Loïs Monnier

Stefano Salvi
email: stefano.salvi@get.omp.eu

Victor Jourdan

Souleymane Sall

Laurent Bailly

Jérémie Melleton

Didier Béziat

Contrasting fluid behavior during two styles of greisen alteration leading to distinct wolframite mineralizations: the Echassières district (Massif Central, France)

Highlights

 Fluid cooling, without evidence of sharp pressure variations, is the main cause for one wolframite mineralization episode.

 Fluid flashing (vaporization), triggered by fracture-induced pressure drops, initiated crystallization of a second type of wolframite mineralization.

 Greisenization of the Beauvoir granite is a continuous process (ca. 400°C down to 190°C), occurring at high temperature as pervasive alteration of the granite body, while at lower temperature it is localized to a vein system.

 Globally, greisen-forming fluids have a strong potential for transporting and precipitating W.

2

 In greisen systems worldwide, regional veins distal to the altered causative magmatic body can be mineralized by greisen-forming fluids.

Introduction

An important proportion of felsic igneous bodies emplaced in the upper part of the crust, particularly the more evolved, rare-metal enriched, and/or peraluminous varieties, exhibits greisen alteration to some extent. Greisenization is characterized by replacement of igneous minerals by various proportions of muscovite, quartz and topaz (Štemprok, 1987), ± tourmaline, apatite, HFSE-bearing minerals, to mention the most common [START_REF] Pirajno | Intrusion-related hydrothermal mineral systems[END_REF]. It is well established that greisen alteration is caused by magmatic-related, acidic fluids that trapped fluid inclusions (FI) showing a wide range of homogenization temperatures (Th; 200 to 450°C; e.g., [START_REF] Burt | Acidity-salinity diagrams; application to greisen and porphyry deposits[END_REF][START_REF] Štemprok | Greisenization (a review)[END_REF][START_REF] Halter | Modeling fluid-rock interaction during greisenization at the East Kemptville tin deposit: implications for mineralization[END_REF][START_REF] Cui | Genesis of the Xiaolonghe quartz vein type Sn deposit, SW China: Insights from cathodoluminescence textures and trace elements of quartz, fluid inclusions, and oxygen isotopes[END_REF], and, in the case of rare metal granites, low salinity (<10 wt.% NaCl eq.; Charoy, 1981 ;[START_REF] Cuney | The Beauvoir topaz-lepidolite albite granite (Massif Central, France); the disseminated magmatic Sn-Li-Ta-Nb-Be mineralization[END_REF][START_REF] Dobeš | Fluid inclusion planes and paleofluid records in the Podlesí granite, Krušné hory Mts[END_REF]Breiter et al., 2017a). Similarly, FI associated with W-Sn ore deposits display for the most part low salinity and range in homogenization temperature from 200 to 400°C (e.g., [START_REF] Naumov | Physicochemical parameters of the formation of hydrothermal deposits: a fluid inclusion study. I. Tin and tungsten deposits[END_REF]. Based on this evidence, as well as on structural, petrographic, geochemical and geochronological data, numerous models propose that the same fluids (with possible local evolution or mixing etc.) that form greisen alteration are also responsible for the formation of the surrounding wolframite (± cassiterite)-bearing stockwork (e.g., [START_REF] Štemprok | Greisenization (a review)[END_REF][START_REF] Pirajno | Intrusion-related hydrothermal mineral systems[END_REF][START_REF] Halter | Modeling fluid-rock interaction during greisenization at the East Kemptville tin deposit: implications for mineralization[END_REF][START_REF] Williamson | Implications from inclusions in topaz for greisenisation and mineralisation in the Hensbarrow topaz granite, Cornwall, England[END_REF][START_REF] Yokart | Late-stage alteration and tintungsten mineralization in the Khuntan Batholith, northern Thailand[END_REF][START_REF] Mao | Geology and molybdenite Re-Os age of the Dahutang granite-related veinlets-disseminated tungsten ore field in the Jiangxin Province, China[END_REF][START_REF] Zhao | Genetic types, mineralization styles, and geodynamic settings of Mesozoic tungsten deposits in South China[END_REF][START_REF] Korges | Depressurization and boiling of a single magmatic fluid as a mechanism for tin-tungsten deposit formation[END_REF][START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF]2019;[START_REF] Zheng | topaz vein. g: population B of recrystallized quartz in stockwork. h: L-rich core of disseminated greisen quartz i: greisen apatite a. j: topaz vein in stockwork enclave of Unit 3[END_REF][START_REF] Chen | The Genetic Association between Quartz Vein-and Greisen-Type Mineralization at the Maoping W-Sn Deposit, Southern Jiangxi, China: Insights from Zircon and Cassiterite U-Pb Ages and Cassiterite Trace Element Composition[END_REF]. A remaining challenge to the understanding of greisen-related wolframite mineralization are the different factors controlling wolframite precipitation, particularly its location, i.e., in quartz veins that are quasi systematically in the host rock and not in the greisenized granite.

To provide an answer to this question, numerous studies have nourished a recent debate on W transport/deposition mechanisms. [START_REF] Lecumberri-Sanchez | Fluid-rock interaction is decisive for the formation of tungsten deposits[END_REF] suggest alteration of the host rock as a key factor for providing the Fe and Mn necessary for wolframite ((Fe,Mn)WO 4 ) precipitation. However, [START_REF] Heinrich | The chemistry of hydrothermal tin (-tungsten) ore deposition[END_REF] and [START_REF] Yang | Metal source and wolframite precipitation process at the Xihuashan tungsten deposit, South China: Insights from mineralogy, fluid inclusion and stable isotope[END_REF] argue that orthomagmatic fluids contain sufficient Fe and Mn to permit wolframite precipitation. This affirmation is verified by LA-ICP-MS analyses of magmatic-related FI, which record high amounts of Fe and Mn, in addition to W [START_REF] Audétat | Formation of a magmatic-hydrothermal ore deposit: Insights with LA-ICP-MS analysis of fluid inclusions[END_REF][START_REF] Harlaux | Geochemical signature of magmatic-hydrothermal fluids exsolved from the Beauvoir Rare-Metal Granite (Massif Central, France): insights from LA-ICPMS analysis of primary fluid inclusions[END_REF][START_REF] Yang | Metal source and wolframite precipitation process at the Xihuashan tungsten deposit, South China: Insights from mineralogy, fluid inclusion and stable isotope[END_REF]. [START_REF] Yokart | Late-stage alteration and tintungsten mineralization in the Khuntan Batholith, northern Thailand[END_REF], [START_REF] Legros | Multiple fluids involved in granite-related W-Sn deposits from the world-class Jiangxi province (China)[END_REF] and [START_REF] Liu | Chemical responses to hydraulic fracturing and wolframite precipitation in the vein-type tungsten deposits of southern China[END_REF] propose mixing between orthomagmatic and meteoric fluids as the cause for wolframite deposition, while [START_REF] Pan | Comparison of fluid processes in coexisting wolframite and quartz from a giant vein-type tungsten deposit, South China: Insights from detailed petrography and LA-ICP-MS analysis of fluid inclusions[END_REF] suggest an input of sedimentary fluids as instrumental in precipitating wolframite. Based on microthermometric data, [START_REF] Korges | Depressurization and boiling of a single magmatic fluid as a mechanism for tin-tungsten deposit formation[END_REF] and [START_REF] Jiang | Fluid inclusion and isotopic (C, H, O, S and Pb) constraints on the origin of late Mesozoic vein-type W mineralization in northern Guangdong, South China[END_REF] propose that depressurization, triggering boiling of the fluid, is the main factor for formation of greisen alteration and simultaneous wolframite-bearing veins. On the other hand, Ni et al. (2015a), [START_REF] Li | Fluid inclusion characteristics as an indicator for tungsten mineralization in the Mesozoic Yaogangxian tungsten deposit, central Nanling district, South China[END_REF] and [START_REF] Chen | The link between fluid evolution and vertical zonation at the Maoping tungsten deposit, Southern Jiangxi, China: Fluid inclusion and stable isotope evidence[END_REF] suggest that simple cooling during fluid transport is sufficient to induce wolframite precipitation. The experimental data of [START_REF] Wood | The hydrothermal geochemistry of tungsten in granitoid environments: I. Relative solubilities of ferberite and scheelite as a function of T, P, pH, and m NaCl[END_REF] confirm that, given a sufficient W concentration in the fluid, cooling and depressurization can control wolframite precipitation, as also proposed by [START_REF] Yang | Metal source and wolframite precipitation process at the Xihuashan tungsten deposit, South China: Insights from mineralogy, fluid inclusion and stable isotope[END_REF] to explain wolframite precipitation as an infill along fractures. [START_REF] Liu | Chemical responses to hydraulic fracturing and wolframite precipitation in the vein-type tungsten deposits of southern China[END_REF], based on numerical modelling, confirm the important role of repeated depressurization episodes, caused by cyclic fracturing. Concerning the fluid chemistry, Wang et al. (2019a) and [START_REF] Wang | In situ Raman spectroscopic investigation of the hydrothermal speciation of tungsten: Implications for the oreforming process[END_REF] show, respectively, that salinity and CO 2 have only a minor impact on W mobility, whereas the role of pH seems critical (see also [START_REF] Wood | The hydrothermal geochemistry of tungsten in granitoid environments: I. Relative solubilities of ferberite and scheelite as a function of T, P, pH, and m NaCl[END_REF], notably the pH increase during interaction with graphite-rich schist host rock [START_REF] O'reilly | Fluid inclusion study of the Ballinglen W-Sn-sulphide mineralization, SE Ireland[END_REF].

