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Mineral prospectivity mapping (MPM) aims at outlining areas with the highest mineralization hosting likelihood. The outcome of data-driven MPM approach highly depend on the spatial resolution and precision of the input cartographic datasets. Besides, the geological map has the inherent specificity of displaying 3D structures on a 2D surface map view; some structural configurations can usually lead to a misestimation of the relative proportion of the geological units, the faults or other features displayed in the map. From the Cell-Based Association (CBA), we develop here a new approach – the “Disc-Based Association” (DBA) – analyzing neighboring associations of cartographic features. First, disks entities are generated over a regular node grid covering the study area. Each disk discretize the overlapped data layers by integrating their information into a multivariate spectrum. Then, a Random Forest (RF) predictive model classify the multivariate spectrum from both mineralized nodes (e.g. whose associated disk contain a mineralization) and nonmineralized ones. As mineral concentration processes are inherently rare natural phenomena, we argue that all nodes except the mineralized one can be regarded as non-mineralized and thus used in the classification process. Predictivity scores are computed over the area based on the multivariate spectrum classification. This approach could allow the identification of several signature spectra associated to mineralization; which could be interpreted as several distinct metallotects / mineralization processes forming deposits in the study area. To test and evaluate its consistency, this new methodology is applied to prospectivity mapping of Sb along the Ibero-Armorican Arc (Western European Variscan Range). We infer this new data-driven approach applied to natural cases will improve prospectivity mapping and automatic recognition of new metallotects while giving new insights on the genetic processes forming deposits

International audience; The two main types of mineralisation in the Co-Ni-As Bou Azzer district, i.e., “contact” mineralisation” and “cross-cutting” structures have been re-defined based on new field, structural, textural and mineralogical observations. The main orebodies consists of elongated lenses of massive Ni-Co-Fe arsenide minerals. These lenses occur in a core of carbonate or siliceous gangue and are almost exclusively located along the contact between serpentinite and a quartz diorite intrusion. Vein systems, cross-cutting the different lithologies, are ore-bearing only along segments in contact with the serpentinite and/or the massive mineralisation. The two orebody types share a rather similar mineralisation history, starting with a Ni-rich arsenide stage (mainly expressed within the massive mineralisation), followed by a massive Co-arsenide stage recognised in both mineralisation styles, and ending with Fe-rich arsenide and base metal sulphide stage.Detailed field observations, microstructural, tectonic, textural and mineralogical analyses led us to propose a genetic model for the Bou Azzer ore district in which massive mineralisation was formed by alteration and transformation of previously formed breccia levels composed of serpentinite (transformed to gangue) and magnetite/spinel (transformed to Co-Ni arsenide minerals) fragments. Inversely, a tectono-hydrothermal event controlled by a NE oriented transtension generated the vein system, associated certainly with partial leaching and reconcentration of metals from the massive mineralisation because veins are principally mineralised when crossing massive orebodies. We discuss a possible temporal continuum between the two mineralisation styles: massive mineralisation, coeval with serpentinisation (serpentine neoformation), is related to the transformation of brecciated lenses and vein mineralisation is formed as an infill of large fractures during transtensive tectonics. This model has significant tectonic implications, because serpentinite breccia lenses, favourable high-permeability environment for the massive mineralisation formation, can be compared to ophicalcic rocks developed in a context of mantle exhumation by detachment. Two types of textures can be differentiated within the massive mineralisation: i) Brecciated Massive Mineralisation, developed in the core of ophicalcic levels, and ii) Laminated Massive Mineralisation, supposed to form within ancient mylonitic serpentinite levels corresponding to intensive deformation zones. Although the geodynamic significance will not be addressed in this article, we propose and discuss an alternative model in which the presence of exhumed mantle rocks allows the formation of specific massive arsenide deposits.

南岭地区中-晚侏罗世含铜铅锌与含钨花岗岩的矿物学和地球化学特征截然不同. 含铜铅锌花岗岩主要为准铝质含角闪石的花岗闪长岩, 具有较高的CaO/(Na2O+K2O)比值、LREE/HREE比值和 δ Eu值, 较低的Rb/Sr比值, Ba、Sr、P、Ti轻微亏损, 分异演化程度较低. 含钨花岗岩为高分异演化的过铝质花岗岩, 其CaO/(Na2O+K2O)比值、LREE/HREE比值和 δ Eu值较低, Rb/Sr比值较高, Ba、Sr、P、Ti强烈亏损. 含铜铅锌花岗岩主要形成于155.2~167.0Ma, 峰值为160.6Ma, 含钨花岗岩主要形成于151.1~161.8Ma, 峰值为155.5Ma, 两者存在约5Ma的时差. 在湘南铜山岭含铜铅锌和魏家含钨花岗岩系统研究基础上, 结合南岭地区中-晚侏罗世含铜铅锌与含钨花岗岩的对比, 提出了两类含矿花岗岩的成因模式. 古太平洋板块俯冲导致软流圈上涌和玄武质岩浆底侵. 底侵玄武质岩浆加热促使下地壳镁铁质角闪岩相基底首先发生部分熔融, 形成与铜铅锌矿化有关的花岗闪长质岩浆. 随着玄武质岩浆底侵, 中-上地壳富白云母变质沉积基底发生部分熔融, 形成与钨矿化有关的花岗质岩浆. 花岗岩源区成分的差异导致花岗岩成矿专属性不同, 源区部分熔融的时间先后导致了含铜铅锌与含钨花岗岩之间存在5Ma左右的时差.

