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W-Sn (Li): continuous enrichment in W in micas from Fe-Li micas to lepidolite to Rb-Cs-rich rims Fig. 14 D and E). Sn shows a distinct behaviour, as it is present in equal amounts in both Fe-Li micas and lepidolite. It is slightly lower in the Rb-Cs-rich rim. W is not incorporated at all in the muscovite. On the contrary, Sn was incorporated at a higher level in muscovite, up to 1,000 ppm, which is about 3 times higher than in lepidolite (Fig. 14E).

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Discussion

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Substitution mechanisms and Li enrichment in micas

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As a preliminary conclusion, Li is characterised by high concentrations in Fe-Li micas and lepidolite and has a relatively homogenous distribution. Fe-Li micas are slightly less enriched in lithium (26,000 ppm) than lepidolites (29,000- 30,000 ppm). Based on previous work (Černý et al., 2003; Monier and Robert, 1986; Robert et al., 1993; Roda-Robles et al., 2006), four substitution mechanisms are involved in mica crystal-chemistry: i) $Li^+ + Si^{4+} \leftrightarrow R^{2+} + Al^{3+}$, ii) $Al^{3+} + \square \leftrightarrow Li^+ + (R^{2+})$, iii) $F^- \leftrightarrow OH^-$, iv) $Rb^+ + (Cs^+) \leftrightarrow K^+$ (where \square represents a vacancy in the octahedral site and $R^{2+}$ for octahedral cations $Fe^{2+}$, $Mg^{2+}$, $Mn^{2+}$). At the octahedral site, the high Li content explains why the $Al_{v1}$ is lower than in other lepidolites reported in the literature (Fig. 8).

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The Fe-Li micas represent a relatively rare occurrence of Fe-rich micas containing 7.15% to 8% FeO and 5.3% to 5.7% $Li_2O$. The unusual location of data points in the Fe+ Mn-Al$v1$ vs Mg-Li diagram of these Fe-Li micas and the proximity of lepidolite in the upper corner, indicating high Li and Fe and low $Al_{v1}$ contents, show that the Beauvoir granite micas are distinct from many other cases of micas from differentiated granites or pegmatites rich in Li (Fig. 8).
The increase in lithium from Fe-Li micas to lepidolite is primarily governed by Li availability in the magmas. It is incorporated in the crystallising mica following mass and electric balance equations (i) and (ii). The latter, on evolution from Fe-Li micas to lepidolite, most probably corresponds to a decrease in iron activity in the magma, which no longer allows the crystallisation of Fe-rich micas. Both micas (Fe-Li micas and lepidolite) are particularly rich in Li, indicating the availability of a large amount of Li in the melt since the very beginning of the magmatic activity, as the evolution occurs at slightly increasing Li content, except for a slight increase in Li. The evolution in the apical part of the B1 unit is therefore represented as shown in Fig. 15 for the magmatic stage noted I. The sub-stage Ia, corresponds to exceptionally preserved samples with inherited Fe-rich cores, b and c represents the most common case, with predominant lepidolite laths rich in lithium and overgrowths onto micas from Ia. The sub-stage c corresponds to the late overgrowths enriched in Rb and Cs. Finally, no mica crystallize during stage II a and b, defined as magmatic-hydrothermal transition, but during the muscovitisation stage noted IIc.

419

420 *Trace element distribution as the fingerprint of mica evolution*

The magmatic to hydrothermal evolution of the Beauvoir granite was mainly studied in the light of whole rock geochemistry and major element analyses of micas and Sn-Nb-Ta oxides during the GPF-1 drilling program of the Beauvoir granite (Cuney et al., 1992; Fonteilles, 1987; Monier et al., 1987; Ohnenstetter and Piantone, 1987; Raimbault et al., 1995; Wang, 1992). These previous works have highlighted the evolution of a single batch magma by fractional crystallisation over three periods, responsible for units B3, B2, and B1, from the least to the most differentiated, and a hydrothermal episode located mainly in the granitic cupola. The fluxing elements (F, B, and P) and alkaline elements (Li, Rb, Cs) increase from stage B3 to stage B1. Hydrothermal stage fluids are probably characterised by high Al and F content, as
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suggested by the nature of the muscovitisation process as deduced from whole-rock geochemistry. By contrast, such fluids are much lower in Li, Rb, and Cs.

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To date, trace element budget of micas has been extensively used to record granite and pegmatite evolution during both magmatic and hydrothermal processes (Benn et al., 2022; Garate-Olave et al., 2018; Han et al., 2021; Legros et al., 2016; Roda Robles et al., 1995; Van Lichtervelde et al., 2008; Vieira et al., 2011). Furthermore, Breiter et al. (2023a), in a comprehensive study, were the only authors to report trace-element compositions of micas from the Beauvoir granite in depth sections other than those presented here. Our data shows that the magmatic micas are represented by lepidolite *sensu lato*, which are replaced by muscovite during hydrothermal *greisen* alteration. The overall evolution is presented in Fig. 15 with the following evolutionary trends:

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*Lithium concentration evolution:* the Li content increases slightly from 2.7 to 3 apfu in the Fe-Li micas to 2.9 to 3.3 apfu in lepidolite. The Li increase in lepidolite is controlled by the partition coefficient and the Li content in the melt (Bea et al., 1994). The Li content must increase as fractional crystallisation progresses. In lepidolites, Li content is relatively homogeneous at the crystal scale. As Li is close to its maximal concentration, almost no core-to-rim increase is observed at the crystal scale.