The Echassières district in central France is well suited to investigate the role that different parameters might play on the origin of W mineralization. In this area, most of the W is in the form of three wolframite generations related to three distinct hydrothermal events, separated in time [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF]. The earliest W episode occurred in the form of wolframite a, outcropping in a stockwork vein system. The bulk of the W stock consists of a wolframite generation that precipitated during a topazification event (wolframite b), attributed to percolation of a F-rich greisenizing fluid. A last major mineralization event (wolframite c) took place during OH-rich greisen alteration following emplacement of the highly evolved Beauvoir granite. However, occurrence of wolframite c is uneven; it is never found in greisenized granite, but occurs in large amounts in a swarm of mineralized greisen-related quartz veins emplaced in the vicinity of the granite. Interestingly, other veins that are interpreted to have the same origin are barren [START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF]. A previous study ruled out a possible effect of contrasting composition of the greisen-forming fluid between granite and veins to explain this peculiar mode of occurrence [START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF]. The mineral paragenesis of these two wolframite generations suggest similar fluid properties (low-CO 2 , strong acidity and low salinity; [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF], indicative of greisen affinity (Štemprok, 1987).

Here, we report the results of a FI microthermometric study and investigate the role that two intensive physical parameters, pressure and temperature, may have played on these mineralizations.

This study presents an important data collection of FI microthermometric features (more than 800 measures) in the Echassières district, and highlights the opposite behavior of fluids at the origin of wolframite b and c. At a global scale, this work clearly evidences two physical constraints on wolframite mineralization, and provides critical information on the greisen alteration processes.

In addition to W, in contrast with other well-known Variscan W districts in Europe (e.g., Panasqueira district: [START_REF] Noronha | Characterization and timing of the different types of fluids present in the barren and ore-veins of the W-Sn deposit of Panasqueira, Central Portugal[END_REF]Erzgebirge mountains: Breiter, 2012;Cornwall district: Campbell and Panter, 1990) it is possible that greisen alteration of the Beauvoir granite may be linked to distal Sb mineralization in the Nades area. A similar metal association is commonly reported in some W deposits in China [START_REF] Hu | The giant South China Mesozoic low-temperature metallogenic domain: Reviews and a new geodynamic model[END_REF][START_REF] Wang | Regional metallogeny of Tungsten-tin-polymetallic deposits in Nanling region, South China[END_REF]. This genetic relationship is supported by quartz trace element composition (very similar signatures and high Sb content for quartz from greisen and Nades vein; [START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF], notably the Sb content in greisen quartz which is >1 ppm with median value equal to ca. 5 ppm, corresponding only to quartz associated to Sb mineralization according to data from literature [START_REF] Rusk | Visualizing trace element distribution in quartz using cathodoluminescence, electron microprobe, and laser ablation-inductively coupled plasma-mass spectrometry[END_REF][START_REF] Pacák | Trace-element chemistry of barren and ore-bearing quartz of selected Au, Au-Ag and Sb-Au deposits from the Bohemian Massif[END_REF]. In this work, the characteristics of the fluids associated with the stibnite-quartz veins cropping out at the south of Beauvoir granite will be also discussed.

Regional geology

Located in the northern part of the French Massif Central (Fig. 1), the Echassières district is hosted by the Sioule metamorphic series. The district is bounded by the crustal-scale strike-slip Sillon Houiller fault on the west, by the Saint-Gervais granite and a formation known as anthracite tuff on the south, while the Tréban granite and Cenozoic sediments limit it on the North and East, respectively. The Sioule series consists of three metamorphic units which form an inverted metamorphic sequence structured in two major antiforms. Two granitic systems, the Beauvoir/Colettes plutonic pair and Pouzol-Servant laccolith intrude the deeper para-autochtonous unit of the series, respectively, in the northern and southern antiform (Fig. 1). The Sioule series records mostly the peak of barrovian metamorphism (ca. 600°C and 7 kbar for the para-autochtonous unit; [START_REF] Schulz | PT-paths from metapelite garnet zonations, and crustal stacking in the Variscan inverted metamorphic sequence of La Sioule, French Massif Central[END_REF][START_REF] Schulz | EMP-monazite age controls on PT paths of garnet metapelites in the Variscan inverted metamorphic sequence of La Sioule, French Massif Central[END_REF] occurring at ca. 360 Ma [START_REF] Couto | Monazite U-Th-Pb EPMA and zircon U-Pb SIMS chronological constraints on the tectonic, metamorphic, and thermal events in the inner part of the Variscan orogen, example from the Sioule series, French Massif Central[END_REF]. It is intruded by the Pouzol-Servant laccolith (ca. 330 Ma;[START_REF] Pin | Sr-Nd isotopic study of igneous and metasedimentary enclaves in some Hercynian granitoids from the Massif Central, France[END_REF], during the Visean peak of peraluminous magmatic activity, also recorded by the resetting of the 40 Ar/ 39 Ar systematics in metamorphic micas (ca. 333 Ma, Faure et al., 2002;[START_REF] Couto | Monazite U-Th-Pb EPMA and zircon U-Pb SIMS chronological constraints on the tectonic, metamorphic, and thermal events in the inner part of the Variscan orogen, example from the Sioule series, French Massif Central[END_REF], caused by associated hydrothermal activity. The Beauvoir/Colettes granitic system was emplaced in the series during the late extensional orogenic stage of the Variscan belt (ca. 310 Ma; [START_REF] Duthou | Etude isotopique Rb-Sr de l'apex granitique d'Echassières (Granite des Colettes, granite de Beauvoir)[END_REF][START_REF] Cheilletz | Ages 40Ar/39Ar du leucogranite à topaze-lépidolite de Beauvoir et des pegmatites sodolithiques de Chédeville (Nord du Massif Central, France). Signification pétrologique et géodynamique[END_REF][START_REF] Melleton | Rare-elements (Li-Be-Ta-Sn-Nb) magmatism in the European Variscan belt, a review[END_REF].

Mineralization events

The Echassières district is a remarkable site involving a complex sequence of events, many of which mineralized mainly in Sn, W, Sb, Li, Nb-Ta. The earliest occurrence is the La Bosse stockwork (Fig. 1.A-B), a swarm of sub-horizontal quartz veins emplaced contemporaneously to multiple aplitic dykes before regional metamorphism. The stockwork veins contain minor wolframite (ferberite/hubnerite ratio ≈ 8.4; calculated using atomic proportions in [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF], commonly altered, referred to as "wolframite type a". However, it was impossible to identify primary fluid inclusions linked to its formation, notably due to extensive quartz recrystallization during metamorphism, and percolation of several subsequent generations of fluids. Therefore, this generation was not considered further in this study.

After metamorphism, during the Visean magmatism, a series of topaz veins crosscut the stockwork and the surrounding schist, locally replacing partially dissolved quartz veins. This topazification event was accompanied by pervasive F-rich alteration (topaz ± F-Li-rich micas; first greisen event) and precipitation of abundant wolframite (type b; ferberite/hubnerite ratio ≈ 3.5) and lower amounts of cassiterite in the quartz and the topaz veins as well as in the schist.

Followed the emplacement of the Beauvoir/Colettes granitic system (Fig. 1), during the Stephanian.

Colettes, the larger body, is a porphyritic two-micas granite while Beauvoir is a highly-evolved albitelepidolite-topaz equigranular granite, well known for its rare-metal content, rich in cassiterite, colombo-tantalite and pyrochlore [START_REF] Aubert | Les coupoles granitiques de Montebras et d'Échassières:(Massif Central français) et la genèse de leurs minéralisations en étain, lithium, tungstène et béryllium[END_REF][START_REF] Wang | Mineraux dissemines comme indicateurs du caractere pegmatitique du granite de Beauvoir, Massif d'Echassieres, Allier, France[END_REF]. The apical part of the Beauvoir granite shows remarkable enrichment in high-field strength elements (HFSE; ca. 50 ppm of W, 100 ppm of Nb, 150 ppm of Ta, and up to 1000 ppm of Sn), although Zr and Hf are strongly depleted [START_REF] Raimbault | Geochemical evidence for a multistage magmatic genesis of Ta-Sn-Li mineralization in the granite at Beauvoir, French Massif Central[END_REF]. In addition to Li, lepidolite is also enriched in Rb and F. Niobium and Ta are concentrated in columbo-tantalite group minerals, Sn in cassiterite, and pyrochlore-group minerals contain important quantities of U, Nb, Ta, W (Fonteille, 1987;[START_REF] Cuney | The Beauvoir topaz-lepidolite albite granite (Massif Central, France); the disseminated magmatic Sn-Li-Ta-Nb-Be mineralization[END_REF][START_REF] Wang | Mineraux dissemines comme indicateurs du caractere pegmatitique du granite de Beauvoir, Massif d'Echassieres, Allier, France[END_REF].

