Augustin Dekoninck
email: augustin.dekoninck@unamur.be

Gilles Ruffet
email: gilles.ruffet@univ-rennes1.fr

Julien Baptiste
email: j.baptiste@brgm.fr

Robert Wyns
email: r.wyns@free.fr

Simon Philippo
email: simon.philippo@mnhn.lu

Yishen Zhang
email: yishen.zhang@kuleuven.be

Olivier Namur
email: olivier.namur@kuleuven.be

Petrogenesis and 40Ar/39Ar dating of hydrothermal romanechite from the sub-aerial fault-related

Keywords: romanechite, manganese, 40 Ar/ 39 Ar dating, epithermal mineralization, Mn oxide

come

Introduction

Assessing the age of mineral deposition is a key issue to understand the timescales of formation of mineral resources. When datable minerals are present, it is of great importance to identify the process by which they have precipitated in order to better constrain the ore genesis. Mn oxides have long been used to date supergene deposits due to the extensive occurrence of K-bearing Mn oxides (e.g., [START_REF] Ruffet | A geochronological and study of K-Mn oxides from the weathering sequence of Azul, Brazil[END_REF][START_REF] Li | Neogene weathering and supergene manganese enrichment in subtropical South China: An 40Ar/39Ar approach and paleoclimatic significance[END_REF][START_REF] Beauvais | Modes, tempo, and spatial variability of Cenozoic cratonic denudation: The West African example[END_REF][START_REF] Vasconcelos | 40Ar/39Ar and (U-Th)/He -4He/3He geochronology of landscape evolution and channel iron deposit genesis at Lynn Peak, Western Australia[END_REF][START_REF] Deng | 40Ar/39Ar dating of supergene Mn-oxides from the Zunyi Mn deposit, Guizhou Plateau, SW China: Implications for chemical weathering and paleoclimatic evolution since the late Miocene[END_REF][START_REF] Vasconcelos | Calibrating denudation chronology through 40 Ar/ 39 Ar weathering geochronology[END_REF][START_REF] Jean | Weathering history and landscape evolution of Western Ghats (India) from 40Ar/39Ar dating of supergene K-Mn oxides[END_REF][START_REF] Dekoninck | Genesis and 40Ar/39Ar dating of K-Mn oxides from the Stavelot Massif (Ardenne, Belgium): Insights into Oligocene to Pliocene weathering periods in Western Europe[END_REF][START_REF] Dekoninck | Multistage genesis of the late Cretaceous manganese karsthosted Tasdremt deposit (High Atlas, Morocco)[END_REF][START_REF] De Putter | Supergene manganese ore records 75 Myr-long Campanian to Pleistocene geodynamic evolution and weathering history of the Central African Great Lakes Region -Tectonics drives, climate assists[END_REF]. The most common species belong to the coronadite group [(Ba 2+ ,Pb 2+ ,Sr 2+ ,Na + ,K + ,)(Mn 4+ Mn 3+ or 2+ ) 8 O 16 ] [START_REF] Lippolt | 40 Ar/ 39 Ar ages of Precambrian manganese ore minerals from Sweden, India and Morocco[END_REF][START_REF] Ruffet | A geochronological and study of K-Mn oxides from the weathering sequence of Azul, Brazil[END_REF][START_REF] Vasconcelos | Mechanisms and kinetics of atmospheric, radiogenic, and nucleogenic argon release from cryptomelane during analysis[END_REF][START_REF] Vasconcelos | Direct dating of weathering phenomena by 40 Ar/ 39 Ar and K-Ar analysis of supergene K-Mn oxides[END_REF][START_REF] Vasconcelos | Age and duration of weathering by 40 K/ 40 Ar and 40 Ar/ 39 Ar analysis of potassium-manganese oxides[END_REF] forming a typical tunnel. The tunnel Mn oxides are built of chains of edge-sharing MnO 6 octahedra, and the chains share corners to produce frameworks that have tunnels with square or rectangular cross sections [START_REF] Post | Manganese oxide minerals: crystal structures and economic and environmental significance[END_REF]. The 2X2 tunnel crystallographic structure of coronadite allows a good retentivity of the 40 Ar* produced by the decay of radioactive structural 40 K, hence providing a remarkable tool for 40 [START_REF] Post | Manganese oxide minerals: crystal structures and economic and environmental significance[END_REF][START_REF] Turner | Refinement of the substructure and superstructure of romanechite[END_REF] is also suitable for 40 Ar/ 39 Ar geochronology [START_REF] Vasconcelos | K-Ar and 40 Ar/ 39 Ar geochronology of weathering processes[END_REF] as it can host structural K in the 2X3 tunnel structure [START_REF] Burns | Manganese oxides[END_REF][START_REF] Post | Manganese oxide minerals: crystal structures and economic and environmental significance[END_REF].

Although the majority of Mn oxides precipitate under supergene conditions, many deposits host Mn oxides directly formed from hydrothermal solutions [START_REF] Choubert | The Precambrian iron and manganese deposits of the Anti-Atlas, in: Genesis of Precambrian Iron and Manganese Deposits[END_REF][START_REF] Conly | Metalliferous Manganese Oxide Mineralization Associated with the Boléo Cu-Co-Zn District, Mexico[END_REF][START_REF] Decrée | Mn oxides as efficient traps for metal pollutants in a polyphase low-temperature Pliocene environment: A case study in the Tamra iron mine, Nefza mining district, Tunisia[END_REF][START_REF] Dekoninck | Mixed hydrothermal and meteoric fluids evidenced by unusual H-and O-isotope compositions of kaolinite-halloysite in the Fe(-Mn) Tamra deposit (Nefza district, NW Tunisia)[END_REF][START_REF] Glasby | The Vani manganese deposit, Milos island, Greece: A fossil stratabound Mn-Ba-Pb-Zn-As-Sb-W-rich hydrothermal deposit[END_REF][START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF][START_REF] Leal | The manganese deposits of the Pampean Ranges, Argentina[END_REF][START_REF] Liakopoulos | Nature and origin of the Vani manganese deposit, Milos, Greece: an overview[END_REF][START_REF] O'reilly | Petrographic and geochemical evidence for a hypogene origin of granite-hosted, vein-type Mn mineralization at the New Ross Mn deposits, Lunenburg County[END_REF][START_REF] Papavassiliou | New geochemical and mineralogical constraints on the genesis of the Vani hydrothermal manganese deposit at NW Milos island, Greece: Comparison with the Aspro Gialoudi deposit and implications for the formation of the Milos manganese mineralization[END_REF][START_REF] Roy | Manganese deposits[END_REF][START_REF] Roy | Mineralogy of the different genetic types of manganese deposits[END_REF]). The Mn oxide ore precipitates on top of the hydrothermal system by mixing of ascending hydrothermal fluids with descending oxygenated meteoric water [START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF][START_REF] Roy | Mineralogy of the different genetic types of manganese deposits[END_REF][START_REF] Roy | Manganese deposits[END_REF]. These sub-surface hypogene ores are composed of higher valence oxides such as romanechite, coronadite group minerals, pyrolusite and ramsdellite.

Whereas discriminating between Mn oxides formed under supergene versus epithermal conditions is relatively simple in active systems, it remains challenging in ancient ore systems (i.e. Gossans).

The Romanèche manganese deposit (Saône-et-Loire department, France)(Fig. 1) is predominantly composed of romanechite (type-locality mineral; [START_REF] Lacroix | Minéralogie de la France et de ses colonies: description physique et chimique des minéraux, étude des conditions géologiques et leurs gisements[END_REF]) located atop J o u r n a l P r e -p r o o f Journal Pre-proof a vein-type mineralization (Fig. 2; [START_REF] Bouladon | Etude sommaire du gisement de manganèse de Romanèche (Saône-et-Loire) (No. A1390-2[END_REF]. The Mn oxide ore is trapped in and aside the boundary fault-zone separating the Massif Central (MC) Variscan granitic basement and the Bresse graben filled by Mesozoic and Cenozoic sediments (Figs. 1 and2). The mineralization has long been considered as a supergene gossan capping an underlying and hidden hydrothermal mineralization [START_REF] Dolomieu | Description de la mine de manganèse de Romanèche[END_REF][START_REF] Drouot | Les gîtes de houille et les terrains des environs des forges et de la Chapelle-sous-Dun et sur les gîtes de manganèse et les terrains des environs de Romanèche[END_REF][START_REF] Hautmann | 40 Ar/ 39 Ar dating of central European K-Mn oxidesa chronological framework of supergene alteration processes during the Neogene[END_REF][START_REF] Lacroix | Minéralogie de la France et de ses colonies: description physique et chimique des minéraux, étude des conditions géologiques et leurs gisements[END_REF][START_REF] Lougnon | Ressources minières françaises : les gisements de manganèse[END_REF] due to the predominance of tetravalent Mn oxides.

However, [START_REF] Bouladon | Etude sommaire du gisement de manganèse de Romanèche (Saône-et-Loire) (No. A1390-2[END_REF] was the first to argue for an hydrothermal formation of the romanechite stage. Therefore, the Romanèche deposit can be useful to discuss the hydrothermal versus supergene formation of Mn oxides on top of vein-type mineralization. between the Massif Central and the Bresse Graben (modified after [START_REF] Chantraine | Carte géologique de la France à 1/1[END_REF]. [START_REF] Hautmann | 40 Ar/ 39 Ar dating of central European K-Mn oxidesa chronological framework of supergene alteration processes during the Neogene[END_REF] were the first, as part of a global Central European study of Mn-oxides, to conduct a geochronological analysis of this deposit in order to discuss weathering processes in Western Europe. Our study provides a more detailed analysis of the composition, ore genesis and timing of the Romanèche manganese deposit by combining Xray diffraction (XRD), scanning electron microscope with energy-dispersive spectroscopy (SEM-EDX), electron probe micro-analysis (EPMA), whole rock geochemistry and 40 Ar/ 39 Ar dating of romanechite. This dataset is used to refine the formation process of romanechite and J o u r n a l P r e -p r o o f to provide new ages in order to better understand the formation of the Romanèche deposits and other similar deposits worldwide.