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*Rb-Cs enrichment during the last stages of lepidolite crystallisation:* the Rb and Cs increase from core to rim may have been favoured by their high solubility, in magmas rich in fluxing elements (Cerny et al., 1985; Icenhower and London, 1996). Cs, in addition, is not incorporated by the main minerals that form rocks (quartz, two feldspars). The increased concentration of Rb and Cs in late crystallisation magmas (Tischendorf et al., 2001) may explain the Rb- and Cs-enriched rims observed in lepidolite. Furthermore, the low proportion of K-feldspar (another Rb-bearing mineral) in the early magmatic stage and the late K-feldspar crystallisation as an interstitial phase after lepidolite probably also contributed to increased Rb content in the melt.

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Lepidolite shows a low K/Rb (< 20 ratio at the mineralogical scale, suggesting a high degree of fractional crystallisation (Cerny et al., 1985; Marchal et al., 2014; Ballouard et al., 2016). In more detail, there is almost no correlation between Li content and the Rb enrichment in the rims. At the lepidolite crystal scale, the Rb increases from the core to the internal rim, followed by an Rb decrease from the internal to the external rim. The sharp decline in Rb in the external rim of lepidolite could indicate that the Rb-Ca enrichments correspond to an episodic fluid enrichment during a short event. The decrease at the very edge is sometimes attributed to reactions. Van Lichtervelde et al. (2008) reported reaction rims of lepidolite from the Tanco pegmatite that show loss of Rb, Cs, and Na, but gain in Si, K, and Li-F, in contrast to the Beauvoir granite.

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*Behaviour of metals (Sn-W, Nb-Ta):* Ta displays a higher solubility than Nb (Chevychelov et al., 2010; Linnen, 1998), which explains the significant precipitation of Nb-rich columbo-tantalite in the early magmatic stage, unlike columbo-tantalite richer in Ta and pyrochlore, which crystallise at the end of the magmatic stage. The Ta content in lepidolite shows this trend, with Ta-rich rims relative to the lepidolite core. We can therefore assume that late magmatic fluids were more concentrated in Ta than in Nb, which explains the higher Ta whole-rock content at the top of the intrusion (Cuney et al., 1992).

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Nb contents decrease from the Fe-Li micas to lepidolite because Nb solubility is low compared to Ta's. These metals reach saturation in the earlier magmatic stage. Nb-rich micas are mainly described in contexts where columbite cannot crystallise (Zhu et al., 2018). The early crystallisation of Fe-Li micas, i.e., before cassiterite and columbite-tantalite saturation, may explain their higher Nb contents. As soon as cassiterite and columbite-tantalite reach saturation, the metal budget decreases, which explains the lower content in lepidolite (both core and rim).

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Titanium has relatively low concentrations in all analysed micas: around 150 ppm in Li-Fe micas, a larger range in lepidolite (100-1000 ppm), and very low concentrations in the Rb-Cs rim of lepidolites. In Fe-Li micas, a possible redistribution of titanium has occurred, as indicated by the Ti-rich rim surrounding the core. Fonteilles (1987) has already observed such a redistribution, describing tiny micro-inclusions of TiO₂ around the core of Fe-Li-rich micas.

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There is no competitor for Ti incorporation, as Keppler (1993) demonstrated that RMGs are depleted in Ti-oxide minerals because the solubility of rutile is positively related to F content.

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As a result, the lepidolite core can incorporate all the Ti available in the early magmatic stage, leading to a drastic decrease in Ti in the late magmatic fluids and, consequently, in the lepidolite rims.

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As a partial conclusion, the metal distribution (in particular Rb, Cs, Ta, Nb, Sn, Ti, W) shows moderate variations in Li-rich micas (Li-Fe and lepidolite), and in some instances, a zoning from core to rim. There is a decrease in Nb from Fe-Li micas to lepidolite (Fig. 14). Conversely, in lepidolite, Rb, Cs, Ta, and W increase. These distributions first highlight changes in magma composition during crystal formation and, consequently, changes in element availability during fractional crystallisation (Bea et al., 1994), with some elements competing for incorporation into several mineral phases.

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*Evolution during the hydrothermal greisen stage*

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Muscovites: their lithium is relatively low (a few tens of ppm up to 150 ppm), although they replace or degrade lepidolites. The phengitic substitution is very low and is associated with iron, reaching 0.13-0.20 in some crystals. Muscovites are therefore very close to the pure end-member.

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As the Li content of lepidolite from fresh and altered facies is quite similar, this suggests that greisen alteration does not significantly impact lithium content at the crystal scale of the preserved lepidolite. The substantial decrease in whole-rock lithium content is due to a

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significant replacement of lepidolite layers by muscovite, which is almost lithium-free. The proportion of lepidolite, approximately 20% in fresh facies, decreases by a factor of 2 or 3 (i.e., from around 5% to 10%) while the muscovite population increases by over 30% (Kahou et al., 2025). While lepidolite loses almost no lithium, the whole granite loses lithium during greisen alteration (Cuney et al., 1992; Raimbault et al., 1995). As a result, the stock of metals (i.e., Rb, Cs, Nb, Ta, W, Ti) carried by lepidolite at the magmatic stage decreases during the greisen episode (Fig. 15, stage IIc as defined by Rocher et al., 2024). The Li content of hydrothermal muscovite ranges from very low values, i.e., 6 ppm to 700 ppm Li. Therefore, muscovite does not recover lithium lost by lepidolite during greisen alteration. The same is true for the other newly formed minerals, i.e., hydrothermal quartz and apatite from the greisen episode, which exhibit very low Li contents of 30 ppm and 10 ppm, respectively. Consequently, Li released during greisenisation has been lost outside the granite body. It does not necessarily explain the geochemical halos identified in the micaschists hosting the Beauvoir granite, as reported by Aubert (1969), Piantone and Burnol (1987), and Cuney et al. (1992). Fonteilles (1987) has shown that the main effect of the granite intrusion on micaschist is the formation of Fe-micas (biotites) rich in lithium. This lithium contribution is probably sufficient to explain the halos. Suppose the stable phase during greisenisation is a muscovite free of lithium, as shown by all analytical work. In that case, this is not a good candidate to host the lithium lost by lepidolite and Fe-Li micas, whatever the host rock (granite or micaschists), contrary to the hypothesis of Li contamination during the greisen stage. So Li may have been entirely lost to convective fluids rather than being trapped close to the Beauvoir intrusion.