The Beauvoir granite (in particular its apex) exhibits an important greisen alteration (Fig. 1.B) second greisen event) consisting of replacement of igneous minerals by muscovite, quartz and apatite. At Beauvoir, greisen alteration is not accompanied by rare-metal mineralization, and igneous cassiterite is replaced by muscovite. However, in the host rocks next to the Beauvoir granite, cassiterite precipitated together with topaz , during reactivation of the topaz veins formed during topazification. This superimposed greisen alteration also caused minor cassiterite, colombo-tantalite and wolframite (type c; hubnerite/ferberite ratio ≈ 0.3) precipitation in quartz veins in the vicinity of the Colettes and Beauvoir granites (Fig. 1.A; known as 'proximal veins'; [START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF], with the exception of the Mazet veins, where wolframite c is very abundant. More distal from this intrusive system, occurs a set of quartz veins, characterized by the presence of sulphides. One of these occurrences consists of the Nades stibnite veins, interpreted to have derived from the greisen fluids [START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF].

The last hydrothermal episode consists of late-stage kaolinization of the Beauvoir and Colettes granites, mostly overprinting the greisen alteration [START_REF] Charoy | Evidence of Sr mobility in and around the albite-lepidolite-topaz granite of Beauvoir (France): an in-situ ion and electron probe study of secondary Sr-rich phosphates[END_REF]. Wolframite was also altered, commonly replaced by W-rich goethite. Some mineralized occurrences in the Echassières district, e.g., Sb veins of Pouzol-Servant granite and Cu-Sn sulphide veins of the Chaillat locality, remain poorly genetically constrained.

Sampling and analytical methods

Most of the samples used in this study were collected in the field, from the Beauvoir open pit, Colettes granite, and in the Suchot area (near the town of Echassières, France; Fig. 1). In addition, several samples, representative of the different facies at depth, were taken from the GPF (Deep Geology of France) drill-hole series collection (hole # 1) (Orléans, France). Finally, samples from the Mazet wolframite mineralization were obtained from the French Geological Survey (BRGM, Orléans, France) collection, because the mine site has since been rehabilitated and does not crop out any longer.

The mineralogy and textural relationships were investigated using optical microscopy. Fluid inclusion studies of quartz and topaz were done using double-polished 0.2 mm-thick wafers.

Microthermometric measurements were carried out using a Linkam THMGS 600 heating-freezing stage, mounted on an Olympus BX-51 microscope. Measurements were performed at the GET laboratory, following the procedures outlined by [START_REF] Roedder | Fluid inclusions[END_REF] and [START_REF] Shepherd | A practical guide to fluid inclusion studies[END_REF]. The stage was calibrated against pure H 2 O synthetic inclusions (0 and 374.1°C), supplied by SynFlinc, and pure CO 2 -bearing natural inclusions (-56.6°C) from Camperio (Ticino, Switzerland). Measurements near and below 0°C are accurate to 0.1°C and to 1°C at higher temperatures. Heating rates were 0.2°C/min when phase transitions were approached. Cryogenic experiments were carried out before heating experiments to avoid the risk of inclusions decrepitating. Salinity (S) of fluid inclusions, expressed as wt.% eq. NaCl, was calculated based on the temperature of final ice melting (T m ) and the equation of [START_REF] Bodnar | Revised equation and table for determining the freezing point depression of H2O-NaCl solutions[END_REF] (S = -1.78 T m + 0.0442 T m 2 + 0.000557 T m 3

). It has been suggested that primary FI commonly occur as individual isolation or groups along growth zones of quartz or healed micro-fractures, whereas secondary FI tend to occur in trails and go through quartz grain boundaries [START_REF] Goldstein | Fluid inclusion microthermometry[END_REF]. However, using the above criteria classifying fluid inclusions is not always feasible because the crystal growth banding in quartz cannot be always observed in these three deposits. Therefore, apart from the typical primary FI along quartz growth zones, other FI data on quartz in this study were obtained from isolated FI that might be primary in origin according to [START_REF] Roedder | Fluid inclusions[END_REF] or FI assemblages which have similar heating-freezing behavior [START_REF] Fall | How Precisely Can the Temperature of a Fluid Event be Constrained Using Fluid Inclusions?[END_REF]; and references therein).

Fluid inclusion petrography

A detailed description of magmatic and hydrothermal rocks of the Echassières district is available in [START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF] and [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF]. Consequently, we focus on some aspects of mineralogy and textural relationships that bear an impact on the petrography of fluid inclusions.

Unfortunately, identification of FI population coeval with wolframite a crystallization, and more globally contemporaneous of the formation of quartz veins of the La Bosse stockwork is impossible, considering the reset triggered by regional metamorphism and the subsequent hydrothermal episodes (topazification, greisenization, and kaolinization) which affected the stockwork [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF].

Beauvoir area

Greisen in the Beauvoir granite

Greisen alteration is particularly strong at the apex of the Beauvoir granite (Fig. 2.A), where it is expressed by pervasive replacement of magmatic minerals (feldspars ± lepidolite and quartz) by hydrothermal quartz, muscovite ± apatite (Fig. 2.C), and formation of subvertical quartz vein (Fig. 2.A). Newly formed, disseminated quartz crystals are euhedral, contrarily to primary igneous quartz which is commonly partly dissolved. Large greisen quartz crystals display, in their median part, a characteristic growth band marked by the presence of FI (Fig. 2.E). These FI have irregular shapes, vary in size from <1 to ca. 20 µm and are mostly composed of a vapor (V) phase (Fig. 2.F). In the core of these crystals, surrounded by the V-rich FI band, there is a population of liquid-vapor (L-V) FI, 3 to 4 µm in size, consisting of 70 % liquid (L), of oval to rectangular shape. On the outer part of the V-rich FI band, the rim of these quartz crystals contains disseminated FI that are similar to those found in the quartz core but with higher proportions of L, i.e. ca. 80 % by volume. These three populations of FI are considered as primary, as they are each restrained to a different growth zones. Greisen-related quartz veins within the Beauvoir granite are composed of euhedral cm-sized crystal (Fig. 2.B). A wellmarked growth zoning is developed in these crystals, highlighted by a succession of alternating FIrich and FI-poor bands (Fig. 2.D). FI display irregular shapes and variable liquid/vapor ratios (Fig. 2.G).

These FI are very small (rarely > 3µm) and only a few FI of relatively larger size (~5 µm) were monitored. The rare FI observed in the FI-poor bands display homogeneous liquid/vapor ratio, equal to ca. 90 %.

La Bosse stockwork -Quartz veins

Quartz veins of La Bosse stockwork are subhorizontal, commonly 10 to 20 cm wide (Fig. 3.A), and contain topaz, wolframite and rare cassiterite and colombo-tantalite. Given that several metamorphic and hydrothermal episodes were superposed to the La Bosse stockwork mineralization, we are unable to discern FI potentially contemporaneous to its formation. The oldest FI population that could be clearly identified is the one synchronous to the topazification episode that affected the stockwork after its formation (and before the Barrovian regional metamorphism). Topaz I, common throughout the whole stockwork (Fig. 3.C), contains abundant FI forming a single population, consistently so in each topaz crystal studied. These FI contain a liquid phase filling ca. 50 to 60 % of the inclusion volume (Fig. and contains a homogeneous FI population of regular shape, small size (few µm), with L filling ca. 50-60 % of the total volume.

-Stockwork enclave in the Beauvoir granite A particularly interesting sample was collected from a drill core from the Beauvoir granite that intersected an enclave of the La Bosse stockwork consisting of a stockwork vein with its host schist.

This sample records all of the hydrothermal episodes related to wolframite crystallization in the Echassières district [START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF]2019).

The stockwork episode is expressed by quartz and wolframite a, the topazification episode by topaz I and wolframite b, and the Beauvoir greisen event by blue apatite and wolframite c ( In some instances, grains of apatite show textural evidence of coprecipitation and apatite with wolframite c (cf. Fig. 4.G in Monnier et al., 2019). Fluid inclusions in Beauvoir greisen quartz and apatite are L-rich (70 to 80 % L); those in quartz show regular to rounded shapes, while those in apatite are systematically elongated parallel to the C axis.

Regional veins

Proximal veins

Proximal veins form a network of subvertical quartz veins located in the vicinity or within the Colettes/Beauvoir granitic complex (Fig. 1).