Hydrothermal Mn oxide deposits

Hydrothermal Mn deposits are known worldwide. They all have low tonnage and reserves (e.g., Ouarzazate Mn field, Morocco; Cape Vani, Greece; SW, USA; [START_REF] Choubert | The Precambrian iron and manganese deposits of the Anti-Atlas, in: Genesis of Precambrian Iron and Manganese Deposits[END_REF][START_REF] Conly | Metalliferous Manganese Oxide Mineralization Associated with the Boléo Cu-Co-Zn District, Mexico[END_REF][START_REF] Decrée | Mn oxides as efficient traps for metal pollutants in a polyphase low-temperature Pliocene environment: A case study in the Tamra iron mine, Nefza mining district, Tunisia[END_REF][START_REF] Dekoninck | Mixed hydrothermal and meteoric fluids evidenced by unusual H-and O-isotope compositions of kaolinite-halloysite in the Fe(-Mn) Tamra deposit (Nefza district, NW Tunisia)[END_REF][START_REF] Glasby | The Vani manganese deposit, Milos island, Greece: A fossil stratabound Mn-Ba-Pb-Zn-As-Sb-W-rich hydrothermal deposit[END_REF][START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF][START_REF] Holtstam | Origin of a carbonate-hosted Fe-Mn-(Ba-As-Pb-Sb-W) deposit of Långban-type in central Sweden[END_REF][START_REF] Leal | The manganese deposits of the Pampean Ranges, Argentina[END_REF][START_REF] Liakopoulos | Nature and origin of the Vani manganese deposit, Milos, Greece: an overview[END_REF][START_REF] O'reilly | Petrographic and geochemical evidence for a hypogene origin of granite-hosted, vein-type Mn mineralization at the New Ross Mn deposits, Lunenburg County[END_REF][START_REF] Papavassiliou | New geochemical and mineralogical constraints on the genesis of the Vani hydrothermal manganese deposit at NW Milos island, Greece: Comparison with the Aspro Gialoudi deposit and implications for the formation of the Milos manganese mineralization[END_REF][START_REF] Roy | Manganese deposits[END_REF][START_REF] Roy | Mineralogy of the different genetic types of manganese deposits[END_REF]). These deposits are faultcontrolled and occur as veins that may be up to 1.5 m thick, extend horizontally up to 500 m and be traced to depths of up to 150 m. The vertical extension is rarely beyond 1 km [START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF]. The Mn oxide ore precipitates in the upper part of the hydrothermal system, showing an increasing gradation of higher valence oxides, including the Mn 4+ -Mn 3+ -bearing romanechite, coronadite group minerals, pyrolusite and ramsdellite [START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF][START_REF] Roy | Manganese deposits[END_REF][START_REF] Roy | Mineralogy of the different genetic types of manganese deposits[END_REF]. They show high concentrations of Ba, As, W, Sr, Be, Sb, Tl and Ge. They are consistently accompanied by barite, fluorite, quartz and carbonates as gangue minerals.

Silicification is the most common form of wall-rock alteration near the main Mn vein [START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF]. Sericitization is also reported. Barite and fluorite precipitation can either predate or postdate the Mn oxides. Arseniosiderite is found in some places and is a proof of hydrothermalism [START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF]. Below the high-valence Mn oxide ore, the deeper ore includes Mn 2+ -bearing minerals such as carbonates, silicate and oxides [START_REF] Fusswinkel | Evolution of unconformity-related MnFeAs vein mineralization, Sailauf (Germany): Insight from major and trace elements in oxide and carbonate minerals[END_REF][START_REF] Hewett | Stratified deposits of the oxides and carbonates of manganese[END_REF][START_REF] Madondo | Geochemical constraints on the genesis of the 'Montaña de Manganeso' vein-type Mn deposit, Mexican Plateau[END_REF].

Mineralization styles

The Romanèche manganese deposit is associated to the major fault-zone separating the Variscan granitic basement of the MC and the Triassic-Jurassic cover of the Bresse Graben.

The Mn ore follows this structure over an NNE striking length of c. 750 m (Figs. 1b and2). This fault has an offset of ~650 meters and has been active several times since the Variscan orogenesis [START_REF] Bouladon | Etude sommaire du gisement de manganèse de Romanèche (Saône-et-Loire) (No. A1390-2[END_REF]. The Romanèche deposit is no longer accessible; the numerous galleries have been closed by the regional authorities. The main access has been sealed by a concrete cap behind the Romanèche church and the other wells obstructed since the eighties.

Therefore, the today's Mn ore consists of mining wastes reused in some walls of the village or disseminated in the surrounding vineyards (see Appendix A). The only direct observations of the ore are minor Mn veins hosted in granites. Several Mn occurrences outcrop over a J o u r n a l P r e -p r o o f greater area with fluorite and barite [START_REF] Drouot | Les gîtes de houille et les terrains des environs des forges et de la Chapelle-sous-Dun et sur les gîtes de manganèse et les terrains des environs de Romanèche[END_REF], which defines a larger manganiferous field of 10x35 km² following the major fault direction (Fig. 1b). The Mn deposit consists of (i) two parallel lodes ("Grand filon" and "Petit filon") with a N35°E direction and dip angles of 50-75°SE hosted in Carboniferous granites ("Petit filon") or in the fault zone ("Grand filon") and (ii) a stratabound epigenetic mineralization replacing the Sinemurian limestone (Fig. 2; [START_REF] Lacroix | Minéralogie de la France et de ses colonies: description physique et chimique des minéraux, étude des conditions géologiques et leurs gisements[END_REF][START_REF] Bouladon | Etude sommaire du gisement de manganèse de Romanèche (Saône-et-Loire) (No. A1390-2[END_REF]. Both mineralization styles are reworked in the alluvium cover. The Romanèche ore combines romanechite with fluorite, quartz and barite.

Three major ore facies can be observed: (1) Mn crust (Fig. 3a), (2) Massive Mn ore (with or without fluorite; Fig. 3b), (3) Mn breccia (Fig. 3c). Hematite is also present in little amounts but becomes abundant at depth with barite [START_REF] Bouladon | Etude sommaire du gisement de manganèse de Romanèche (Saône-et-Loire) (No. A1390-2[END_REF][START_REF] Lacroix | Minéralogie de la France et de ses colonies: description physique et chimique des minéraux, étude des conditions géologiques et leurs gisements[END_REF] [START_REF] Bouladon | Etude sommaire du gisement de manganèse de Romanèche (Saône-et-Loire) (No. A1390-2[END_REF]. EPMA analyses has been carried on romanechite to obtain quantitative chemical analyses of major and minor elements. This mineralogical and petrographical determination was complemented by geochemical analyses of major and trace elements on 14 whole rock samples. Based on these results, we selected eight samples for 40 Ar/ 39 Ar geochronology.

Materials and methods

Forty

Mineralogical and petrographical analysis

Polished sections (16) were prepared for petrographic analyses at the Geomaterial Preparation Laboratory of the University of Namur (Belgium). XRD analyses of powdered samples were performed using an X-ray Panalytical X'Pert Pro diffractometer and a PHILLIPS PW3710 (CuKα radiation) of the PC2 platform (University of Namur), operating at 40 kV and 30 mA. The main mineral phases were identified using the ICDD View software with PDF-2 database (Powder Diffraction File 2019). Polished sections were studied by optical microscopy and electron microscopy using a JEOL 6010 LV and a JSM 7500-F SEM coupled with an ULTRA MINI-CUP Energy Dispersive Spectrometer (EDS) hosted at the Microscopy Service of the University of Namur. Four polished sections have also been observed and analyzed with a JEOL JXA-8530F EPMA equipped with a high brightness Schottky field emission electron gun (FEG), at the Department of Materials Engineering of KU Leuven (Leuven, Belgium). The following primary standards were used for K calibration: Mn metal (Mn), quartz (Si), almandine garnet (Al), barite (Ba), skutterudite (As, Co), hematite (Fe), plagioclase-An65 (Na), biotite (Mg), anhydrite (Ca), galena (Pb), celestite (Sr), sphalerite (Zn), tungsten metal (WO 3 ) and cuprite (Cu). Details about standards, accuracy, precision and analytical conditions are given in Appendix A -Supplementary Material. The water content is calculated using charge base structural formulae (Table 1). 92

Whole rock geochemistry

Whole rock geochemical analyses were performed at the Activation Laboratories Ltd (Canada) for major and trace elements (Table 2). Sample powders were prepared using a RETSCH PM 100 planetary ball mills (University of Namur). REE and trace elements were analysed by lithium metaborate/tetraborate fusion Mass Spectrometry (FUS-MS) and major elements by Fusion Inductively Coupled Plasma Optical Emission Spectrometry (FUS-ICP).

FeO was quantified by titration. Trace elements Ba, Sc, Be, Sr, Y, Zr and V were determined with FUS-ICP. FUS-ICP and ICP-OES was used to measure Pb and Mo concentrations, after a 4-acid digestion (hydrochloric-nitric-perchloric-hydrofluoric), when values were higher than the detection limits (10,000 ppm and 100 ppm, respectively). In addition, sulfate (SO 4 ) was determined by infrared (IR) spectrometry and fluor (F) by lithium borate fusion with ion selective electrode. Fe 2 O 3 t is the measured total amount of iron enclosing Fe 2 O 3 and FeO.