Similar conclusions can be addressed regarding Rb and Cs. Figure 9 shows that the Rb and Cs contents of lepidolite from both fresh and altered facies are almost identical. A part of the Rb and Cs stock has been lost due to the dissolution of lepidolite (and possibly K-feldspar). Only a part could have been scavenged by muscovite, with Rb content ranging from 100 to 6,000
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ppm. Some muscovite laths replacing lepidolite have shown, in particular, higher Rb contents (average > 2,500 ppm), a content higher than that of muscovite replacing feldspars (average < 2,500 ppm). The Cs contents in muscovite are far too low to consider muscovite as a possible trap for the lost Cs.

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The Nb and Ta contents are much higher in fresh or altered lepidolite (between 75 and 370 ppm and 20 and 430 ppm for Nb and Ta, respectively) than in muscovite (between 1 and 35 ppm and 1 and 80 ppm for Nb and Ta, respectively). Since muscovite did not incorporate Nb and Ta during the hydrothermal *greisen* stage, Nb and Ta lost from lepidolite could have been incorporated into the hydrothermal columbite-tantalite. Thus, Ohnenstetter and Piantone (1987) and Belkasmi and Cuney (1998) have demonstrated that CGM from the Beauvoir and Montebras granites (French Massif Central) exhibit rims enriched in Nb, associated with Sn, Ti, and Fe. These rims could, therefore, represent hydrothermal overgrowths formed by the *greisen* fluid.

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Lepidolite from Beauvoir has low Sn (between 70 and 700 ppm, average 170 ppm) and W (100 to 700 ppm, average 300 ppm) contents. The crystallisation of cassiterite during the early magmatic phase resulted in Sn fractionation, leading to low Sn concentrations in magmatic lepidolite, as noted for the Cínovec pluton by Breiter et al. (2019). Similarly, since no wolframite has been found and the crystallisation of wolframite at the magmatic stage in evolved granitic melts is still controversial (see Che et al., 2013), we can assume that the low to high W content of lepidolite reflects the incorporation of almost all the W present at the early magmatic stage into CGM and lepidolite (Cuney et al., 1992). In the greisen system, hydrothermal muscovites exhibit significantly elevated tin content, averaging ~700 ppm, about three to four times higher than magmatic lepidolites (~175–230 ppm). This level of enrichment aligns well with ranges reported in the broader geochemical literature. For example, Lehmann (2021), in his review on the formation of tin ore deposits, highlights that hydrothermal micas

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(especially in greisen systems) commonly host hundreds of ppm of Sn, emphasising the role of mica as a significant sink for tin in magmatic-hydrothermal systems. This suggests that the greisenizing fluid in Beauvoir was strongly enriched in Sn, likely as halide complexes (Sn-Cl), enabling incorporation of Sn⁴⁺ into the muscovite structure by substitution of Al³⁺ in tetrahedral or octahedral sites. Additional Sn may also be stored in micro-inclusions of Sn-rich fluid within the mica. Part of this Sn appears to derive from the partial dissolution and redistribution of preexisting magmatic cassiterite, implying that greisenisation redistributed, rather than generated, a significant part of the tin. The contrast between muscovite and lepidolite thus underscores the importance of late-stage, fluid-mediated metasomatism (including the remobilisation of earlier Sn-bearing phases) in controlling tin distribution in the system.

In contrast, the low W content (up to 20 ppm) in muscovite suggests that W was either i) incorporated into the reaction rims (i.e., patchy zoning) of the hydrothermal CGM or ii) removed from the system. For example, Monnier et al. (2022) argue that W from lepidolite was mobilised by greisen fluid outside the Beauvoir system and crystallised as wolframite veins in the La Bosse ferberite stockwork. However, this stock work is considered earlier than the Beauvoir granite. Conversely, Michaud et al. (2020) have shown that remobilisation of W can occur within the granite, as demonstrated in other instances, by the presence of minor wolframite in intragranitic veins (case of the Argemela district (Portugal)).

At Beauvoir, lepidolite is the main Ti-bearing mineral during the magmatic stage, with Ti contents ranging from 20 to 2,000 ppm. During hydrothermal greisen alteration, Ti is partially leached from lepidolite and incorporated into muscovite at variable concentrations of 3-800 ppm.

Muscovites display a very high K/Rb ratio (30 up to 80), suggesting a crystallisation from an Rb-poor and K-rich aqueous fluid responsible for lepidolite alteration during hydrothermal greisen episodes. The richness in K is necessary because the main alteration reaction is the
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albite-to-muscovite conversion. K may come from the K-feldspar alteration, as in many greisen.