-The Suchot vein

The Suchot vein measures from 1 to 2 m in width (Fig. 6.A), and consist essentially of two quartz generations, plus minor muscovite and cassiterite. The vein selvages contain quartz and muscovite, similarly to the Beauvoir greisen. In the vein, the first quartz generation is euhedral, up to cm in size, with growth zones exhibiting sequential FI poor and FI rich areas (Fig. 6. B). Differently than for the quartz veins at the interior of the Beauvoir granite, FI in these growth zones show homogeneous L/V ratios, with L comprising ca. 80 % of total FI volume (Fig. 6.C). FI in the second quartz generation are aligned along the direction of the quartz fibers (Fig. 6.B), and display variable L/V volume ratios (Fig.

6.D)

.

-Mazet veins

Quartz veins at Mazet share several characteristics with the Suchot vein, i.e., geometry (metric in width, subvertical, oriented N/S), presence of two quartz generations. Also similar to that at Suchot, the first quartz generation is euhedral and cm-sized, whereas the second quartz generation presents a not-well crystallized, micro-quartz texture (post-recrystallized H 2 O-rich colloform silica). The microquartz is accompanied by important quantity of wolframite c (Fig. 6.E). As in quartz from Suchot vein, FI located in growth zones of the first quartz generation are L-rich (ca. 80 %; Fig. 6.F). On the other hand, in the rare parts of the second quartz generation where FI could be observed, these display globular shapes and contain only a V phase (Fig. 6.E).

Sb-bearing quartz veins -Nades vein

At the Nades locality, a large quartz vein consisting of a meter-sized main body and interconnected cm-to mm-sized satellite veinlets (Fig. -Capitraux and Cros veins

In both localities occur a quartz vein of some 20 cm in width, displaying the same unusual feature, i.e., a radial quartz texture, called "star quartz" in this study, initiated around a small ferrous oxide nuclei. The star quartz crystals, roughly spherical, are about 5 mm in diameter, uncommonly up to 2 cm (Fig. 7.E). Sealing of these veins are commonly incomplete, and they can exhibit a strong porosity (up to 50 %). Stibnite occurs in variable amount, and is found mainly filling the porosity between star quartz crystals (Fig. 7.C,E) and, in lesser proportions, as disseminated tiny acicular crystals within the outer rims of quartz. FI are very rare in the core of star quartz, whereas the rims contain clusters of FI, accompanying the stibnite (Fig. 7.F). These FI are generally regular, ca. 5 µm in width, and contain ca. 95 % L.

To resume, the FI populations described in the above paragraphs can be grouped into two main groups, based on careful FI petrography and associated hydrothermal alteration parageneses. These correspond to the two main hydrothermal episodes that affected these rocks, after metamorphism, and that were at the origin of the two W mineralization events: 1) A first greisen-forming fluid, which

Microthermometric results

For each FI type investigated in this study, several occurrences of any given FI assemblage were measured from different crystals, to confirm the data repeatability, unless otherwise specified. FI that could be related petrographically to the topazification episode, whether in topaz I or in stockwork quartz, form a rather homogeneous population, whereas the fluid associated with formation of the OH-greisen is recorded in a wide variety of FI types in different hydrothermal minerals. None of the IF monitored in this study show solid phases. Similarly, ice was the only phase that formed upon cooling, confirming the relative low concentration of gases such as CO 2 . During the heating process, all L-rich and V-rich FI homogenized, respectively, to the liquid and vapor phases.

For FI assemblages showing heterogeneous trapping of the L and V phases, only those displaying the lowest vapor/liquid ratios were retained for monitoring.

Descriptive statistics of microthermometric data for each FI population are summarized in Table 1.

Equivalent salinity and homogenization temperature median values, plus sketches depicting the petrography and the locality of the studied FI populations, are given in Figures 8910.

Salinities

During sub-zero heating runs the first occurrence of ice melting was recorded to obtain an estimate of the eutectic point of the system (T e ). For all FI belonging to the topazification episode the firstmelting, when observed, occurred at temperatures just above or equal to -72°C (Fig. 4.F). Such low values suggest that Li was likely an important component in the fluid [START_REF] Monnin | Thermodynamics of the LiCl+ H2O system[END_REF][START_REF] Dubois | Investigation of the H2O-NaCl-LiCl System: A Synthetic Fluid Inclusion Study and Thermodynamic Modeling from-50° to+ 100° C and up to 12 mol/kg[END_REF]. Determination of eutectic temperature for the greisen fluid was challenging, as this phase transition was difficult to observe due to the small size of most FI and to their low salinities (see below). However, by applying the cycling technique described by [START_REF] Reynolds | Short Course on Fluid Inclusions[END_REF], we could record a sufficient number of measurements, which approached and were never lower than -21°C. These measurements were confirmed by the occurrence of a few larger FI where a first melting at -21°C could be observed. Such figure is consistent with NaCl dominating other salt species in the fluid (T e of the H 2 O-NaCl system is -21.1°C; [START_REF] Bodnar | Revised equation and table for determining the freezing point depression of H2O-NaCl solutions[END_REF]. Nevertheless, these results are indicative, and it is possible that other salts were present in addition to Na, particularly cations such as K + and Mg 2+ , given that their presence does not change significantly the eutectic temperature. The presence of Li + in the topazification fluid is not surprising, as lepidolite is a common alteration mineral, whereas the alteration paragenesis in the greisen is dominated by the presence of muscovite and quartz. The temperature of final ice melting ranged from -10 to 0°C for all FI from both alteration episodes, with a great majority of data above -4°C. These data indicate relatively low salinities, with 99% of values < 10 wt.% NaCl eq. and the majority of values < 4 wt.% NaCl eq. However, a weak trend toward somewhat higher salinities can be distinguished for the greisen fluid, moving away from the Beauvoir granite, e.g. the median salinity is 1 wt.% NaCl eq. for greisen in the granite, while it is 5 wt.% NaCl eq. for quartz from Nades and Suchot veins (Quartz 1).

Homogenization Temperatures (Th)

All T h values, for each FI population, are detailed in the histograms depicted in Figure 11. FI trapped during the topazification episode record a very narrow range of T h , comprised between 370 and 395°C (Fig. 11.A,F,H,I,J,M), except for a small peak at 250-270°C. The latter range, however, is well marked for some FI assemblages in topaz I from the polyphased topaz vein and in recrystallized quartz in the La Bosse stockwork (Figs.

Discussion

P-T conditions

Most FI populations described above display homogeneous vapor/liquid ratio suggesting trapping of a supercritical fluid. For these populations, T h represents the minimal estimate for the trapping conditions. In some instances, the occurrence of coexisting L-rich and V-rich FI within the same assemblage (e.g., group or growth zone; Fig. 2.F,G; Fig. 6.D) such as observed in greisen veins within the Beauvoir granite and in Suchot vein quartz, indicates local boiling conditions. In this case, we used the homogenization temperatures of the vapor-and liquid-rich end-members to estimate the actual trapping temperature.

Because we do not have independent means for constraining the temperature or pressure of the system, we can assume that the trapping conditions lie along an isochoric path defined by the physical properties of the fluid inclusions, confined to conditions given by a reasonable geothermal gradient for this system. If we consider a common average crust geothermal gradient (ca. 30°C/km), the intersections with some isochores of Beauvoir greisen and topazification FI occur at unrealistically elevated temperatures (more than 600°C and 1000°C, respectively; Fig. 12.A). Given the presence of crystallizing intrusions, we suggest a gradient for our system at about 150°C/km (Fig.

12.A). Using this gradient, we obtain trapping conditions that fall within the range for FI populations related to greisen alteration and wolframite mineralization described in the literature (e.g., [START_REF] Williamson | Implications from inclusions in topaz for greisenisation and mineralisation in the Hensbarrow topaz granite, Cornwall, England[END_REF][START_REF] Naumov | Physicochemical parameters of the formation of hydrothermal deposits: a fluid inclusion study. I. Tin and tungsten deposits[END_REF][START_REF] Cui | Genesis of the Xiaolonghe quartz vein type Sn deposit, SW China: Insights from cathodoluminescence textures and trace elements of quartz, fluid inclusions, and oxygen isotopes[END_REF][START_REF] Jiang | Fluid inclusion and isotopic (C, H, O, S and Pb) constraints on the origin of late Mesozoic vein-type W mineralization in northern Guangdong, South China[END_REF]. Such conditions are coherent with the emplacement of a hot granitic magma body at shallow depth, the Beauvoir granite, proposed to have occurred at ca. 3 km according to [START_REF] Cuney | The Beauvoir topaz-lepidolite albite granite (Massif Central, France); the disseminated magmatic Sn-Li-Ta-Nb-Be mineralization[END_REF] based on stable isotopic systematics on mineral pairs and on microthermometric results on orthomagmatic FI), and suggest that circulation of at least the Beauvoir greisenizing fluid took place before the granite cooled substantially. This gradient is also consistent with the elevated T h of the FI related to topazification, which suggests that this fluid also originated from a shallow magmatic source, even though such magmatic body does not crop out at the present surface in the Echassières district.