40 Ar/ 39 Ar K-Mn oxides geochronology

The eight romanechite sub-samples selected for geochronology were hand-picked from crushed rocks, washed in distilled water in an ultrasonic bath, and dried to avoid dust adsorbed on surface grains. Several grains have been taken for each sub-sample. The crystallinity, purity and composition were checked by XRD on aliquots (see Research data).

The reflexion line at ~3.10A on XRD pattern was used to identify the presence of coronadite group minerals and/or pyrolusite. In addition, each grain was investigated by SEM to control the degree of purity. Grains containing inclusions of minerals were discarded from the selection. Based on XRD and SEM analysis, we were able to select eight grains of pure romanechite and of sufficient size (3 to 7 mm) to ensure high bulk potassium (see SEM view of the selected grains in Appendix A). Four samples (19ROM05, 13, 20b and 23) have been duplicated to compare the results. A total of 12 grains have been analysed from the 8 subsamples. 40 Ar/ 39 Ar step-heating analyses were performed with a CO 2 laser probe coupled with a MAP 215 mass spectrometer, using the procedure described by [START_REF] Ruffet | Comparison of 40Ar-39Ar conventional and laser dating of biotites from the North Trégor Batholith[END_REF][START_REF] Ruffet | Rb/Sr and 40 Ar/ 39 Ar laser probe dating of high-pressure phengites from the Sesia zone (Western Alps): underscoring of excess argon and new age constraints on the high-pressure J o u r n a l P r e -p r o o f Journal Pre-proof metamorphism[END_REF][START_REF] Ruffet | A geochronological and study of K-Mn oxides from the weathering sequence of Azul, Brazil[END_REF][START_REF] Ruffet | Rb/Sr and 40 Ar/ 39 Ar laser probe dating of high-pressure phengites from the Sesia zone (Western Alps): underscoring of excess argon and new age constraints on the high-pressure J o u r n a l P r e -p r o o f Journal Pre-proof metamorphism[END_REF]. Irradiation of samples was performed at McMaster Nuclear Reactor (Canada) in the 8C facility and lasted 50 h with a global efficiency (J/h) of 8.15 x 10 -5 h -1 .

The irradiation standard was sanidine TCRs (28.608 ± 0.033 Ma; Renne et al., 1998Renne et al., , 2010Renne et al., and 2011)). Blank analyses were performed routinely before the first and after three to four runs, and were subtracted from the subsequent sample gas fractions. Apparent age errors were plotted at the 1σ level. These ages do not include errors on the 40 Ar * / 39 Ar K ratio and age of the monitor and decay constants. Plateau ages were calculated only if 70% or more of the 39 Ar K was released in at least three or more contiguous steps that yielded apparent ages within the 1σ of the integrated age of the plateau segment. Pseudo-plateau ages were defined with the same criteria if the plateau-segment contained less than 70% of the 39 Ar K released [START_REF] Cheilletz | 40 Ar/ 39 Ar dating of shear zones in the Variscan basement of Greater Kabylia (Algeria). Evidence of an Eo-Alpine event at 128 Ma (Hauterivian-Barremian boundary): Geodynamic consequences[END_REF]. The errors on the 40 Ar * / 39 Ar K ratio and age of the monitor and decay constants were included in the final calculation of the errors of the (pseudo-) plateau ages.

Analytical data and parameters used for calculations, such as isotopic ratios measured on pure K and Ca salts, mass discrimination, atmospheric argon ratios, J parameter, decay constants are in the electronic supplementary data material.

Results

J o u r n a l P r e -p r o o f

Petrography, mineral chemistry and paragenetic sequence

The Mn ore is composed of romanechite with colloform texture (Fig. 3a) constituted by aggregates of micrometric needles (usually 10-1000 µm length) (Fig. 3d), dendrites (Fig. 3e), or tabular crystals (Fig. 3f). Most of the romanechite grows onto the gangue minerals and host granite breccia (Figw. 3c and 3g). Small voids often remain empty (Fig. 3g). Colloform romanechite displays growth bands of slightly variable compositions (Figs. 3d andg) attributed to variations in the amounts of Ba, W and H 2 O. Two generations of romanechite are identified with crosscutting relations (Figs. 3h andi). The first generation (rmn-1) is Carich, when rmn-2 has no particular geochemical feature. Romanechite is a vein-filling mineral, meaning that no replacement texture has been observed or described, i.e. by replacement of Mn-rich carbonates or silicates. Romanechite is ubiquitous but some samples contain small amounts of cryptomelane, coronadite and hollandite. These minerals occur as veinlets or as filling of remaining voids in romanechite (Fig. 3h). Pyrolusite is observed as tiny aggregates of bipyramidal laths within the romanechite matrix (Fig. 3j). Hematite is early with respect to romanechite (Fig. 3k).

J o u r n a l P r e -p r o o f Gangue minerals are predominantly quartz and fluorite. Barite is also frequent, whereas arseniosiderite [Ca 2 Fe 3 (AsO 4 ) 3 O 2 .3(H 2 O)] and apatite are relatively scarce. Several generations of quartz are observed: one is younger than romanechite, whereas the other postdates the Mn oxides in fractures with the apatite veins (Fig. 3l). Purple fluorite, when associated with Mn oxides, but colourless or green in unmineralized samples, forms typical cubic crystals (Figs. 3j andm). Fluorite grows onto barite laths prior to ore-forming minerals and quartz (Fig. 3m). Some authors identified fluorite crystals coating the second generation of quartz [START_REF] Drouot | Les gîtes de houille et les terrains des environs des forges et de la Chapelle-sous-Dun et sur les gîtes de manganèse et les terrains des environs de Romanèche[END_REF], some of the fluorite coating romanechite [START_REF] Chermette | L'ancienne mine de manganèse de Romanèche (Saône-et-Loire)[END_REF]. In heavily mineralized samples, we suspect that some cubic voids (Fig. 3n) were initially fluorite ghosts. Arseniosiderite forms fibrous crystals growing onto hematite and is intersected by romanechite (Fig. 3o).

These petrographic observations show that barite, fluorite and quartz gangue minerals form early and successively in the paragenetic sequence (Figs. 3m and4). The Fe stage occurs at depth with hematite and arseniosiderite. Romanechite is the highly dominant Mn oxide.

Romanechite is late in the paragenetic sequence and likely coeval or younger to the fluorite stage: fluorite can either predate or postdate romanechite. In the latter case, this might be coeval with partial dissolution of the first fluorite generation. Pyrolusite and coronadite group minerals accompany the massive romanechite stage, forming the Mn ore. Apatite, barite and quartz have (re)crystallized later (Fig. 4).

J o u r n a l P r e -p r o o f The amount of H 2 O is deduced from the full tunnel site occupancy (=2) and averaged at 4.78 wt.% H 2 O. The studied samples deviate from the theoretical formula of romanechite by high amounts of W (0-2.4 wt.% W) and As (0-0.7 wt.%). The amount of K is between 0.01 and 0.26 wt.% K.

Finally, the average structural formulae of romanechite from 33 EPMA points is [Ba 0.54 Ca 0.04 Sr 0.02 Na 0.02 K 0.01 (Mn 4.57 W 0.03 Al 0.05 As 0.02 Fe 0.02 )O 10 .1.37H 2 O.

Whole rock geochemistry of the Mn(-F) ore

The host granite has a felsic composition with 69.9 to 74.2 wt.% SiO 2. This silica content is enhanced by silicification and weathering. The MnO concentration is low, ranging between 0.02 and 0.04 wt.%. The other major elements have variable concentrations. Arsenic (17-48 ppm As) and tungsten (15-20 ppm W) are relatively high in comparison with the Upper Continental Crust (Fig. 5a). Rare Earth Elements profiles normalized on the Upper Continental Crust are flat (Fig. 5b).