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Still, this contribution is probably insufficient to account for the complete conversion of the
albite-granite, which is poor in K-feldspar. The high Ba content of muscovite (up to 735 ppm;

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see Table 1) compared with lepidolite (up to 170 ppm; see Table 1) provides an argument in
favour of the involvement of a meteoric fluid dissolving K-feldspars outside the Beauvoir
granite and bringing Ba during the crystallisation of secondary muscovite.

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About the involvement of meteoric fluids, most available isotopic data support a significant
contribution of meteoric-derived water to the greisen-forming fluid in the Beauvoir granite.

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Fouillac et al. (1987) measured δ¹⁸O whole-rock values between +4.6‰ and +8.6‰ (SMOW) in the upper B1–B2 units, and δD values for hydrothermal K-micas varying from –105‰ to –55‰, far lighter than expected from a closed magmatic fluid system. These isotopic signatures

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strongly suggest infiltration of an external, isotopically “light” fluid, interpreted as meteoric
water introduced during hydraulic fracturing at the liquidus-solidus transition (Fouillac et al.,

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1987). Fonteilles (1987) and Monnier et al. (1987) documented that the late-stage (post-
magmatic) muscovite overprinting albite and lepidolite has a distinct, homogeneous chemical

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composition, consistent with crystallisation from an external hydrothermal fluid rather than
from residual melt (Fonteilles, 1987). Moreover, experimental data show that the Beauvoir

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granite solidus is unusually low (around ~550 °C), enabling conditions under which a meteoric-
modified fluid could drive quartz–muscovite alteration. (Pichavant, 2022). Experimental and

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petrological constraints (low solidus temperatures and evidence for fluid boiling/flashing)
provide a viable physical mechanism for the introduction and mixing of meteoric water via

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fracture networks and the hydraulic fracturing of a crystallising cupola, producing the boiling
episodes that drive pervasive quartz–muscovite alteration and distal veining. Recent SIMS

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oxygen-isotope measurements on hydrothermal apatite from the alteration zone reveal δ¹⁸O
values ranging from –9‰ to +13‰, best explained by a progressive mixing between reduced

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magmatic and oxidised meteoric fluids during greisenisation (Rocher et al, 2023, 2025).

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Altogether, the stable-isotope systematics of O and H in combination with mica chemistry and

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petrographic support a model in which a late, externally-influenced (magmatic + meteoric)

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hydrothermal event—rather than a strictly closed orthomagmatic fluid—was principally

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responsible for the extensive muscovitisation observed at Beauvoir.

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*Overall evolution of the lithium stock in the granite*

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The muscovitisation episode appears disconnected from the magmatic evolution and cannot be

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considered part of a magmatic-to-hydrothermal transition cycle. Compared with other lithium-

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rich magmatic systems, no transitional term towards lithium-rich muscovites or phengites has

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been observed. The fluids responsible for muscovitisation drained by the fractures contributed

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to a reduction in the mass of lepidolites and therefore to a significant decrease in the available

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lithium mass along the corridors where they circulated.

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As lepidolite is the main Li-bearing mineral phase, its volume decrease from 20-22 to 10-12%

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in the greisen corresponds, grossly, to a reduction of Li from 0,6-0.64 to 0,28-0.35 wt.% Li in

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the rock. Such a decrease is typically observed in the last drilling campaigns, particularly in

619

zones close to the Colettes contact where greisens are abundant. The intersected greisen lengths

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range from meters to several meters, and, exceptionally, to a few tens of meters, and the number

621

of significant greisen zones in the first 300m depth varies between 1 and 4/5 zones.

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## Conclusions

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The highly fractionated upper unit B1 of the Beauvoir intrusion is dominated by a quartz-

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lepidolite-albite- (topaz, minor K-feldspar) assemblage.

626-

Two mica types are distinguished: (i) rare, locally preserved trioctahedral Fe-Li micas, and (ii)

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lepidolite, which predominates in all unaltered magmatic facies with Li contents of 28,000 ±

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1000 ppm and late Rb-Cs (Ta) enrichment.
629- Hydrothermal dioctahedral muscovite develops along SW-NE oriented fracture corridors and
dense micro-fissure networks, replacing feldspars and lepidolite. This muscovitisation reduces
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lepidolite from ~20% to 5-10%, causing significant Li loss at the rock scale, while Sn is partly
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reincorporated (up to 1,400 ppm). Although residual lepidolite retains its Li at the crystal scale,
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hydrothermal alteration redistributes and partially exports metals, decoupled from magmatic
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evolution.
634

635- These findings demonstrate the critical role of hydrothermal muscovitisation in controlling
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metal mobility and appear disconnected from Beauvoir's magmatic evolution.

637 The hydrothermal stage negatively impacted lithium stock and recovery potential, as muscovite
638 acts as a Li-poor diluent in mica concentrates. Li loss by hydrothermalism is heterogeneous at
639 the scale of the pluton. It is a function of the distribution of greisenised corridors, which explains
640 why the centre and the southern part of the intrusion, which are better preserved, constitute the
641 primary targets of the industrial project.

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643

Data availability

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The data supporting the findings of this study, i.e., representative EPMA and LA-ICP-MS analyses of the micas, as well as the geographical coordinates of the analysed samples, are available upon request from the corresponding author, Michel Cathelineau. The data are not publicly available due to restrictions from Imerys, as they also form part of an ongoing exploration campaign.