While the FI homogenization data for the topazification episode show a very well-defined peak, bracketing the conditions of the topazification fluid to a narrow range (Fig.

Main differences in fluid behavior during deposition of the two types of wolframite

For a geothermal gradient of 150°C/km, wolframite b crystallized in a temperature range between ca.

400 to 550°C while wolframite c from Mazet vein crystallized between ca. 250 to 260°C.

Crystallization temperature of wolframite c in the stockwork was apparently more elevated, as indicated by high homogenization temperatures measured in FI from contemporaneous apatite (ca.

350°C; apatite a in Fig. 11.G). Given the relatively large temperature difference between wolframite c from stockwork and Mazet, it is remarkable to see a similar chemical composition. This also indicates that the Fe/Mn ratio variations in wolframite c are apparently not a function of fluid temperature, as recently suggested as a general characteristic [START_REF] Michaud | The H/F ratio as an indicator of contrasted wolframite deposition mechanisms[END_REF].

As mentioned in the previous section, pressure variations induced by fracturing played a key role in wolframite c deposition (Fig. 12.C), whereas FI that trapped the fluids that precipitated wolframite b did not record evidence of boiling. Given that decrease in either pressure and temperature is considered to be an efficient process for destabilizing W complexing in the fluid and triggering wolframite precipitation [START_REF] Wood | The hydrothermal geochemistry of tungsten in granitoid environments: I. Relative solubilities of ferberite and scheelite as a function of T, P, pH, and m NaCl[END_REF], it is likely that, in the absence of fracture-activated pressure drops, simple cooling could have triggered W saturation in the fluid and crystallization of wolframite b, together with topaz I, during the topazification episode.

The salinity values obtained from FI ice melting temperatures for the two greisen generations are generally low, varying from about 0 to 10 wt.% NaCl eq., with most data concentrating between ca. 2 and 5 wt.% (Fig. 13). The variations inherent to the Beauvoir greisen group show a slight increase in median values and in overall range with transport distance from the source, while the fluid that underwent unmixing is characterized by slightly lower values (with the exception of quartz 2 from Suchot vein; median value of 5 wt.%). Most salinity values measured in topaz I from the first greisen episode cluster around 3 wt.%, although the entire data population stretches from 0 to ca. 10 wt.% (Fig. 13). Notably, topaz I from the La Bosse dyke displays uncommonly high salinity median values of 8 wt.% NaCl eq. Considering the similarities of the FI data for all populations, it is not possible to distinguish between the two greisen episodes based on the fluids' ionic concentration.

Trace-element data permit to discriminate the two types of hydrothermal topaz in the La Bosse Stockwork, and to assign them to topazification (topaz I) and Beauvoir greisen alteration (topaz II) [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF]. FI T h data also show separate clusters for the two topaz types, with median values equals to ca. 270 and 380°C, respectively (Fig. 14.A), as well as slightly higher salinities for the topaz-II generation (Fig. 14.B; see also Th vs salinity plot in Supplementary Material). Nonetheless, there is an overlap in some of the data for the two topaz types in the 240-300°C range (Fig. Lithium concentrations in the fluids responsible for the topazification and second greisen formation seem to be significantly different, as suggested by the low eutectic temperature recorded only for FI from the former (near -72°C). The nature of accompanying micas, i.e., F-Li-rich lepidolite to F-rich biotite (unpublished data) for topazification alteration and OH-rich muscovite for the Beauvoir greisen fluid (Fonteille, 1987), suggests that F and Li are enriched in the former case, but depleted in the latter. Hence, topazification, responsible for wolframite b, share several characteristics with the F-Li-rich greisen type (Štemprok, 1987), suggesting it may correspond to an exogreisen, given that it is not observed within a granite. Sericitic alteration of the Beauvoir granite (wolframite c) is, on the other hand, in accordance with the OH-rich greisen type. [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF] demonstrated that it was two different granites that sourced the hydrothermal fluids that led to topazification and Beauvoir greisen alterations. The data presented here confirm the occurrence of two greisen episodes and that they were characterized by different fluid chemistry and evolution, as illustrated by their different P-T paths in Figure 12.

Mineralizing processes

Topazification (wolframite b episode)

Topazification clearly affected the La Bosse stockwork, host to wolframite a (Fig. 15.A,B). As mentioned above, no evidence for boiling was observed in fluid inclusions related to topazification (topaz I), suggesting that the hydrothermal process involved in the concomitant precipitation of wolframite b did not involve changes in pressure. The limited occurrence of topaz veins, in addition to very effective pervasive fluid percolation (i.e., rock permeability) detected in these rocks are consistent with limited pressure fluctuations (Fig. 15.B). This can probably be explained by a high quartz solubility in the HF-rich fluid [START_REF] Ellis | Chemical processes in hydrothermal systems-a review[END_REF][START_REF] Mitra | Solubility and dissolution rate of silica in acid fluoride solutions[END_REF], which created connected porosity inhibiting local fluid overpressure. Dissolution of quartz permitted to focus fluid circulation in the stockwork quartz veins triggering an important concentration of topaz and wolframite b in the vein. Wolframite b, as well as topaz, are also found in albite dykes. Preferential occurrence of W in Mn-Fe-poor rocks (veins and dykes) rather than in the schist suggests that there was no need for fluid interaction with the latter to provide the Fe and Mn needed for wolframite precipitation.

The strong density of FI T h values around 380°C for topaz I could stand to signify a threshold temperature for the topazification episode. As mentioned above, in this case cooling is likely the cause for W saturation and consequent wolframite b crystallization. Another factor that could contribute to decrease wolframite solubility is decreasing of fluid acidity due to fluid-rock interaction [START_REF] Wood | The hydrothermal geochemistry of tungsten in granitoid environments: I. Relative solubilities of ferberite and scheelite as a function of T, P, pH, and m NaCl[END_REF] and massive topaz crystallization (e.g., [START_REF] Halter | The role of greisenization in cassiterite precipitation at the East Kemptville tin deposit[END_REF].

The relatively high temperature of wolframite b crystallization compared to other deposits would mean that the topazification fluid is strongly enriched in W, accordingly to [START_REF] Wang | In situ Raman spectroscopic investigation of the hydrothermal speciation of tungsten: Implications for the oreforming process[END_REF]. Two factors can explain this anomaly. A first one is an uncommon fluid chemistry, more acidic and F-rich than typical fluids at the origin of W deposit; a second one is the potential remobilization of wolframite a of the La Bosse stockwork (cf. [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF], which increased the amount of W in solution. Although wolframite b crystallizes contemporaneously with topaz, the role of fluoride complexing of W in an aqueous phase is still not well understood [START_REF] Wood | The hydrothermal geochemistry of tungsten in granitoid environments: I. Relative solubilities of ferberite and scheelite as a function of T, P, pH, and m NaCl[END_REF].

The source of the topazification fluid also remains not well constrained [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF]. A greisen-like origin after boiling of a previous orthomagmatic fluid should be considered (Fig. salinity remained low (mainly < 5 wt.% NaCl eq.), as already observed in other system (Charoy, 1981;[START_REF] Jiang | Fluid inclusion and isotopic (C, H, O, S and Pb) constraints on the origin of late Mesozoic vein-type W mineralization in northern Guangdong, South China[END_REF].

Surprisingly, greisen alteration at Beauvoir is relatively poor in F and Li, despite the fact that this granite is strongly enriched in these and other rare metals. Nevertheless, the exceptional P content of the fresh granite [START_REF] Raimbault | Geochemical evidence for a multistage magmatic genesis of Ta-Sn-Li mineralization in the granite at Beauvoir, French Massif Central[END_REF] is reflected by the remarkably high abundance of apatite in the greisen. In the Cínovec granite, roughly analogous to Beauvoir [START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF], greisen alteration consists of quartz plus zinnwaldite. The latter is the most F, Li, and rare-metal enriched mica found in these rocks, including igneous varieties. This evidence can be interpreted as indicating an opposite behavior of these elements during greisen alteration of the two granites. At Beauvoir, most of the F and Li are transported by greisen fluids to the surrounding host rocks, as suggested by the low concentrations of these elements found in greisen-altered granite (Merceron et al., 1992;[START_REF] Raimbault | Geochemical evidence for a multistage magmatic genesis of Ta-Sn-Li mineralization in the granite at Beauvoir, French Massif Central[END_REF]. At Cínovec, greisen alteration is mostly confined to the granitic body, retaining these elements as well as ore metals such as Sn and W. We therefore suggest that it is critical to apprehend the extent of mobility of a greisen-forming fluid to understand its role on ore metal transport and deposition (compare with the Cínovec granite: Breiter et al., 2017a;[START_REF] Breiter | Quartz chemistry-a step to understanding magmatichydrothermal processes in ore-bearing granites: Cínovec/Zinnwald Sn-W-Li deposit, Central Europe[END_REF]2017c;2019).