J o u r n a l P r e -p r o o f

Journal Pre-proof

The major element contents of the Mn ore are MnO (0.03-58.9 wt.%), F (0-42.2 wt.%), CaO (0.2-63.6), SiO 2 (0.4-89.1 wt.%), Fe 2 O 3 (0.3-16.0 wt.%) and Ba (1.1-24.8 wt.%). The low MnO value is due to high content of the gangue minerals. Some elements, usually considered as trace elements show high concentrations; W (5-13,200 ppm), As (16-6,760 ppm) and Sr (364-3,337 ppm Sr). Tungsten is hosted by romanechite (Table 1). The other metals are slightly enriched (Co, Cu, Zn; Table 2; Fig. 5a). Rare Earth Elements are not enriched (19.7-95.0 ppm REE) compared to the UCC, characterized by flat patterns with a slight negative Ce anomaly (Table 1; Fig. 5b). Earth Element patterns of the Mn ore, Fe-Mn ore and host rocks. Ca: calcite; Rmn: romanechite; Qz:quartz; Flr: fluorite; Brt: barite. 40 Ar/ 39 Ar analyses of romanechite provide ages spanning the period between late Chattian to Fig. 6; Table 3). 40 Ar/ 39 Ar age spectra (Fig. 6; Table 3) yields five plateau ages at 18.2 ± 0.5 Ma [19ROM30; 85.9% of total 39 Ar K released and mean square of weighted deviates (MSWD)=0.26], 23.0 ± 0.4 Ma (19ROM05; 92.1% of total 39 Ar K released and MSWD=0.74), 23.4 ± 0.5 Ma (19ROM20b; 86.2% of total 39 Ar K released and MSWD=0.05), 23.5 ± 0.4 Ma (19ROM29; 84.3% of total 39 Ar K released and MSWD=0.54) and 25.2 ± 0.3 Ma (19ROM21a; 94.3% of total 39 Ar K released and MSWD=0.44) and a concordant pseudo-plateau age at 22.8 ± 0.3 Ma (61.2% of total 39 Ar K released and MSWD=0.20) provided by duplicate experiment performed on sample 19ROM05. These plateau ages are validated by the processing in the inverse isochron diagrams (correlation diagram) ( 36 Ar/ 40 Ar vs. 39 Ar K / 40 Ar*; [START_REF] Hanes | An 40 Ar/ 39 Ar geochronological and electron microprobe investigation of an Archaean pyroxenite and its bearing on ancient atmospheric compositions[END_REF][START_REF] Roddick | The evolution of excess argon in alpine biotitesa 40Ar-39Ar analysis[END_REF][START_REF] Turner | Argon 40-argon 39 dating: the optimization of irradiation parameters[END_REF] with initial ratios ( 40 Ar/ 36 Ar) i indistinguishable from the atmospheric ratio ( 40 Ar/ 36 Ar = 298.56 according to [START_REF] Lee | A redetermination of the isotopic abundances of atmospheric Ar[END_REF]) and MSWDs in accordance with the statistical validity criteria. All these experiments provide rather flat 37 Ar Ca / 39 Ar K (# Ca/K) spectra with ratios in the range 0.6-1.2. Note that the 37 Ar Ca / 39 Ar K (# Ca/K) ratios calculated for romanechite are significantly higher than those usually observed for Mn oxides of the coronadite group (~0.1). These ages are consistent with those of [START_REF] Hautmann | 40 Ar/ 39 Ar dating of central European K-Mn oxidesa chronological framework of supergene alteration processes during the Neogene[END_REF] at 25.8±0.4, 24.9±0.4, 20.9±0.7 and 20.8±0.6 Ma. The low-temperature steps (0-10% of 39 Ar K ) of these age spectra are characterised by notably high rates and amounts of atmospheric argon, as shown by the clusters of points along the 36 Ar/ 40 Ar axis of the inverse isochron diagrams, as well as by anomalously high apparent ages that decrease rapidly (Fig. 6). These low temperature disturbances could express the J o u r n a l P r e -p r o o f degassing of poorly crystallized phases or very small crystallites affected by 39 Ar K recoil during the irradiation process [START_REF] Ruffet | A geochronological and study of K-Mn oxides from the weathering sequence of Azul, Brazil[END_REF][START_REF] Vasconcelos | K-Ar and 40 Ar/ 39 Ar geochronology of weathering processes[END_REF].

40 Ar/ 39 Ar geochronology

Analyses of samples 19ROM13, produce disturbed age spectra with low to high temperature steps that trace a hump followed by a saddle (Fig. 7). Maximum apparent ages from duplicate analyses of romanechite from sample 19ROM13, which cannot exceed the age of Jurassic carbonates, are consistent with the age of the host granite, at c. 320 Ma, and suggest contamination by Variscan material, probably K-feldspars, which was not detected during the Mn oxide selection process. The shape of their 37 Ar Ca / 39 Ar K (# Ca/K) spectra is antithetical, with the lowest ratios (about 0.1) yielded by steps with the oldest apparent ages and conversely for the highest ratios (about 1)

which are provided by the constitutive steps of the saddle basements (Fig. 7). These observations suggest that the first stage of the degassing of these samples is dominated by the contaminating phase, old and Ca-poor, such as K-feldspars, while the second stage is dominated by degassing of the romanechite, younger and Ca-rich. This interpretation most likely applies to all the disturbed age spectra identified in this study, which have similar shapes but with varying amplitudes depending on the relative proportions of contaminating and romanechite phases, as shown in Figure 8. The decrease of the apparent age and the progressive attenuation of their sigmoidal shape are correlated with the progressive increase and flattening of the corresponding 37 Ar Ca / 39 Ar K spectra. This trend leads to perfectly flat age and 37 Ar Ca / 39 Ar K spectra that show the degassing of pure romanechite (e.g., 19ROM21a; Fig. 8), free of any Variscan contamination. The slightly higher values of the 37 Ar Ca / 39 Ar K ratios of romanechite 19ROM15 and 19ROM23 suggest that fluorite (CaF 2 ) may have interfered with the outgassing of 37 Ar Ca , artificially increasing the measured Ca/K ratios (Fig. 8).

The new results (Figs. 6 and9) and those which were obtained by [START_REF] Hautmann | 40 Ar/ 39 Ar dating of central European K-Mn oxidesa chronological framework of supergene alteration processes during the Neogene[END_REF] at 25.8±0.4, 24.9±0.4, 20.9±0.7 and 20.8±0.6 Ma cover a period of 7.6 Ma, between 25.8±0.4 Ma and 18.2±0.5 Ma (Fig. 9). It is not possible, at this stage, to determine whether the mineralization process was continuous or discontinuous and whether its duration was fully recorded.

J o u r n a l P r e -p r o o f

Discussion

Ore deposit model

Romanechite has been described in various environments, from weathering crusts to hydrothermal deposits [START_REF] Dill | The "chessboard" classification scheme of mineral deposits: Mineralogy and geology from aluminum to zirconium[END_REF][START_REF] Nicholson | Contrasting mineralogical-geochemical signatures of manganese oxides; guides to metallogenesis[END_REF][START_REF] Perseil | Contribution à la connaissance des romanéchites et des cryptomélanescoronaditeshollandites. Traits essentiels et paragenèses[END_REF]. First considered as a supergene gossan capping an underlying and hidden hydrothermal mineralization [START_REF] Dolomieu | Description de la mine de manganèse de Romanèche[END_REF][START_REF] Drouot | Les gîtes de houille et les terrains des environs des forges et de la Chapelle-sous-Dun et sur les gîtes de manganèse et les terrains des environs de Romanèche[END_REF][START_REF] Hautmann | 40 Ar/ 39 Ar dating of central European K-Mn oxidesa chronological framework of supergene alteration processes during the Neogene[END_REF][START_REF] Lacroix | Minéralogie de la France et de ses colonies: description physique et chimique des minéraux, étude des conditions géologiques et leurs gisements[END_REF][START_REF] Lougnon | Ressources minières françaises : les gisements de manganèse[END_REF], the new geochemical and petrographical data from this study support a fault-controlled hydrothermal formation of the romanechite ore.

The fluorite-barite gangue is common in hydrothermal Mn deposits [START_REF] Hewett | Stratified deposits of the oxides and carbonates of manganese[END_REF][START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF][START_REF] Holtstam | Origin of a carbonate-hosted Fe-Mn-(Ba-As-Pb-Sb-W) deposit of Långban-type in central Sweden[END_REF][START_REF] Leal | The manganese deposits of the Pampean Ranges, Argentina[END_REF][START_REF] Roy | Manganese deposits[END_REF][START_REF] Roy | Mineralogy of the different genetic types of manganese deposits[END_REF] whereas it is unusual in other genetic types such as sedimentary, metamorphic or supergene deposits [START_REF] Dill | The "chessboard" classification scheme of mineral deposits: Mineralogy and geology from aluminum to zirconium[END_REF][START_REF] Kuleshov | Isotope geochemistry: the origin and formation of manganese rocks and ores[END_REF][START_REF] Maynard | Manganiferous sediments, rocks, and ores[END_REF][START_REF] Varentsov | Manganese ores of supergene zone: Geochemistry of formation[END_REF]. In addition, silicification is the form of J o u r n a l P r e -p r o o f wall-rock alteration associated with the Mn oxide ore [START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF]. Quartz precipitates either before or after the Mn oxide within the ore zone (Figs. 3i,3j and 4).

The Mn ore is trapped in and coplanar with the major fault zone (Figs. 1b and2). Relation with tectonics is expressed in the ore by a breccia composed of granite fragments cemented by romanechite and gangue minerals (Fig. 3c). The Mn ore is itself brecciated and cemented by successive generations of romanechite (Figs. 3h andi). In addition, the clayey zone at the wall of the Mn vein contains fragments of the Jurassic limestones [START_REF] Lougnon | Ressources minières françaises : les gisements de manganèse[END_REF] and the romanechite ore (Fig. 2, [START_REF] Bouladon | Etude sommaire du gisement de manganèse de Romanèche (Saône-et-Loire) (No. A1390-2[END_REF]. Accordingly, this fault was active several times before and after the Mn ore deposition.

Dissolution of fluorite inside romanechite (Fig. 3n) and its (re)deposition as a coating on romanechite (Fig. 4, [START_REF] Chermette | L'ancienne mine de manganèse de Romanèche (Saône-et-Loire)[END_REF] supports that romanechite was formed in the same temperature range than fluorite. These temperatures are most likely between 100-200°C, according to data from other epithermal Mn deposits having similar mineralogical composition [START_REF] Glasby | The Vani manganese deposit, Milos island, Greece: A fossil stratabound Mn-Ba-Pb-Zn-As-Sb-W-rich hydrothermal deposit[END_REF][START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF][START_REF] Hewett | Deposits of the manganese oxides; supplement[END_REF][START_REF] Hewett | Deposits of the manganese oxides[END_REF][START_REF] Leal | The manganese deposits of the Pampean Ranges, Argentina[END_REF][START_REF] Liakopoulos | Nature and origin of the Vani manganese deposit, Milos, Greece: an overview[END_REF][START_REF] Madondo | Geochemical constraints on the genesis of the 'Montaña de Manganeso' vein-type Mn deposit, Mexican Plateau[END_REF][START_REF] Papavassiliou | New geochemical and mineralogical constraints on the genesis of the Vani hydrothermal manganese deposit at NW Milos island, Greece: Comparison with the Aspro Gialoudi deposit and implications for the formation of the Milos manganese mineralization[END_REF][START_REF] Voudouris | Arsenian Pyrite and Cinnabar from Active Submarine Nearshore Vents, Paleochori Bay, Milos Island, Greece[END_REF]. The dissolved fluorite crystals observed in some parts of the Romanèche deposit (Fig. 3n) suggests that acidic fluids post-dated romanechite precipitation [START_REF] Richardson | The solubility of fluorite in hydrothermal solutions, an experimental study[END_REF][START_REF] Zhang | Experimental Study of Dissolution Rates of Fluorite in HCl-H2O Solutions[END_REF]. Low pH did not remobilize the Mn hosted in romanechite because the high Eh was maintained under prevailing sub-surface conditions.