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Acknowledgments

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The authors thank IMERYS and all the geologists, especially Benjamin Barré and Alyson

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Bargain, for providing access to the Beauvoir quarry and for their assistance during the drill

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core sampling. This work was supported by the French National Research Agency through the

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national program "Investissements d'avenir" with the reference ANR-10-LABX-21-

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RESSOURCES21. Olivier Rouer and Lise Salsi from the Service Commun de Microscopie

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Électronique et de Microanalyse (SCMEM, Université de Lorraine, Nancy, France) are thanked

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for their assistance during EPMA and micro-XRF acquisition. Drs. C. Ballouard, L. Monnier,

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O. Rocher, C. Korbel, and N. Mezoued are thanked for numerous discussions about the genesis

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of rare-metal metal granites and mica geochemistry, which significantly improved the present

660

version. Analyses were carried out at the SCMEM and LA-ICP-MS platforms of

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GeoRessources in Nancy, which are funded by Labex Ressources 21 (ANR-10-LABX-21-

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RESSOURCES21), the Region Lorraine, and the European Community through the FEDER

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program. Prof. K. Breiter is gratefully acknowledged for his pertinent comments and

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suggestions, which have led to a significantly improved version of the manuscript. Two

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anonymous reviewers are also thanked for their relevant suggestions.

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670 References

671 Aubert, G., 1969. Les coupoles granitiques de Montebras et d'Échassières: (Massif Central français) et la genèse de leurs minéralisations en étain, lithium, tungstène et béryllium, Mémoires du B.R.G.M, 46, 345 pp.

674 Ballouard, C., Poujol, M., Boulvais, P., Branquet, Y., Tartèse, R., Vigneresse, J.-L., 2016. Nb-Ta fractionation in peraluminous granites: A marker of the magmatic-hydrothermal transition. Geology 44, 231-234. https://doi.org/10.1130/G37475.1

677 Bea, F., Pereira, M.D., Stroh, A., 1994. Mineral/leucosome trace-element partitioning in a peraluminous migmatite (a laser ablation-ICP-MS study). Chem. Geol., Special issue, Trace-element Partitioning with Application to Magmatic Processes, Foley F. and Can des Laan S. eds, 117, 1-4, 291-312. https://doi.org/10.1016/0009-2541(94)90133-3

681 Belkasmi, M., Cuney, M., 1998. Les columbo-tantalites zonées du granite de Montebras (Massif Central Français). Implications pétrogénétiques. C. R. Acad. Sc. IIA, 326, 459-465.

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<figure><img src="image_2.png" /></figure>

Figure 1: Location and simplified geological map of the Echassières district and Beauvoir granite. A) The study area is located in the French Massif Central (FMC). B) Simplified geological map of the Echassières district (modified from Monnier et al., 2020). C) Schematic cross-section of the Beauvoir granite showing the vertical magmatic zoning and the three units, B3, B2, and B1, from bottom to top (modified from Cuney et al. (1992) and Harlaux et al. (2017)). D) Location of drillings from the first campaign (North, Per N, Centre, Per C; South, Per South) and 2023-2024 campaign (EMI 00x, only x is indicated on the map). GPF: drilling carried out under the framework of the Géologie Profonde de la France (GPF) program.
<figure><img src="image_3.png" /><figcaption>Fig. 2: FeO vs Li₂O diagram applied to data obtained using EMPA and LA-ICP-MS. When calculated using Tischendorf's equation, the shift towards lower values is significant, reaching 2-3% when FeO reaches 8%. The indicated values correspond to Li content in ppm.</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>Figure 3: A) Hand sample showing the typical texture of Beauvoir fresh granite. B) Cross-polarised light (XPL) macroscopic photography of a thin section showing the mineralogy of the Beauvoir granite. C) The XPL photograph shows the framework of the fresh facies with albite, lamellar lepidolite, and quartz. D) Composite micro-XRF image showing the chemical distribution and mineralogy of the Beauvoir granite, showing Fe-Rb-rich lepidolite in pink, albite in dark red, K feldspar in yellow-orange, and quartz in grey. E) BSE images showing Fe-Li micas with a core slightly enriched in iron, the whole crystal being rich in iron. F) Fe-Li-rich mica with an euhedral core (G, H) Rb and Fe chemical maps issued from micro-XRF, for Fe-Li micas with a large Fe-rich core, and a border enriched in Rb. Qz = quartz, Ms = muscovite, Lpd = lepidolite, Ab = albite, Kfs = K-feldspar</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>Fig. 4: A) BSE images showing typical lepidolite crystals in the most common representative samples. B and C) The localised enrichment in Rb and Cs is demonstrated by the EMP images on the small square shown in Fig. A. lpd: lepidolite; qtz: quartz.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>Fig. 5: A) BSE images showing typical lepidolite crystals in the most common representative samples. B) The micro-XRF images of rubidium are done on a larger area than the image presented in Fig. A. The XRF image shows the heterogeneity in the Rb distribution. C) Magnification of the square C in Fig. A. D) Caesium distribution on the same area as that of the image in B, E, F) distribution of Rb in typical lepidolite crystals with enrichment at the rim.