Greisen is developed only in zones displaying enhanced permeability, i.e. the apex and fractured zones in the Beauvoir and Colettes granites, and fractures in the host schist, whereas dykes of Beauvoir granite intruding the schist, or the La Bosse quartz veins, only show limited signs of greisen alteration (they are mostly kaolinized, cf., [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF]. These results contradict a recent fluid inclusion study, which proposes that FI in the stockwork represent the orthomagmatic fluids derived from the Beauvoir granite [START_REF] Harlaux | 40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U-Pb dating of wolframite[END_REF]. However, at the time of their writing, it had not been recognized that the episode of topazification of the La Bosse stockwork predates the emplacement of the Beauvoir granite [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF]. Consequently, we suggest that the fluid inclusions from the La Bosse stockwork studied by [START_REF] Harlaux | Geochemical signature of magmatic-hydrothermal fluids exsolved from the Beauvoir Rare-Metal Granite (Massif Central, France): insights from LA-ICPMS analysis of primary fluid inclusions[END_REF] record the orthomagmatic signature of the magma that sourced the topazification fluid, not that of the Beauvoir granite.

Suchot (barren) vs Mazet (W mineralized) proximal veins

The distribution of wolframite in the proximal veins raises the question as to why wolframite c is massively localized in the Mazet area and not in other proximal veins, e.g., Suchot vein. A marked difference that was observed in these two localities is that fluid flashing (evidenced by micro-quartz texture and presence of a vapor-rich FI population) took place in the Mazet veins, whereas only evidence for boiling could be recognized in FI from the Suchot veins. This distinction in fluid behavior may explain the restriction of wolframite at Mazet. Indeed, during boiling of a fluid, W is known to strongly fractionate into the liquid phase [START_REF] Audétat | Formation of a magmatic-hydrothermal ore deposit: Insights with LA-ICP-MS analysis of fluid inclusions[END_REF][START_REF] Harlaux | Geochemical signature of magmatic-hydrothermal fluids exsolved from the Beauvoir Rare-Metal Granite (Massif Central, France): insights from LA-ICPMS analysis of primary fluid inclusions[END_REF], suggesting that flashing triggered wolframite precipitation by causing vaporization of the totality of the liquid. In case of only limited boiling on the other hand, W could fractionate into the liquid phase without necessarily exceeding its saturation in W, which is likely what happened at Suchot, hence the absence of W mineralization.

Cyclic behavior of Beauvoir greisen fluid

Before fracturing, greisen fluid circulation was restricted to the granite body, because of the low permeability of the surrounding schist and the sealed stockwork system. When regional shear slip constraints [START_REF] Gagny | Contribution de la pétrologie structurale à la connaissance des conditions de mise en place et de structuration complexe du granite des Colettes (Massif d'Echassières, Massif Central Français)[END_REF], coupled with increasing fluid pressure, triggered vertical fracturing (Fig. 16.A), the fluid was immediately connected to the surface. This was a very effective drain, focusing the greisenizing fluid circulation though the proximal quartz veins, and limiting mixing with the host schist , as also indicated by investigation of the quartz chemistry [START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF].

During fracturing, sharp pressure drops drastically lowered mineral solubility in the greisen fluid, triggering massive precipitation of new minerals, such as quartz and muscovite. This rapidly sealed the porosity [START_REF] Moncada | Mineral textures and fluid inclusion petrography of the epithermal Ag-Au deposits at Guanajuato, Mexico: Application to exploration[END_REF]Launey et al., 2019) reducing permeability and increasing fluid pressure, thus initiating a new fracture-seal cycle and wolframite mineralization, all along the cooling path of the fluid (Fig. 12. C and Fig. 16.B;[START_REF] Bons | A review of the formation of tectonic veins and their microstructures[END_REF]. This process is particularly well recorded by the FI populations in the different greisen quartz generations, from which we obtained large variations in Th, and which provide evidence for several boiling/flashing episodes. Possibly, in addition to hydraulic fracturing, seismic activity played a key role in fracturing during greisen alteration, as suggested by the occurrence of a proximal vein transformed to cataclasite (fault core zone) in the Colettes granite [START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF].

On a much smaller scale, one single greisen vein within the Beauvoir granite provided a similar set of evidence for several boiling cycles. Centimeter-size quartz crystals exhibit FI evidence for a succession of boiling episodes (see above; the system becomes open to the surface. A combination of successive boiling (concentrating metals in fluid) with subsequent flashing (initiating the precipitation) appears to be an effective mechanism to form a rare metal deposit (less so for metals with an affinity for the vapor phase, e.g., Cu, cf.

Williams-Jones and [START_REF] Williams-Jones | 100th Anniversary special paper: vapor transport of metals and the formation of magmatic-hydrothermal ore deposits[END_REF].

Stibnite mineralization

The two distal Sb deposits, "Nades veins" in the schist and "Capitraux vein" in the Pouzol Servant granite (Fig. 1

Comparison with other W deposits

As far as we know, there is no equivalent of the entire multistage W mineralization such as occurred in the Echassière district, worldwide. Nevertheless, each mineralizing event can be taken individually as an analogue of other wolframite deposits. An example is the Maoping deposit in China [START_REF] Legros | Multiple fluids involved in granite-related W-Sn deposits from the world-class Jiangxi province (China)[END_REF] where a topazification episode shows similar features to the first (F-rich) greisen episode that affected the La Bosse stockwork, both in terms of mineral assemblage (topaz, Fe-Li-micas, wolframite and cassiterite), and characteristics of topaz-hosted FI, i.e., relatively high T h (ca. 330-340°C), low salinity (ca. 7 wt.% eq. NaCl), and no sign of boiling. However, formation of quartz veins and evidence of fluid mixing with a meteoric fluid, contrast with the topazification alteration observed at the Echassières district, which was pervasive and unconnected to the surface. The features observed in FI from the Beauvoir greisen fluid correspond to more common wolframite vein type deposit. As an example, fluids in quartz veins from the Shirenzhang, Meiziwo and Yaoling W deposits displays similar properties (T h and salinity; [START_REF] Jiang | Fluid inclusion and isotopic (C, H, O, S and Pb) constraints on the origin of late Mesozoic vein-type W mineralization in northern Guangdong, South China[END_REF] as those in proximal veins in the Echassières district. They were interpreted as an orthomagmatic fluid which underwent boiling and subsequently precipitated wolframite ± cassiterite in quartz veins outside of the granitic sources.

U-Pb dating of cassiterite from greisen and W-Sn-bearing quartz veins in the Maopping deposit [START_REF] Chen | The Genetic Association between Quartz Vein-and Greisen-Type Mineralization at the Maoping W-Sn Deposit, Southern Jiangxi, China: Insights from Zircon and Cassiterite U-Pb Ages and Cassiterite Trace Element Composition[END_REF], provides proof for a coeval formation of greisen and distal veins and confirms that greisen alteration is a major depository for W-Sn mineralization. Globally, the "five floor" model (metal zoning in function of distance from the greisenized granite), developed for vein-type greisens in China (Gu, 1982; see also [START_REF] Mao | Geology and molybdenite Re-Os age of the Dahutang granite-related veinlets-disseminated tungsten ore field in the Jiangxin Province, China[END_REF][START_REF] Zhao | Genetic types, mineralization styles, and geodynamic settings of Mesozoic tungsten deposits in South China[END_REF][START_REF] Wang | Regional metallogeny of Tungsten-tin-polymetallic deposits in Nanling region, South China[END_REF] to explain distal wolframite-bearing quartz veins related to greisen alteration, is compatible with the processes that triggered precipitation of wolframite c during the Beauvoir greisen episode. For instance, similarly to formation of wolframite c, the role of extensional fracturing is emphasized for the multistage Xitian W-Sn and Pb-Zn ore deposit, where several scheelite generations involved cyclic reactivation of fault systems (Liu et al., 2019a) with repeated fluid boiling [START_REF] Liu | Double-vein (ore-bearing vs. ore-free) structures in the Xitian ore field, South China: Implications for fluid evolution and mineral exploration[END_REF].