Mineral zoning is clearly established in space and time with the occurrence of Fe oxides at depth and tetravalent Mn oxides in the upper levels of the mineralization (Fig. 2, [START_REF] Bouladon | Etude sommaire du gisement de manganèse de Romanèche (Saône-et-Loire) (No. A1390-2[END_REF]. This trend is also materialized by the successive crystallization of hematite, arseniosiderite, romanechite and coronadite group minerals (Fig. 4). The vertical mineral zoning appears to be controlled by the O 2 conditions and cooling of the ascending hydrothermal solution [START_REF] Hewett | Stratified deposits of the oxides and carbonates of manganese[END_REF][START_REF] Perseil | Contribution à la connaissance des romanéchites et des cryptomélanescoronaditeshollandites. Traits essentiels et paragenèses[END_REF]. This O 2 and temperature dependency is responsible for the separation of Fe from Mn in the vertical sequence.

Seemingly, the Romanèche ore corresponds to the uppermost part of the hydrothermal system as no reduced Mn 2+/3+ -bearing minerals (sulphides, carbonates or silicates) have been reported.

As such, romanechite precipitated in an open system (Figs. 3a, b, c and f), directly from the mineralizing fluid and not by replacement of lower valence Mn-bearing minerals as observed J o u r n a l P r e -p r o o f in other subsurface Mn oxide ores [START_REF] Dekoninck | Multistage genesis of the late Cretaceous manganese karsthosted Tasdremt deposit (High Atlas, Morocco)[END_REF][START_REF] Dekoninck | Genesis and 40Ar/39Ar dating of K-Mn oxides from the Stavelot Massif (Ardenne, Belgium): Insights into Oligocene to Pliocene weathering periods in Western Europe[END_REF][START_REF] Dekoninck | Detailed mineralogy and petrology of manganese oxyhydroxide deposits of the Imini district (Morocco)[END_REF][START_REF] Lafforgue | Geological and geochemical constrains on the genesis of the sedimentary-hosted Bou Arfa Mn(-Fe) deposit (Eastern High Atlas, Morocco)[END_REF]. In this context, it is unlikely that the romanechite-bearing ore derived from in situ supergene weathering such as in gossan.

Geochemical analyses of samples from the Romanèche deposit show an enrichment in Mn-Ba-As-W (Table 1; Fig. 5a), which is consistent with the Mn-As-Ba-Sr enrichment observed in epithermal Mn deposits [START_REF] Glasby | The Vani manganese deposit, Milos island, Greece: A fossil stratabound Mn-Ba-Pb-Zn-As-Sb-W-rich hydrothermal deposit[END_REF][START_REF] Hewett | Deposits of the manganese oxides; supplement[END_REF]. The ternary plot of [START_REF] Bonatti | Classification and Genesis of Submarine Iron-Manganese Deposits[END_REF] and the Nicholson's discrimination diagram [START_REF] Nicholson | Contrasting mineralogical-geochemical signatures of manganese oxides; guides to metallogenesis[END_REF] support the hydrothermal origin of the Mn ore, and in particular the strong enrichment in As and other trace metals (Fig. 10, Tables 1 and2). Nevertheless, these plots cannot be used as a proof of origin because Mn oxides from the supergene zone of polymetallic deposits may also carry a high metal content without being of hydrothermal origin [START_REF] Vasconcelos | Geochronology of Weathering in the Mt Isa and Charters Towers Regions, Northern Queensland[END_REF].

However, the Romanèche Mn deposit does not contain ore-forming minerals hosting high amounts of metals, such as sulphides as the primary source of metals. Instead, the Mn ore is predominantly composed of romanechite and hematite at depth (Fig. 2). Therefore, the geochemistry of the romanechite ore would represent the composition of the fluid from which it has precipitated. In addition, the substantial enrichment in W, up to 1.4 wt.% (Table 1), is consistent with data from hydrothermal-epithermal Mn oxide deposits having similar mineralogy and geochemistry [START_REF] Glasby | The Vani manganese deposit, Milos island, Greece: A fossil stratabound Mn-Ba-Pb-Zn-As-Sb-W-rich hydrothermal deposit[END_REF][START_REF] Holtstam | Origin of a carbonate-hosted Fe-Mn-(Ba-As-Pb-Sb-W) deposit of Långban-type in central Sweden[END_REF]. Tungsten enrichment is usually connected to volcanogenic-magmatic process (i.e. skarns, pegmatite, porphyries, VMS) and has a particular affinity with manganese to form the wolframite series [START_REF] Dill | The "chessboard" classification scheme of mineral deposits: Mineralogy and geology from aluminum to zirconium[END_REF]. Tungsten-rich romanechite vein-type mineralization hosted in granite may indicate a direct contribution of magmatic fluids in the geochemistry of the ore. Either the low content of W of the mineralizing fluid, the low temperature and the high O 2 fugacity may prevent the precipitation of W-rich minerals, such as wolframite. However, the source of the Mn-Ba-As-W remains elusive, but O 2 -poor acidic fluids would transport the metals regardless of their origin. [START_REF] Hautmann | 40 Ar/ 39 Ar dating of central European K-Mn oxidesa chronological framework of supergene alteration processes during the Neogene[END_REF] previously dated four romanechite samples at 25.8±0.4, 24.9±0.4, 20.9±0.7 and 20.8±0.6 Ma which they interpret as a record of a long weathering event (Table 3). However, this interpretation fails to explain some of the key observations described above (Fig. 10): romanechite formed by ascending circulation of hot mineralizing fluids. The new 40 Ar/ 39 Ar ages between 25.2±0.3 to 18.2±0.5 Ma (Fig. 6) combined with J o u r n a l P r e -p r o o f volcanic activity occurred elsewhere. The magmatic process involved partial melting in an E-W extensional regime that reactivated N-S Variscan fault zones [START_REF] Michon | The evolution of the Massif Central Rift; spatio-temporal distribution of the volcanism[END_REF].

Interpretation of romanechite radiometric ages

The period covered by volcanic activity and reactivation of faults is perfectly coherent with the ~26-18 Ma period recovered from romanechite dating (Table 3).

The high heat flow beneath the MC [START_REF] Lucazeau | Interpretation of heat flow data in the french massif central[END_REF], materialized by intraplate magmatic activity probably enhanced circulation of hot mineralizing fluids. We support a primary hydrothermal activity related to the widespread volcanic activity to account for the unusual enrichment in some granitophile elements, such as tungsten (Fig. 5). As indeed high heat flow and widespread volcanism would contribute to hydrothermal activity in the area, we cannot rule out a SedEX-like formation process. The cumulated thickness of ~3,000 meters of Cenozoic sediments in the Bresse Graben [START_REF] Sissingh | Comparative Tertiary stratigraphy of the Rhine Graben, Bresse Graben and Molasse Basin: correlation of Alpine foreland events[END_REF] would account for the generation of basinal fluids by compaction and their upward migration along the margins of the graben. The Mn-Ba-As-W enrichment observed in the romanechite ore (Fig. 5) may have been leached by hydrothermal fluids from the granitic basement rocks. In any case, the bordering fault zone channelled the mineralizing fluid precipitating an epithermal ore type.

When these fluids cool and reach more oxygenated wet horizons (i.e., watertable), they precipitated the H 2 O-rich Mn oxides [START_REF] Glasby | The Vani manganese deposit, Milos island, Greece: A fossil stratabound Mn-Ba-Pb-Zn-As-Sb-W-rich hydrothermal deposit[END_REF][START_REF] Hewett | Veins of hypogene manganese oxide minerals in the southwestern United States[END_REF]. The Romanèche area is considered to be subaerial during the deposition of the Mn mineralization [START_REF] Sissingh | Comparative Tertiary stratigraphy of the Rhine Graben, Bresse Graben and Molasse Basin: correlation of Alpine foreland events[END_REF] and likely looked like a hot spring apron system. The Sinemurian carbonates host the epigenetic stratabound mineralization by fluid-rock interaction (Fig. 2).

Overall, it means that other fault-controlled mineralization may also be related to the hydrothermal events reported in this study. This would be true at least for the northern MC domain and possibly in connection with reactivated faults occurring along the West-European graben segments, where Oligocene-Miocene volcanic activity has been reported (i.e., Vosges, Black Forest; [START_REF] Wilson | Tertiary-Quaternary intra-plate magmatism in Europe and its relationship to mantle dynamics[END_REF].

Conclusions

This study provides geochemical, petrographical and geological evidences for hydrothermal origin of the Romanèche manganese deposit. Careful 40 Ar/ 39 Ar dating of pure romanechite grains provides reliable plateau-ages between 26 Ma and 18 Ma, corresponding to various pulses of hydrothermal activity. This study confirms the great applicability of this mineral for geochronological studies, despite its relatively low K content (0.1-0.6 wt.% K). The good crystallinity of romanechite due to its hydrothermal formation likely favours a better J o u r n a l P r e -p r o o f

Journal Pre-proof production and/or retention of the radiogenic argon than poorly crystallized phases of supergene origin. The age of the hydrothermal system of Romanèche is coeval with grabenrelated fault reactivation and distant volcanic activity in the northern Massif Central, which provides time constrain for fault-related mineralization events along the Massif Central, and possibly along the West-European graben segments.