Lpd: lepidolite; qtz: quartz.</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>Figure 6:</figcaption></figure>

A and B) Hand sample showing the typical texture of Beauvoir muscovitised granite, in A with a greenish colour due to the muscovitised lepidolite, and B showing the deep penetration of the pervasive muscovitisation and almost total replacement of albite and part of the lepidolite. C, D) Microphotographs of thin sections and SEM images showing the petrography of a typical Beauvoir granite altered facies. C) XPL macroscopic photography of a thin section showing the main greisen facies mineralogy of the Beauvoir granite, i.e., albite and microcline replacement. D) partial replacement of lepidolite. E, F) SEM-BSE microphotographs show total lepidolite replacement by muscovite (E) and microscale lepidolite replacement by muscovite following the cleavages (F). Qz = quartz, Ms = muscovite, Lpd = lepidolite, Ab = albite, Kfs = K-feldspar, Ap = apatite.
<figure><img src="image_8.png" /><figcaption>Figure 7: Stages of granite muscovitisation. A: original magmatic assemblage (albite (ab)– lepidolite (lpd)–quartz (qtz)–(K-feldspar)); B: thin rim of tiny crystals around a large lepidolite grain as well as along cleavage planes; C: extensive development of muscovite around lepidolite; D: muscovite infilling of microfracture that crosscut albite and K-feldspar and lepidolite with subsequent alteration; E: pervasive muscovitisation of albite; F: full replacement of the original granite assemblage by muscovite and quartz, with rare lepidolite relics.</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>Figure 8: Fe+ Mg+Ti-AlvI vs Mg-Li diagram from Tischedorf applied to the five types of micas from Beauvoir. Comparison with lepidolite trend from other differentiated granites in the world: a: South Korea (Choi et al., 2024); b: Hien-Dinh and Gieré (2017); c: Mt Mica, Canada (Marchal et al., 2014) ; d: Altai, China (Chen et al., 2022).</figcaption></figure>
<figure><img src="image_10.png" /><figcaption>Figure 9: MnO vs FeO/MnO diagram applied to micas from the upper part of the B1 facies. The data are presented as a function of the sample noted by drilling numbers and depth (EMI xy for the name of the drilling, followed by the depth in m (for instance 10-182 for EMI 0010-182 m); N, C, S for the 2018 drilling campaign. The inset provides the same information as the representative analyses chosen for the paper, with the five mica populations defined in the caption.</figcaption></figure>
<figure><img src="image_11.png" /><figcaption>Figure 10: Rb vs Cs diagram for the five populations of micas. The diagram shows the increased content of Rb on lepidolites, and Cs in particular, in the Rb-Cs-rich rims. Red circles: Fe-Li micas; dark blue circles: lepidolite; light blue: undifferentiated Fe-Mi micas and lepidolite in altered granites; orange circles: Rb-Cs rich lepidolite overgrowths; green circles: muscovite.</figcaption></figure>
<figure><img src="image_12.png" /></figure>

Figure 11: Histogram showing Li content in lepidolite for the five populations of micas

Altered corresponds to altered facies with mixed populations.
<figure><img src="image_13.png" /><figcaption>Figure 12: Chemical maps and LA-ICP-MS analysis along a profile carried out in a Fe-Li mica, crosscutting the large core and the overgrowth. 1: core, 2 and 3: overgrowths (white numbers). Numbers in black correspond to the LA-ICP-MS analyses.</figcaption></figure>
<figure><img src="image_14.png" /><figcaption>Figure 13: Chemical maps and LA-ICP-MS analysis along a profile carried out in a second example of Fe-Li mica, crosscutting the large core and the overgrowth. 1: core, 2 and 3: overgrowths (white numbers). Numbers in black correspond to the LA-ICP-MS analyses.</figcaption></figure>
<figure><img src="image_15.png" /><figcaption>Figure 14: Relationships between Li content and other elements (Fe, Cs, W, Sn), and Nb-Ta binary plot for the five populations of micas.</figcaption></figure>
<figure><img src="image_16.png" /><figcaption>Fig. 15: Schematic and synthetic overview of the textures and metal contribution or losses occurring during the four major stages of mica crystallisation in the Beauvoir granite. The stages I and IIC refer to the mineral sequence proposed by Rocher et al. (2024).</figcaption></figure>

982

983

984

985

986

987
Table captions

Table 1: Representative EPMA compositions of the trioctahedral and dioctahedral micas and corresponding LA-ICP-MS selected trace element concentrations, for the four major types of micas (Li-Fe micas, Lepidolite (Lpd), Rb-rich lepidolite rim (Rb-rim), and muscovite (Ms)). Structural formulae were calculated using the Li concentration obtained using LA-ICP-MS.