Above, we highlighted that flashing was responsible for the precipitation of wolframite c, whereas boiling was inefficient. To our knowledge, this is the first time that flashing is clearly identified as the process generating W mineralization, while this mechanism is largely invoked in other metal deposit, such as Au-bearing quartz lodes [START_REF] Weatherley | Flash vaporization during earthquakes evidenced by gold deposits[END_REF][START_REF] Moncada | Mineralogical, petrographic and fluid inclusion evidence for the link between boiling and epithermal Ag-Au mineralization in the La Luz area, Guanajuato Mining District, México[END_REF] or porphyry Cu [START_REF] Yasami | Distribution of alteration, mineralization and fluid inclusion features in porphyry-high sulfidation epithermal systems: The Chodarchay example, NW Iran[END_REF]. However, several studies on greisen systems do recognize one boiling episode as the key factor to trigger W precipitation (e.g. [START_REF] Jiang | Fluid inclusion and isotopic (C, H, O, S and Pb) constraints on the origin of late Mesozoic vein-type W mineralization in northern Guangdong, South China[END_REF][START_REF] Li | Fluid inclusion characteristics as an indicator for tungsten mineralization in the Mesozoic Yaogangxian tungsten deposit, central Nanling district, South China[END_REF]. It is possible that at least in some of these occurrences a succession of boiling/flashing stages, as shown at Echassieres, took place. A drawn-out mineralization sequence involving cyclic boiling is a frequently recorded process in porphyry systems (Calagary, 2004;[START_REF] Ni | Evidence of fluid inclusions for two stages of fluid boiling in the formation of the giant Shapinggou porphyry Mo deposit, Dabie Orogen, Central China[END_REF][START_REF] Wang | Molybdenite Re-Os age, H-O-C-S-Pb isotopes, and fluid inclusion study of the Caosiyao porphyry Mo deposit in Inner Mongolia, China[END_REF].

Several studies, particularly in recent years, suggest that FI in gangue minerals may not provide the same data as those investigated in Sn-W ore minerals, particularly for quartz which shows systematically lower FI T h (e.g., [START_REF] Campbell | Comparison of fluid inclusions in coexisting (cogenetic?) wolframite, cassiterite, and quartz from St. Michael's Mount and Cligga Head, Cornwall, England[END_REF][START_REF] Moura | Metallogenesis at the Carris W-Mo-Sn deposit (Gerês, Portugal): constraints from fluid inclusions, mineral geochemistry, Re-Os and He-Ar isotopes[END_REF]Ni et al., 2015a;[START_REF] Legros | Multiple fluids involved in granite-related W-Sn deposits from the world-class Jiangxi province (China)[END_REF]. Nevertheless, in most of these studies, petrographic textures clearly show that the gangue minerals postdate the ore. This is not the case for wolframite b and c at Echassières, where extraordinary textural relationships between the second quartz generation and wolframite c in the Mazet veins provide undisputable evidence of synchronous crystallization of the two minerals (Fig. 6; see also Fig. 4 in [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF]. The timing of crystallization of wolframite b in the stockwork compared to that of topaz I is not as obvious. However, wolframite b crystals locally occur as inclusion in a single topaz crystal as well as in fractures that affected this mineral, implying that topaz and wolframite are contemporaneous. Also, quartz recrystallization during wolframite b precipitation (documented in [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF] trapped the same FI population as topaz I. Simultaneous crystallization of topaz and wolframite is also suggested for the Maoping deposit (China; [START_REF] Legros | Multiple fluids involved in granite-related W-Sn deposits from the world-class Jiangxi province (China)[END_REF], for which FI in wolframite and topaz display very similar Th.

In summary, this work confirms that, granted certain conditions such as very detailed petrographic observations and a large set of FI data, studying FI in gangue minerals can provide valuable information to reconstruct the behavior of the ore fluids. Different, likely complementary, constrains are obtained from studies where only FI in ore minerals are considered. Obviously, studying FI from both gangue and ore minerals permit the best comprehension of a system.

Conclusions

The following conclusions can be drawn from the fluid inclusion investigation on W mineralization in the Echassières area.

1. Although, at Echassières, three distinct episodes of W mineralization have been recognized (cf. [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF], we could not find primary fluid inclusions coeval with the first generation of wolframite (type a). The second generation, wolframite b, crystallized at ca. 400 to 550°C

while the great majority of wolframite c at ca. 250 to 260°C.

2. Cooling was the principal mechanism responsible for precipitation of wolframite b. Flashing of the fluid during fracturing, recorded by fluid inclusions at the Mazet veins notably, was the main cause for wolframite c crystallization. Therefore, this study confirms that both cooling and depressurization are factors that can trigger formation of wolframite ore.

3. At Echassières, the greisen fluids was not constrained to the granites, but circulated to some distance in the country rock inducing the formation of distal veins, a number of which carried W mineralization.

4. Greisen alteration at Beauvoir, contrary to most occurrences worldwide, cannot be tied directly to the exsolution of an orthomagmatic fluid but took place after boiling of such fluid, once crystallization was complete. Nevertheless, boiling/flashing episodes continued throughout the evolution of the greisen fluid.

5. Fluid inclusion data confirm the textural observations and trace chemical evidence [START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF] for the presence of two topaz generations in the La Bosse stockwork, topaz I and topaz II, originated from two distinct hydrothermal episodes, respectively, early (topazification) and later (Beauvoir) greisen alterations.

The critical observations obtained on the Beauvoir greisen highlighted above (greisen regional influence; role of boiling and flashing; succession of boiling/flashing stages) can provide important information on greisen formation processes and related mineralization, at the interior of a granite body as well as in regional veins, which can potentially improve future ore exploration.

this study. Two anonymous OGR reviewers provided thorough and constructive criticisms that helped improving the final version of this manuscript. Figure 10: A sketch depicting the regional veins examined in this study, their crosscutting relationships and the main textural relationships of the FI populations within their trapping context.

Figure captions

T h and salinity are also given.

  3.E), are regular in shape and vary in size from a few to ca. 50 µm. In these quartz veins, occur small sub-veinlets of recrystallized quartz that are connected with crystals of wolframite b (Fig 3.B), which we interpret to have formed during percolation of topazification fluid (see also,[START_REF] Monnier | Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)[END_REF]. Formation of these veinlets caused obliteration of the FI already present and trapping of a new FI population (Fig.3.D). The latter FI show regular shape with varied liquid/vapor ratios (ca 20 to 60 %; Fig.3.F).-Topaz veinsTopaz veins (corresponding to the first topaz generation, topaz I), commonly up to 8 cm wide and for the most part subvertical, crosscut the horizontal quartz veins of the La Bosse stockwork (Fig.4.A-B) below and above the Beauvoir granite. In addition to topaz, they contain various amounts of wolframite b and lepidolite to F-rich biotite micas series, plus minor rutile and cassiterite. Topaz crystals trap important quantities of FI, which distributed in clusters (primary FI) or along plans which affect only limited portions of a crystal (pseudosecondary FI). FI display tabular to irregular shapes (Fig.4.C), and the liquid phase occupies ca. 50 to 60 % of the inclusion volume, similarly to the FI described above from disseminated topaz in quartz veins. Some of the topaz veins are reactivated, and sealed by a second topaz generation (topaz II) and, in some cases, by an additional quartz generation (polyphased topaz veins; Fig.4.D). The second topaz generation contains regularly-shaped primary FI with high proportion of liquid (70 %; Fig.4.E). Lastly, primary FI occurring in quartz from the cores of these veins exhibit slightly higher proportion of liquid (ca. 70 to 80 %). The majority of all of the FI populations mentioned above from the polyphased topaz veins have regular shapes and measure from ca. 5 to 10 µm.-Aplitic dykesContemporaneous to the La Bosse stockwork, aplitic dykes consist mostly of K-feldspar relicts (now mostly clays + quartz) and, like the stockwork veins, are strongly affected by metamorphism and subsequent topazification. In these dykes, topaz I is closely associated with wolframite b (Fig.5.A-B)

  Fig. 5.C-G). Of these, only the greisen affects the Beauvoir granite (Fig. 5.D). FI in topaz I from the quartz vein share the same features than the other FI already described in this mineral, i.e., a regular, tabular to globular shape, and L filling ca. 50 to 60 % of the total volume (Fig. 5.F). FI interpreted to represent the greisen fluid are found in quartz from muscovite-quartz veinlets altering igneous minerals in the Beauvoir granite (Fig. 5.E), as well as in blue apatite replacing quartz in the stockwork vein (Fig. 5.G).

  7.B) forms a lode of several meters in width. Stibnite occurs in this vein, and textural evidence suggests it is either synchronous with quartz, or later. Its abundance is not related to the dimension of the veins, and locally one can observe veinlet composed entirely of stibnite (Fig.7.A). Quartz contains pseudosecondary trails of FI, accompanied by tiny acicular stibnite crystals (< 5 µm), as well as FI clusters close to larger stibnite crystals (Fig.7.C). These FI are irregularly shaped, approximately 5 µm in size, and contain a large proportion of the L phase (ca. 90 %).

  induced topazification, related to wolframite b and predating the granite intrusion; trapped FI in topaz I and in recrystallized quartz of the La Bosse stockwork veins; 2) Greisen alteration related to the Beauvoir granite, which induced muscovitization; trapped fluid inclusions in quartz from the pervasive alteration and subvertical greisen veins within the granite, in blue apatite in the stockwork enclave, in muscovite-quartz veinlets affecting the granite, in topaz II and quartz from the polyphase topaz veins, in proximal veins (Suchot et Mazet) and, possibly, Nades veins (Capitraux and Cros are not sufficiently constrained).