Fig. 1 .

 1 Fig. 1. Geological situation of the Romanèche Mn deposit and surrounding Mn mineralization. a. Location of the Romanèche deposit among other Mn occurrences of the French Massif Central. b. Geological map of the Romanèche Mn(-F) manganese field

  and locally arseniosiderite Ca 2 Fe 3 O 2 (AsO 4 ) 3 .3H 2 O (type-locality mineral; Dufrénoy, 1842).

Fig. 2 .

 2 Fig. 2. N125°E cross-section through the Romanèche deposit[START_REF] Bouladon | Etude sommaire du gisement de manganèse de Romanèche (Saône-et-Loire) (No. A1390-2[END_REF].

  -four samples have been collected in the field. Most of them come from mining wastes in vineyards and village walls around the main historical mining wells (see Appendix A for details and photographs). One sample is from the collection of the Museum National d'Histoires Naturelles du Luxembourg. The initial location of these samples is unknown but J o u r n a l P r e -p r o o f Journal Pre-proof they likely come from the most important past extraction sites. The mineralogy of 32 samples of these samples was determined by X-ray diffraction. Sixteen samples were further selected and examined in detail by optical and scanning electron microscopy on polished sections.

  . 0. 1 7 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 4. J o u r n a l P r e -p r o o f

Fig. 3 .

 3 Fig. 3. Petrographic observation of the romanechite-rich ore of Romanèche. a. Hand specimen of Mn crust in the host granite at the Les Espagnes deposit. b. Hand specimen of the massive Mn ore from the Romanèche deposit. c. Hand specimen of the Mn ore breccia containing fragments of the host granite. d. Back-scattered electron (BSE) view of colloform romanechite around a quartz-fluorite nuclei. e. SEM-BSE view of typical dendrites of romanechite. f. SEM-BSE view of prismatic tabular crystals of romanechite (dated sample).

Fig. 4 .

 4 Fig. 4. Paragenetic sequence of the Romanèche Mn deposit based on petrographic observations and SEM analyses.

Fig. 5 .

 5 Fig. 5. Geochemistry of the Mn ore, Fe-Mn ore and host rocks compared to the Upper Continental Crust (UCC; McLennan, 2001). a. Trace element patterns of the romanechitebearing Mn ore, Fe-Mn ore and granitic basement rocks in the Romanèche deposit. b. Rare

(Fig. 6 .Fig. 8 .

 68 Fig.6.40 Ar/ 39 Ar age and 37 Ar Ca / 39 Ar K (# Ca/K with 37 Ar Ca / 39 Ar K = CaO/K 2 O / 2.179;[START_REF] Deckart | Age of Jurassic continental tholeiites of French Guyana, Surinam and Guinea: Implications for the initial opening of the Central Atlantic Ocean[END_REF] spectra and inverse isochron ( 36 Ar/ 40 Ar vs. 39 Ar/ 40 Ar) diagrams of romanechite samples 19ROM05, 20b, 21a, 23, 29 and 30 from Romanèche deposit. Detailed results are present in supplementary data. Apparent age error bars are at the 1σ level; errors in the J-parameter are not included. Plateau, pseudo-plateau and isochron ages are given with 1σ uncertainties and include errors in the J-parameter. Grey ellipses are excluded from isochron regression, MSWD stands for Mean Squares of Weighted Deviates.

Fig. 9 .

 9 Fig. 9. Frequency (probability density) diagrams of apparent ages of resized age spectra (steps of 5% of 39 Ar K released ; see De Putter and Ruffet (2020) and Tremblay et al. (2020) for explanation). Validated ages (plateau and pseudo-plateau ages) are plotted as yellow stars (error bars are smaller than the size of the symbols).

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

 12345678910 Figure 1

  Ar/ 39 Ar dating. Far less known,

	romanechite [Ba 0.66 Mn 4+ 3.68 Mn 3+ 1.32 O

10 .1.34.H 2 O] or (Ba,H 2 O) 2 (Mn 3+ ,Mn 4+ ) 5 O 10

Table 1 .

 1 EPMA analysis of romanechite in the Romanèche Mn deposit.

Table 2 .

 2 Major

oxides (in wt. %) and trace element (in ppm) geochemical analyses. LOI: Lost on ignition. Mineral abbreviation: ca=calcite, ro=romanechite, q=quartz, he=hematite, ba=barite, f=fluorite, ho=hollandite.

Table 2

 2 Summary of significant geochronological information and validated plateau ages (PA) and Isochron ages based on 40 Ar/ 39 Ar and 37 Ar Ca / 39 Ar K spectra and Inverse isochron

Acknowledgment

This work was funded and carried out in the framework of the BRGM-TOTAL project Source-to-Sink. We appreciate the help of Prof. J. Wouters and Dr. N. Tumanov of the PC2 platform (UNamur) for collecting XRD patterns. This research also used the resources of the Electron Microscopy Service located at the University of Namur ("Plateforme Technologique Morphologie -Imagerie"). We are delighted to Ir. Pieter L'Hoest of the Department of Materials Engineering at the Katholiek Universiteit Leuven (KUL) for some of the EPMA analyses. We are also delighted to two anonymous reviewers who have greatly improved this manuscript.

those obtained by [START_REF] Hautmann | 40 Ar/ 39 Ar dating of central European K-Mn oxidesa chronological framework of supergene alteration processes during the Neogene[END_REF] highlight mineralizing events from late Chattian to early Burdigalian (Table 3). It is unlikely that the hydrothermal ore system was active continuously during c. 7.6 My. We rather hypothesize several pulses at ~25 Ma, ~23 Ma, ~21 Ma and ~18 Ma. Therefore, the romanechite ages attest to a regular hydrothermal activity over at least c. 7.6 My along the fault zone delimiting the contact between the MC and the Bresse graben. Therefore, it is also likely that our age data is a testimony of the (re)activation age of the fault system. This study further confirms the reliability of the 40 Ar/ 39 Ar dating of romanechite in hydrothermal Mn ore. Fig. 10. a. Diagnostic plot of hydrothermal geochemical signature for Mn deposits [START_REF] Nicholson | Contrasting mineralogical-geochemical signatures of manganese oxides; guides to metallogenesis[END_REF] applied to the Romanèche Mn deposit. b. Mn-Fe-(Ni+Cu+Co) ternary differentiation diagram (mass basis) for marine hydrogenetic and hydrothermal Mn oxides [START_REF] Bonatti | Classification and Genesis of Submarine Iron-Manganese Deposits[END_REF].

The western part of the European plate was affected by extensive rifting episodes during the Tertiary [START_REF] Bois | Initiation and evolution of the Oligo-Miocene rift basins of southwestern Europe: Contribution of deep seismic reflection profiling[END_REF][START_REF] Prodehl | The European Cenozoic rift system[END_REF][START_REF] Ziegler | European Cenozoic rift system[END_REF]. E-W extensional stress fields led to the formation of numerous grabens (Eger, Rhine, Limagne, Roanne-Montbrison, Bresse) from the late Eocene to the end of the early Miocene in and around the MC [START_REF] Merle | L'extension oligocene sur la transversale septentrionale du rift du Massif central[END_REF][START_REF] Michon | The evolution of the Massif Central Rift; spatio-temporal distribution of the volcanism[END_REF]. The development of this major graben system (West European Rift System; Figs. 1a andb) is accompanied by typical intraplate alkaline volcanism occurring either within the grabens or along their margins [START_REF] Wilson | Tertiary-Quaternary Extension-Related Alkaline Magmatism in Western and Central Europe[END_REF]. An important syn-rift magmatism event took place in the northern MC from late Oligocene to early Miocene [START_REF] Bellon | Datation absolue de laves d'Auvergne par la méthode potassium-argon[END_REF][START_REF] Chantepie | Le volcanisme basaltique miocène et pliocène dispersé dans la région de Clermont et sur le plateau des Dômes : étude pétrologique et géochronologique[END_REF][START_REF] Michon | The evolution of the Massif Central Rift; spatio-temporal distribution of the volcanism[END_REF]) at a time when sedimentation declined in the grabens [START_REF] Sissingh | Tectonostratigraphy of the West Alpine Foreland: correlation of Tertiary sedimentary sequences, changes in eustatic sea-level and stress regimes[END_REF][START_REF] Sissingh | Comparative Tertiary stratigraphy of the Rhine Graben, Bresse Graben and Molasse Basin: correlation of Alpine foreland events[END_REF] and where the crust was the thinnest [START_REF] Merle | L'extension oligocene sur la transversale septentrionale du rift du Massif central[END_REF][START_REF] Michon | The evolution of the Massif Central Rift; spatio-temporal distribution of the volcanism[END_REF]. This is why most of the late Oligocene volcanic activity is located near the Limagne graben (Fig. 1a) when almost no


Katia Oliver-Quelennec

François Bouchet
email: francois.bouchet@lip6.fr

Thibault Carron
email: thibault.carron@lip6.fr

Kathy Fronton Casalino
email: kathy.casalino@univ-lille.fr

Claire Pinçon
email: claire.pincon@univ-lille.fr

Adapting learning analytics dashboards by and for university students

Keywords: Dashboard, Learning Analytics Dashboard, Indicator, Co-design

Learning Analytics Dashboards (LADs) are becoming a key element in enabling learners to monitor their learning, plan and actually learn. However, LADs are sometimes not completely adapted to students, who are rarely involved in their design. Moreover, even when they are, the implemented LADs are often the same for all students, whereas previous works have shown the value of adapted LADs. Here we investigate which adaptations are requested by students, and attempt to identify which data and visualizations are suitable depending on the student's profile. More specifically, we consider dynamic profiles as students' expectations can vary over the course duration. By using LADs co-design sessions both online and on-site, we collected needs from N=386 university students from different disciplines and degree level, split in 108 groups (2 to 4 students). After a manual annotation, we identified a total of 54 types of data and indicators, divided into 12 thematics. Our first analysis confirmed some previous results, particularly on the use of peer comparisons that do not fulfill every student's needs. And we noticed other expectations according to the student's learning context or the academic period. Future work will benefit from these results to define a model of adapted LADs.