<table><thead><tr><th>Drilling-Depth (m)</th><th>Li-Fe<br>mica</th><th>Li-Fe<br>mica</th><th>Li-Fe<br>mica</th><th>Lpd</th><th>Lpd</th><th>Lpd</th><th>Rb-rim</th><th>Rb-rim</th><th>Rb-rim</th><th>Ms</th><th>Ms</th><th>Ms</th></tr></thead><tbody><tr><td>SiO<sub>2</sub></td><td>45.80</td><td>45.85</td><td>45.89</td><td>51.21</td><td>52.12</td><td>54.31</td><td>49.30</td><td>52.16</td><td>52.67</td><td>45.57</td><td>46.51</td><td>46.10</td></tr><tr><td>TiO<sub>2</sub></td><td>0.17</td><td>0.18</td><td>0.24</td><td>0.10</td><td>0.03</td><td>0.04</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.03</td><td>0.00</td></tr><tr><td>Al<sub>2</sub>O<sub>3</sub></td><td>23.32</td><td>22.95</td><td>23.84</td><td>24.28</td><td>23.09</td><td>24.11</td><td>23.02</td><td>22.26</td><td>21.07</td><td>37.43</td><td>37.41</td><td>37.26</td></tr><tr><td>FeO</td><td>8.00</td><td>7.82</td><td>7.63</td><td>0.57</td><td>0.36</td><td>0.46</td><td>1.82</td><td>0.37</td><td>1.13</td><td>0.15</td><td>0.23</td><td>0.39</td></tr><tr><td>MnO</td><td>0.69</td><td>0.87</td><td>0.70</td><td>0.15</td><td>0.08</td><td>0.27</td><td>0.45</td><td>0.23</td><td>0.05</td><td>0.09</td><td>0.07</td><td>0.16</td></tr><tr><td>MgO</td><td>0.33</td><td>0.35</td><td>0.32</td><td>0.05</td><td>0.02</td><td>0.04</td><td>0.04</td><td>0.03</td><td>0.04</td><td>0.05</td><td>0.04</td><td>0.03</td></tr><tr><td>CaO</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.01</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td></tr><tr><td>Na<sub>2</sub>O</td><td>0.51</td><td>0.48</td><td>0.53</td><td>0.41</td><td>0.29</td><td>0.35</td><td>0.31</td><td>0.31</td><td>0.27</td><td>0.10</td><td>0.06</td><td>0.13</td></tr><tr><td>K<sub>2</sub>O</td><td>10.01</td><td>9.94</td><td>10.05</td><td>10.62</td><td>10.32</td><td>10.35</td><td>9.49</td><td>9.27</td><td>9.55</td><td>10.89</td><td>10.31</td><td>11.06</td></tr><tr><td>Rb<sub>2</sub>O</td><td>1.33</td><td>1.31</td><td>1.26</td><td>1.55</td><td>2.08</td><td>1.19</td><td>2.60</td><td>3.10</td><td>2.70</td><td>0.26</td><td>0.44</td><td>0.52</td></tr><tr><td>Cs<sub>2</sub>O</td><td>0.01</td><td>0.02</td><td>0.04</td><td>0.07</td><td>0.57</td><td>0.05</td><td>1.25</td><td>1.24</td><td>1.08</td><td>0.01</td><td>0.01</td><td>0.02</td></tr><tr><td>P<sub>2</sub>O<sub>5</sub></td><td>0.13</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.05</td><td>0.02</td><td>0.06</td><td>0.01</td><td>0.00</td><td>0.01</td><td>0.06</td></tr><tr><td>F</td><td>7.22</td><td>7.27</td><td>7.23</td><td>8.32</td><td>8.15</td><td>9.66</td><td>8.42</td><td>8.86</td><td>8.86</td><td>0.00</td><td>0.11</td><td>0.17</td></tr><tr><td>(F=O)*</td><td>3.04</td><td>3.06</td><td>3.04</td><td>3.50</td><td>3.43</td><td>4.07</td><td>3.55</td><td>3.73</td><td>3.73</td><td>0.00</td><td>0.05</td><td>0.07</td></tr><tr><td>Li<sub>2</sub>O*</td><td>3.58</td><td>3.59</td><td>3.60</td><td>5.14</td><td>5.40</td><td>6.04</td><td>4.59</td><td>5</td><td>5.56</td><td>0.01</td><td>0.10</td><td>0.15</td></tr><tr><td>Li (ppm) LA-ICP-MS</td><td>26,500</td><td>26,447</td><td>26,385</td><td>30,115</td><td>30,128</td><td>29,454</td><td>28,811</td><td>29,942</td><td>30,865</td><td>13</td><td>67</td><td>88</td></tr><tr><td>Li<sub>2</sub>O-% ICP</td><td>6</td><td>6</td><td>6</td><td>6</td><td>6</td><td>6</td><td>6</td><td>6</td><td>7</td><td>0</td><td>0</td><td>0</td></tr><tr><td>Cs (ppm)</td><td>291</td><td>308</td><td>303</td><td>908</td><td>4391</td><td>984</td><td>10,546</td><td>6820</td><td>3908</td><td>55</td><td>48</td><td>279</td></tr><tr><td>Rb (ppm)</td><td>12,411</td><td>12,862</td><td>12,337</td><td>13,660</td><td>17,134</td><td>14,952</td><td>21,742</td><td>23,283</td><td>21,310</td><td>2535</td><td>1230</td><td>4479</td></tr><tr><td>Nb (ppm)</td><td>339</td><td>316</td><td>316</td><td>113</td><td>193</td><td>128</td><td>116</td><td>174</td><td>178</td><td>1</td><td>7</td><td>5</td></tr><tr><td>Sn (ppm)</td><td>174</td><td>176</td><td>174</td><td>194</td><td>121</td><td>151</td><td>117</td><td>99</td><td>137</td><td>33</td><td>525</td><td>472</td></tr><tr><td>Ta (ppm)</td><td>107</td><td>98</td><td>93</td><td>39</td><td>83</td><td>34</td><td>186</td><td>102</td><td>98</td><td>1</td><td>27</td><td>10</td></tr><tr><td>W (ppm)</td><td>160</td><td>147</td><td>162</td><td>168</td><td>463</td><td>249</td><td>307</td><td>339.00</td><td>405</td><td>0</td><td>2</td><td>9</td></tr><tr><td>Ba (ppm)</td><td>13.12</td><td>10.71</td><td>11.99</td><td>3.29</td><td>0.98</td><td>3.40</td><td>2.66</td><td>1</td><td>4.63</td><td>175.45</td><td>27.20</td><td>630.00</td></tr><tr><td>Ti (ppm)</td><td>1543</td><td>1508</td><td>1398</td><td>363</td><td>162</td><td>165</td><td>45</td><td>24.80</td><td>92</td><td>6</td><td>18</td><td>0</td></tr><tr><td>Nb (ppm)</td><td>338.57</td><td>315.89</td><td>315.60</td><td>112.78</td><td>192.91</td><td>127.79</td><td>116.00</td><td>174.00</td><td>177.85</td><td>0.62</td><td>0.26</td><td>5.17</td></tr><tr><td>Nb/Ta</td><td>3.17</td><td>3.22</td><td>3.39</td><td>2.87</td><td>2.32</td><td>3.79</td><td>0.62</td><td>1.71</td><td>1.81</td><td>0.47</td><td>0.26</td><td>0.54</td></tr><tr><td>Total</td><td>98.06</td><td>97.58</td><td>98.30</td><td>98.99</td><td>99.09</td><td>102.85</td><td>97.77</td><td>99.58</td><td>99.26</td><td>94.56</td><td>95.28</td><td>95.97</td></tr><tr><td>Si (IV)</td><td>5.94</td><td>5.98</td><td>5.93</td><td>6.33</td><td>6.48</td><td>6.46</td><td>6.29</td><td>6.50</td><td>6.09</td><td>6.15</td><td>6.10</td><td>6.10</td></tr><tr><td>Ti</td><td>0.02</td><td>0.02</td><td>0.02</td><td>0.01</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td></tr><tr><td>Al (IV)</td><td>2.06</td><td>2.02</td><td>2.07</td><td>1.67</td><td>1.52</td><td>1.54</td><td>1.71</td><td>1.50</td><td>1.91</td><td>1.85</td><td>1.90</td><td>1.90</td></tr><tr><td>Al (VI)</td><td>1.51</td><td>1.51</td><td>1.57</td><td>1.87</td><td>1.86</td><td>1.84</td><td>1.75</td><td>1.77</td><td>3.98</td><td>3.97</td><td>3.91</td><td>3.91</td></tr><tr><td>Al (T)</td><td>3.57</td><td>3.53</td><td>3.63</td><td>3.54</td><td>3.38</td><td>3.38</td><td>3.46</td><td>3.27</td><td>5.89</td><td>5.83</td><td>5.81</td><td>5.81</td></tr><tr><td>Fe</td><td>0.87</td><td>0.85</td><td>0.83</td><td>0.06</td><td>0.04</td><td>0.05</td><td>0.19</td><td>0.04</td><td>0.12</td><td>0.02</td><td>0.03</td><td>0.04</td></tr><tr><td>Mn</td><td>0.08</td><td>0.10</td><td>0.08</td><td>0.02</td><td>0.01</td><td>0.03</td><td>0.05</td><td>0.02</td><td>0.01</td><td>0.01</td><td>0.02</td><td>0.02</td></tr><tr><td>Mg</td><td>0.06</td><td>0.01</td><td>0.06</td><td>0.01</td><td>0.00</td><td>0.01</td><td>0.01</td><td>0.00</td><td>0.01</td><td>0.01</td><td>0.01</td><td>0.01</td></tr><tr><td>Ca</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td></tr><tr><td>Na</td><td>0.13</td><td>0.12</td><td>0.13</td><td>0.10</td><td>0.07</td><td>0.08</td><td>0.08</td><td>0.07</td><td>0.07</td><td>0.03</td><td>0.02</td><td>0.03</td></tr><tr><td>K</td><td>1.66</td><td>1.65</td><td>1.66</td><td>1.67</td><td>1.64</td><td>1.57</td><td>1.54</td><td>1.47</td><td>1.52</td><td>1.86</td><td>1.74</td><td>1.87</td></tr><tr><td>Rb</td><td>0.11</td><td>0.11</td><td>0.10</td><td>0.12</td><td>0.17</td><td>0.09</td><td>0.21</td><td>0.25</td><td>0.22</td><td>0.02</td><td>0.04</td><td>0.04</td></tr><tr><td>Cs</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.03</td><td>0.00</td><td>0.07</td><td>0.07</td><td>0.06</td><td>0.00</td><td>0.00</td><td>0.00</td></tr><tr><td>Li (LA-ICP)</td><td>2.98</td><td>2.99</td><td>2.95</td><td>3.22</td><td>3.24</td><td>3.03</td><td>3.18</td><td>3.23</td><td>3.33</td><td>0.00</td><td>0.01</td><td>0.01</td></tr><tr><td>P</td><td>0.02</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.01</td><td>0.00</td><td>0.01</td><td>0.00</td><td>0.00</td><td>0.00</td><td>0.01</td></tr><tr><td>F</td><td>1.25</td><td>1.26</td><td>1.24</td><td>1.37</td><td>1.35</td><td>1.53</td><td>1.43</td><td>1.47</td><td>1.47</td><td>0.12</td><td>0.02</td><td>0.03</td></tr><tr><td>Fe + Mg + Mn</td><td>1.01</td><td>1.02</td><td>0.96</td><td>0.08</td><td>0.05</td><td>0.08</td><td>0.25</td><td>0.70</td><td>0.13</td><td>0.04</td><td>0.04</td><td>0.07</td></tr><tr><td>Mg-Li</td><td>-2.91</td><td>-2.92</td><td>-2.89</td><td>-3.21</td><td>-3.24</td><td>-3.02</td><td>-3.17</td><td>-3.22</td><td>-3.33</td><td>0.01</td><td>0.00</td><td>0.00</td></tr><tr><td>Fe + Mn + Ti-Al6</td><td>-0.55</td><td>-0.54</td><td>-0.64</td><td>-1.78</td><td>-1.81</td><td>-1.76</td><td>-1.51</td><td>-1.71</td><td>-1.55</td><td>-3.95</td><td>-3.94</td><td>-3.85</td></tr></tbody></table>