  9 and 11.A,H). Beauvoir greisen fluid is recorded in a wide variety of FI populations, which display a range of Th, covering a large interval from ca. 190 to 400°C (median values). Globally, FI trapped during greisen pervasive alteration of the Beauvoir granite (hydrothermal quartz and apatite, micro-fractures and -veinlets in igneous minerals) recorded elevated T h Fig. 11.G,L,P) with lower values for FI trapped in quartz veins, with no apparent correlation to the distance from the granite (190-260°C; Fig.11,C,D,E,K,N). Zoned crystals of the disseminated greisen type show markedly different T h for FI located in cores and in the rims. Data from the core show a peak at around 300°C while for the growth band they range from 400 to 450°C. However, FI in the outermost rim of these crystals have lower T h , with a peak at ca 250°C (Fig.11.P).Zoned quartz crystals of the Suchot veins display a similar trend although the values are lower, i.e., cores have a peak at 200°C while rims peak at about 230°C (Fig.11.D). A smaller difference can be observed between cores and rims of quartz from the Mazet veins (Fig.11.N).

  Figure12.C one can estimate that between crystallization of quartz[1] and quartz[START_REF] Bakker | Because of the very low salinities (approaching zero) obtained from FI in quartz 2 from the Mazet vein, we monitored[END_REF] generations,

  14.A), indicating dissolution/reprecipitation of the older generation, topaz I, during percolation of greisen fluids and precipitation of topaz II. The T h values for topaz I coincide with data reported in Harlaux et al. (2017; they did not recognize the topaz II generation, less abundant).

  15.B),given that the timing of wolframite precipitation (ca. 335 Ma;[START_REF] Harlaux | 40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U-Pb dating of wolframite[END_REF] corresponds to the Visean peak of peraluminous magmatism in the French Massif Central. This is consistent with the elevated homogenization temperatures of the fluid inclusions.Locally, in the La Bosse stockwork, small sub-veinlets of recrystallized quartz (Fig.3.D) trapped FI with two populations of FI. The highest liquid volume (70 to 80 %) displays lower T h (ca. 250 to 270°C) than those with liquid volume ca. equal to 60 % (370 to 395°C). The latter are in the same range as the primary FI found in topaz I, indicating that some quartz dissolution/reprecipitation occurred during wolframite b precipitation and topazification. The low-T h FI population has characteristics comparable to those observed in topaz II generation, so probably correspond to a later fluid percolation, most likely the Beauvoir greisen-forming fluid.Beauvoir greisen (wolframite c episode)In a study of fluid inclusions from late magmatic quartz and topaz at Beauvoir,[START_REF] Cuney | The Beauvoir topaz-lepidolite albite granite (Massif Central, France); the disseminated magmatic Sn-Li-Ta-Nb-Be mineralization[END_REF] documented the exsolution of an orthomagmatic fluid that underwent boiling, to form coexisting brine and a low-salinity fluid (Fig.15.C), and considered that the latter corresponds to the greisenizing fluid (L3 in their study) (Fig.12.C). The low salinities and moderate temperatures that we recorded in this study are consistent with this interpretation. The greisen episode related to the Beauvoir granite is a relatively long-lived alteration episode that started at temperatures of ca. 400°C and waned at about 190°C (Fig.12.C), but which did not involve an evolution in fluid chemistry, as shown by consistent quartz trace composition (c.f.,[START_REF] Monnier | Quartz traceelement composition by LA-ICP-MS as proxy for granite differentiation, hydrothermal episodes, and related mineralization: The Beauvoir Granite (Echassières district), France[END_REF]. A duration stretched over time agrees with a diachronic formation of the different quartz veins during the greisen episode. Greisen alteration initiated at relatively high temperature (400°C) with pervasive alteration which affected essentially the Beauvoir granite (recorded by the core of hydrothermal disseminated quartz) under lithostatic pressure (Fig. 15.D). Subsequently, an important fracturing event affecting the Beauvoir granite connected the greisen fluid to the surface. This produced flashing of the fluid (transition between Fig. 15.D and Fig. 14.E). Rapidly, pressure steadied roughly at hydrostatic values, as recorded by a marked peak of fluid inclusion data at ca. 250-280°C, indicating a period of intense greisen activity. This consisted of pervasive alteration of the granite (rim of disseminated quartz), and vein formation/reactivation in the host rock (e.g., Mazet veins, topaz II), due to local pressure variations (Fig. 15.E). At lower temperature (≤ 230°C), pervasive alteration seemed to be ineffective as indicated by the absence of FI with lower T h in the disseminated quartz oh the granite. Fluid flow was concentrated in veins, inside (greisen veins) and outside the granite body (Suchot vein, Nades vein; Fig. 15.F). Wolframite c is not a common mineral in the stockwork, formed during the flashing episode mentioned above, while mineralization was especially efficient in the Mazet area, likely triggered by a second flashing episode (Fig. 12.C). Antimony mineralization in the Nades area occurred only during the last peak of greisen activity at 200°C. During fluid cooling and development of greisen alteration,

Fig. 2 .

 2 B,D,G), and the FI T h recorded from the first to the last growth zones are practically the same. Such occurrence confirms the fact that numerous boiling episodes took place during the greisen fluid evolution, of which only a few could be evidenced in this study. Fluid boiling during greisen alteration plays a critical role in concentrating rare metals into the fluid phase, despite the antagonistic effect of possible dilution by mixing with meteoric fluid when

  ), show clearly different values of FI T h and different quartz textures, which probably points to a different origin for their respective Sb mineralizations. Based on quartz chemistry, Monnier et al. (2018) draw the attention to a possible genetic link between greisen fluid and Sb mineralization at Nades. This hypothesis is not contradicted by the FI data from this study (features of T h and FI petrography are similar for the Nades veins and Suchot-Beauvoir greisen veins), which suggest Nades may correspond to late stages of greisen activity (Fig 15.F). Nevertheless, salinity is slightly higher in Nades vein FI, which can probably be attributed to interaction of this fluid with the schist. Also, the consequent spread of T h recorded by FI from the Nades veins would indicate continuous Sb precipitation during fluid cooling, which contrasts with the Capitraux vein, where the FI and quartz texture record a single, sharp episode.

Figure 1 :

 1 Figure 1: Simplified geology and location of the study area. Sampling sites are indicated by stars. [A]:

Figure 2 :

 2 Figure 2: Petrography of FI observed in greisen alteration objects, i.e., in pervasive alteration of the

Figure 3 :

 3 Figure 3: A series of images depicting, at different scales, the genetic relationships of FI trapped

Figure 4 :

 4 Figure 4: Genetic relationships of FI observed in a topaz vein occurring in the La Bosse stockwork

Figure 5 :

 5 Figure 5: Genetic relationships of FI examined in altered La Bosse dyke (A-B), and in the stockwork

Figure 6 :

 6 Figure 6: Genetic relationships of FI from the Suchot (A-D) and Mazet (E-F) proximal quartz veins. [A]:

Figure 7 :

 7 Figure 7: Genetic relationships of FI from Sb-bearing quartz veins at Nades (A-C) and Capitraux (D-F).

Figure 8 :

 8 Figure 8: A sketch depicting the principal alteration objects examined in the Beauvoir granite, their

Figure 9 :

 9 Figure 9: A sketch depicting the principal alteration objects examined in the La Bosse stockwork area,

Figure 11 :

 11 Figure 11: Histograms displaying the homogenization temperature (Th) data for the different FI

Figure 12 .

 12 Figure 12. Diagram in pressure-temperature space, depicting isochores for the different FI

Figure 15 .

 15 Figure 15. A schematic model for the evolution of greisen alterations in the Beauvoir granite system.

Table captions Table 1 :

 captions1 Descriptive fluid inclusion data statistics for all populations studied in the Echassières district.

example of greisen fluid evolution, providing critical information on W behavior in orthomagmatic fluids, and on greisen-related rare-metal deposits.

Acknowledgments

We would like to acknowledge the BRGM (French Geological Survey), the CNRS (French National Center for Scientific Research) as well as the University of Toulouse for providing financial support to

within and outside the Beauvoir granite. In all panels, the presence of a chemical element denotes the timing of mineralization. [START_REF] Sibson | Stress/fault controls on the containment and release of overpressured fluids: Examples from gold-quartz vein systems in Juneau, Alaska; Victoria, Australia and Otago, New Zealand[END_REF] and [START_REF] Bons | A review of the formation of tectonic veins and their microstructures[END_REF]. [B]: Variation of fluid pressure during fracturing/sealing cycles. Ore deposition is triggered by instantaneous P f decrease. Modified after [START_REF] Sibson | High-angle reverse faults, fluid-pressure cycling, and mesothermal gold-quartz deposits[END_REF].