Introduction

Technology-Enhanced Learning is nowadays widely developed for both distance and face-to-face learning, which allows us to collect and analyze a large amount of traces of learning activities in order to help learners. By analyzing the data collected, we can understand how users learn with technology, develop new learning tools and offer a unique learning path for each learner. In the field of possibilities provided by learning analytics, Learning Analytics Dashboards (LADs) are a particularly popular approach to support learning. In recent years, several reviews have shown the growing interest in LADs [START_REF] Schwendimann | Perceiving Learning at a Glance: A Systematic Literature Review of Learning Dashboard Research[END_REF][START_REF] Jivet | Awareness Is Not Enough: Pitfalls of Learning Analytics Dashboards in the Educational Practice[END_REF][START_REF] Bodily | Review of Research on Student-Facing Learning Analytics Dashboards and Educational Recommender Systems[END_REF][START_REF] Scheneider | Use of Learning Analytics Interactive Dashboards in Serious Games: A Review of the Literature[END_REF][START_REF] Sahin | Visualizations and Dashboards for Learning Analytics: A Systematic Literature Review[END_REF]. But they also revealed the need for further research to design LADs showing a better grounding in learning sciences and learning theories, in particular due to the lack of specific visualizations for the activities of learning and teaching. Sahin and Ifenthaler [17, p.18] identified the need to involve stakeholders to define "which metrics are important" to them. Recent work by Ahmad et al. [2, p.66] has also concluded "that it is necessary to keep students and their opinions in the loop". In the case of students' LADs, previous works [START_REF] Roberts | Give Me a Customizable Dashboard: Personalized Learning Analytics Dashboards in Higher Education[END_REF][START_REF] Teasley | Student Facing Dashboards: One Size Fits All? Technology[END_REF] concluded that students needed adapted LADs with personalized displays. To meet this need, co-design tools have been developed to involve students in the design of LADs [START_REF] Prieto Alvarez | Co-designing learning analytics tools with learners[END_REF][START_REF] Gras | For and by Student Dashboards Design to Address Dropout[END_REF][START_REF] Dabbebi | User Centered Approach for Learning analytics Dashboard Generation[END_REF][START_REF] Hilliger | For Learners, with Learners: Identifying Indicators for an Academic Advising Dashboard for Students[END_REF][START_REF] Oliver-Quelennec | Can a Learning Analytics Dashboard Participative Design Approach Be Transposed to an Online-Only Context? 18[END_REF]. This approach is all the more important as, even if indicators and visualizations used in LADs can be helpful for the student, e.g. to be aware of their progress [START_REF] Jivet | Awareness Is Not Enough: Pitfalls of Learning Analytics Dashboards in the Educational Practice[END_REF], it can also have negative consequences, e.g. peer comparison in some contexts [START_REF] Tan | Learner Dashboards a Double-Edged Sword? Students' Sense-Making of a Collaborative Critical Reading and Learning Analytics Environment for Fostering 21st Century Literacies[END_REF][START_REF] Teasley | Student Facing Dashboards: One Size Fits All? Technology[END_REF]. The importance of involving students in the design of LADs having been demonstrated, we will focus in the next part on the content of these LADs, in particular on indicators and visualizations that compose them.

Previous works

Schwendimann [19, p.37] defines a Learning Dashboard as "a single display that aggregates different indicators about learner(s), learning process(es) and/or learning context(s) into one or multiple visualizations". Several studies considered existing indicators and their associated visualizations for LAD. Indicators' definitions vary according to the context. Glahn et al. [6,p.2] provides one that is quite generic: "Indicators are mechanisms to provide simplified information that are valuable to a task. With some background knowledge we can understand the meaning of an indicator without the need of knowing about the details of the underlying process or mechanism". In a review on LA indicators, Morais Canellas [13, p.107] defines a learning analytics indicator as "a calculated (quantitative or qualitative) measure [computability property] linked to a behaviour or an activity instrumented by the [traceability property] of one or more learners, visible to a user [visibility property] and which can be used to calculate other indicators". LADs are composed of several kinds of indicators and even if some general definitions exist, Ifenthaler [9, p.168] said "standards for indicators, visualizations, and design guidelines that would make learning analytics pedagogically effective are lacking". In the literature [START_REF] Hilliger | For Learners, with Learners: Identifying Indicators for an Academic Advising Dashboard for Students[END_REF][START_REF] Arriaran Olalde | Indicators needed to design a student dashboard from lecturers' perspectives: A qualitative study[END_REF][START_REF] Jivet | Quantum of Choice: How learners' feedback monitoring decisions, goals and selfregulated learning skills are related[END_REF][START_REF] Gras | For and by Student Dashboards Design to Address Dropout[END_REF], we can find studies describing various indicators used in students' LADs, but to the best of our knowledge, there is no consensus on a single exhaustive list of indicators for students' LADs or even on a single way to categorize them. Ifenthaler and Yau [START_REF] Ifenthaler | Reflections on Different Learning Analytics Indicators for Supporting Study Success[END_REF] worked on indicators to support success in predicting learning outcomes, and although some of them can be used in LADs, they focused on identifying students at-risk and did not attempt to cover all the expectations of students' LADs. Depending on the studies, LADs' indicators can be classified in different categories. We can use the aforementioned definition from [START_REF] Schwendimann | Perceiving Learning at a Glance: A Systematic Literature Review of Learning Dashboard Research[END_REF] to consider three categories: indicators about learner(s), learning process(es) and/or learning context(s). According to Jivet et al. [START_REF] Jivet | Quantum of Choice: How learners' feedback monitoring decisions, goals and selfregulated learning skills are related[END_REF], indicators used in LADs can be of two kinds: learning behaviour indicators, which provide information at the "learning process level", and content progress indicators, which provide information at the "task level". A study from Gartner [START_REF]Gartner Says Advanced Analytics Is a Top Business Priority[END_REF] on LA indicators classified them in four different types of analysis based on the nature of the performed analysis and which are increasing both in terms of value for the stakeholders and in terms of difficulty to compute them: descriptive (what happened?), diagnostic (why did it happen?), predictive (what will happen?) and prescriptive (what should be done?).

Some previous works to produce LADs for students involved them in different phases, from conception to prototyping. Hilliger et al. [8, p.118] identified that "the design of any dashboard should anticipate that its use could have a different effect depending on the context and the targeted user". With this approach, they defined indicators "relevant at the moment of choosing courses"[p.127] for a dashboard with a specific objective. This observation highlights the implicit need to consider indicators that are relevant at a given moment in time. For this reason, Gras et al. [START_REF] Gras | For and by Student Dashboards Design to Address Dropout[END_REF] developed an interactive dashboard which can be customized by first year university students, implying that "one size may not fit all" when it comes to students' LADs.

Overall we see that all these studies seem to define indicators and visualization(s) for students's LADs with specific objectives and an adaptation to a learning context. However there is a lack of works around the generalizability of LADs indicators (1) to different students in the same context or (2) to different learning contexts.

Objectives

In this paper, we try to investigate the need for LADs' adaptation through a different approach than in previous works. Namely, we seek to understand the needs for student LADs, not for an artificially imposed goal, but for a goal chosen by each student themselves. The underlying assumption is that students may be more at ease to propose their ideal indicators when they do so in a real context (a given course they are registered to) and for a goal that they deem relevant in the first place. Then using data from these numerous co-design sessions organized with university students, we tried to identify which indicators (and to a lesser extent, which visualizations) are spontaneously wished for by students depending on several elements of context such as their discipline, the study duration (short or long), their level (undergraduate or graduate), the moment in the semester (at the beginning of a course, during an ongoing course or towards the end of it, right before the final exam). More precisely, we attempted to answer the following research questions:

-RQ1: Is there a set of indicators for students' LAD that cover their expectations? -RQ2: Are there shared expectations of students for their LAD? I.e. are there frequently wished for indicators desired by a majority of students who have a same objective for their LAD?

-RQ3: Are there different expectations of students for their LAD, depending on their learning context (study duration, level) and/or moment in the semester according to the LAD's objective?

2 Material

To answer our research questions, we organised LAD co-design sessions using a co-design tool (PADDLE or ePADDLE method [START_REF] Oliver-Quelennec | Can a Learning Analytics Dashboard Participative Design Approach Be Transposed to an Online-Only Context? 18[END_REF]), online or in face-to-face sessions, with students in different contexts presented in table 1. In this paper we use data from a total number of 108 groups of 2 to 4 students (N=386 students overall). Each group was asked to design a LAD for a specific objective among 6 possible ones (monitoring, planning, communication, evaluation, evolution, remediation) that they were choosing themselves at the beginning of the session. A co-design session lasted an average of 91 minutes (SD = 25 minutes). For each LAD, we collected a list of indicators defined by students with a name, a description, one or more visualization(s) and a drawing of the final dashboard (see figure 1 for some examples of such dashboards).LADs produced by the students contain an average of 7.04 indicators or data (SD = 2.17).

Results and discussion

Overall, we listed 761 data and indicators with their visualization(s). After coding with generic titles, we obtained 54 indicators divided into 12 thematics using 24 different visualizations. Some thematics (monitoring, planning and communication) overlap with the objectives of the LADs. It is worth noting that not all of the 54 indicators wished for by students match the definitions of a LAD indicator from [START_REF] Jivet | Quantum of Choice: How learners' feedback monitoring decisions, goals and selfregulated learning skills are related[END_REF] or [START_REF] Morais Canellas | Métamodèle d'analytique Des Apprentissages Avec Le Numérique[END_REF], as students sometimes wish for information that is not directly linked to their learning but which they consider useful in order to plan their learning session (such as weather or personal agenda). Figure 2 shows all 54 indicators and data sorted by the percentage of groups that listed them. We can observe that no single indicator corresponds to all LADs (the most requested indicator, which is the grade, is asked for by 60% of students) and that there is a limited number of data and indicators desired by the majority of students.

We can see that the needs expressed are not limited to indicators, but students also ask for data, whether related to learning or not. We have chosen to keep indicators and data in our analysis because the LADs designed by the students are coherent sets. This is in line with Jivet's findings: "different tools should complement dashboards and be seamlessly integrated in the learning environment and the instructional design" [11, p.93]. In our study, students may have defined learning environments rather than LADs. Using the list of 54 indicators identified in RQ1, we looked for the 5 most wanted data and indicators by objective (monitoring, planning, communication, evaluation, evolution, remediation) and analyzed also the associated visualization chosen.

Results and discussion

We By comparing the desired data and indicators according to the LADs' objectives, we have identified some items that are shared by several learning contexts, but none of them is validated for all situations. Even if the grade seems to be wanted by a majority of groups, this data can be represented by different visualizations. This indicator is suitable for only 35% of LAD with a planning objective, perhaps because the planning objective groups together several sub-objectives such as planning one's work for the semester or planning one's revisions. The peer comparison indicator, which is often proposed in LADs, varies greatly, ranging from 20% to 72% of groups depending on the objective. This result confirms the need to adapt the LADs to the learning context and target, as identified in previous works. To go further, we should explore, for the same learning context (same student cohort, same study program, same year, same LAD objective), if there are shared expectations of students for their LAD.

RQ3: links between indicators and need profiles

Method

To identify a possible link between indicators and need profiles, we looked at the variation of expressed needs and selected the 5 data and indicators which varied the most for:

the study year: first, second and fifth year, the moment when the co-design session took place: at the beginning, the middle or the end of the semester.

this approach, additional analysis were conducted using SAS software (SAS v9.4, SAS Institute Inc., Cary, NC, USA). Categorical variables are presented as absolute numbers and percentages. Chi-square tests or Fisher's exact tests were used as they seem appropriate to compare proportions of a categorical variable. When a statistically significant result is found, Cramer's V was used to estimate the strength of association between the variables. A two-tailed type I error rate of 0.05 was considered for statistical significance.

Results and discussion

According to different learning context variables, we have identified various wishes by exploring the variations in the needs expressed by students.

Variation between study year According to the study year, indicators which varied most are presented in table 3. We identified statistically significant links for several thematic with some study year:

-1 st year students are less interested by indicators and data of the thematic information (p = 0.03 < 0.05, V = 0.22) with 0% vs. 23% of 2 nd and 5 th year students who wanted this kind of indicators (medium association). -1 st year students are also less interested in planning data than the others (χ 2 = 7.35, p = 0.02 < 0.05, V = 0.26) with 35% for 1 st year vs. 65% and 71% for 2 nd and 5 th year (medium association). -1 st year students are mainly more interested about data and indicators about project (p < .0001, V = 0.62) with 50% of 1 st year vs. >2% for the others (strong association). finally, data about personal life interested mainly 2 nd year students (p = 0.0057 < 0.05, V = 0.31) with 33% vs. 5% for 1 st and 10% for 5 th year (medium association).

1 st year students seem to expect less information to implement a learning strategy (coefficient, formative assessment). On the other hand, the are more interested with data and indicators about project management. In our study, 1 st year students came from two different academic programs and 2 nd and 5 th year from another academic program which could bias the results. The majority of first year students are in an IT course with a project-based pedagogical approach, which can explain the high interest for this kind of indicators. All 2 nd year students are pharmacy students and they have just passed the 1 st year of health studies, which means a very intense 1 st year. This could explain the importance of personal life for them, and they hope to find some leisure time. To refine this first result, data from several academic programs would be needed for each sample. And the type of study (duration, thematic, pedagogical approach) should probably also influence students' expectations. The year of study should be coupled with this information to refine this result.

Variation between moment in the semester

The results of the variations in students' expectations over time are presented in the figure 3. These results seem globally aligned with what one might naturally expect to observe. At the beginning, students need to plan the semester with basic information (timetable, evaluation's date, expected working time) and consider planning personal life. The information on planning decreases in the middle and at the end of the semester. They are replaced by two kinds of indicators, a learning one with the status of knowledge or skills (acquired and/or to be acquired) and a monitoring one the state of play and/or remaining work, probably to be ready for the exams. We have often seen LADs adapted to the learning context or/and adaptable by the students, but to our knowledge, no adaptation has been provided by the system according to the time. To go further to refine our results, adaptation over time by the system should be explored as an additional adaptation possibility.

Conclusion

As previous work has identified, LADs for students need to be adapted to the learning context and by students. We wish to pursue this line of work by investigating whether there were shared data or indicators between LADs with different objectives and whether it was possible to identify adaptation needs according to different variables linked to the learning context. Our results seem to indicate that there are some data and indicators more often desired by students, but in all cases, they remain specific according to the objective of the LAD. It seems that the needs of students change over time, depending on the time in the semester (beginning, middle and end). Students would like useful information to plan at the beginning of the semester and at the end of the semester, they seem to prefer indicators to assess the knowledge and skills acquired and the progress in the remaining work. This result opens new possibilities to adapt LADs according to time. Our next steps will be to try to define from these results an adaptive LAD model for students and to experiment on real LADs with students.

Fig. 1 .

 1 Fig. 1. Examples of LAD drawing produced by students

Fig. 2 .

 2 Fig. 2. Indicator and data sorted by the number of groups that selected them

Fig. 3 .

 3 Fig. 3. Variation over time (% of groups who requested these indicators broken down by moment)

Table 1 .

 1 The 7 different contexts of students participating in co-design sessions From the raw data, for each indicator defined by a group of students, we inferred a generic title to be able to compare the content of the different LADs. For each of the 108 LADs, we have listed indicators wished for by students and the associated desired visualization(s) they described or drew.

	Study	Study Period in the Study Co-design conditions Number Number of
	program	years semester	duration	of groups students
	Humanities 1 middle	5	face-to-face	2	4
	Pharmacy	2 beginning	6	face-to-face	23	91
	Pharmacy	2 end	6	online	34	121
	Pharmacy	5 middle	6	face-to-face	1	3
	Pharmacy	5 end	6	face-to-face	1	2
	Pharmacy	5 middle	6	face-to-face	29	107
	IT	1 end	2	online	18	58
				Total	108	386
	3 RQ1: set of indicators for students' LAD
	3.1 Method

  obtained 17 items presented in table 2. Almost all data and indicators listed in table 2 were whished for by groups of different kinds of study except those marked with *. We can observe that some data and indicators are shared by different objective, by different study program but, none is wished by all groups. For the 5 most wanted data and indicators, students expressed different needs in visualization for each data or indicators (between 5 and 17 different visualizations).

Table 2 .

 2 Compilation of the 5 most wanted data and indicators including ex-aequo for each objective (monitoring[MON], planning[PLA], communication[COM], evaluation[EVA], evolution[EVO], remediation[REM]) presented by % of groups concerned Data or indicator whished for by students from only one kind of study program.

					LADs' objectives
	Thematics Data and indicators	Rank	MON PLA COM EVA EVO REM
				N=15 N=54 N=10 N=11 N=12 N=6
		Inventory of time spent
	Monitoring	and/or time remaining State of play	7	20	28	20	55	17	0
		and/or remaining work	3	67	50	20	45	8	17
	Planning	Timetable To do list	2 6	13 47	57 31	50 20	27 9	33 8	17 0
	Communi-Help	23	13	4	20	0	0	33
	cation	Useful contacts *	17	0	13	40	0	0	17
		Course content	9	20	15	50	18	17	33
	Course	Description of the course, resources, and activities	11	7	24	20	9	33	0
		Knowledge requirements *	28	0	4	0	9	25	0
		Comparison with peers	4	20	28	50	73	58	50
		Formative assessment *	14	13	7	10	36	25	17
	Learning	Status of knowledge or
		skills (acquired and/or
		to be acquired)	8	53	13	30	27	25	0
	Method	Difficulties and adaptation * 15	13	17	10	0	8	33
		After evaluation	18	7	0	0	0	0	33
	Evaluation	Date	5	33	35	30	9	17	33
		Grade	1	80	37	70	91	83	100
	Personal life Private organisation,
		leisure and free time	10	7	33	0	0	25	0
	*

Table 3 .

 3 The 5 data and indicators which varied the most according to the study year presented by % of groups concerned

	Thematics Data and indicators	1 st year 2 nd year 5 st year
	Learning Comparison with peers	25	43.86	35.48
	Planning To do list	20	49.12	45.16
	Course	Course content	5	28.07	16.13
	Evaluation Coefficients	0	17.54	22.58
	Learning Formative assessment	0	15.79	19.35