International audience; The hydrothermal native element-arsenide mineralization (five-element) type comprises native Ag and/or native Bi as well as Ni-, Co-, and Fe-arsenides and-sulfarsenides. Due to the current surge in Co-demand, this mineralization type has regained recent economic interest. Thus, it is of interest to further understand the paragenetic and possible spatial relation of Co-bearing minerals and the formation mechanism/process of this mineralization type. This is achieved through an extensive literature review in combination with newly calculated stability relations. The mineralization is host rock independent, but spatially linked to sources of reducing agents (as this is the cause of precipitation). This reduction process results in a thermodynamically controlled characteristic Ni- Co- Fe-diarsenides sequence, as well as a transition from native elements to mono-to di-arsenides. The temporal Ni  Co  Fe trend has also been described to occur on a special scale, and since it is ubiquitous, it may be used as a tool in constraining Co rich sections of a deposit. The formation of this mineralization is, however, not only thermodynamically, but also kinetically controlled, as is evident by the abundant dendritic textures. Kinetics favor a sulfate-sulfide disequilibrium which enables an aqueous sulfide poor system that allows for arsenide formation.

International audience; The French Massif Central (FMC) forms the hinterland of the west-European Variscan belt and was subject to numerous tectonic and metamorphic events from Devonian to Permian times. The accreted tectonic units belonging to Gondwana and Laurussia were variably involved in subduction, nappe stacking and syn-to post-orogenic extension. Besides, plutons and migmatites showing syn-collision crust melting are very common in the Variscan belt. Such orogenic evolution implies that the resulting finite structure likely reflects the interference between fabrics formed at different stages of the orogenic cycle with different degrees of overprinting, depending on e.g. the spatial strain gradients, lithologies, structural level or partial melting grade. We present a model of finite strainfield of the western FMC based of the analysis/interpolation of ductile and brittle fabrics, at regional to local scale, using geostatistics. Ductile fabrics within autochthonous units and syn-collisional plutons are poorly disturbed and reflect the transition from syn-thickening to extensional lateral flow of the partially molten mid-lower crust. In contrast, allochtonous units are affected by numerous perturbations including polyphased ductile shearing, folding and faulting inducing local bloc tilting and rotations. Taking into account the overprint of late tectonic events, we show that early fabrics related to High Pressure metamorphism or nappes' stacking have suffered intense reorientations. The finite trend of the related lineations L1 must be treated with extreme caution and may not reflect the original direction of stretching and shearing that occurred during the initial compressional stages. Taking into account i) the spatial distribution and amount of reorientation of these D1 fabrics and ii) the deconvolution of these disturbances, we propose that:-The high dispersion of lineation trend can be simply explained by passive rotations, during late isoclinal folding, rather than two superposed tectonic phases, as previously inferred.-The allochtonous units formed one single tectonic unit.-This D1 event looks related to the exhumation of the subducted continental crust due to partial melting-The formation of Variscan orogenic prism in western FMC only results of continuous south-directed thrusting rather than a switch from NE-SW to NW-SE thrusting.

International audience; The W-Sn veins of Panasqueira are connected with a massive quartz-muscovite greisen cupola. This greisen results from interactions between granitic rock and acid Sn-W hydrothermal fluid, which causes the destruction of feldspars of the Panasqueira granite. Greisenisation can constitute an important factor of control on fluid flow, and its role on metal transport remains to be established. Mineral reactions of greisenisation involve a decrease of the rock volume and thus an increase porosity (~6%). Consequently permeability increases significantly (10-20 to 10-17 m²) enhancing fluid flow in the greisen cupola and promoting further hydrothermal alteration and transport of metals. Finally a part of the mineralization is trapped in this porosity, with precipitation of cassiterite and sulfides. Therefore, Sn-W fluids are able to generate their own pathways in initial impermeable granite via greisenisation reactions.

International audience; Partitioning of chalcophile and siderophile elements between sulfide and silicate melts (Dsul/sil) has been largely investigated, mainly through experiments at mantle conditions and under low oxygen fugacities (fO2 < FMQ-1). However, the formation of magmatic sulfide ore deposits occurs at crustal conditions and most likely at higher oxygen fugacities.We present a new experimental set of partition coefficients for Ni, Cu, Pd, Ag, Pt and Au obtained at crustal conditions relevant to the formation of Noril’sk ore deposits (Siberia). Experiments were performed in internally heated pressure vessels equipped with a rapid quench device at 1200 °C and 700 MPa, under variable fO2 (between FMQ-2 and FMQ+1). The specificity of this study is that (i) a natural, metal-undoped composition was used as starting material (a picrite from Noril’sk-1 intrusion), and (ii) the sufide melt segregated directly from the silicate melt, due to S addition. Magmatic textures were generally well preserved owing to the rapid quench.The sulfide melt – silicate melt partitioning of metals can be expressed by an exchange equation of the form: MO + 0.5 S2 = MS + 0.5 O2. According to this equation, Dsul/sil must be correlated with log fS21/2 - log fO21/2, as generally shown in the litterature. However, such a clear correlation is hidden by the large variability in experimental conditions (T, P, composition of the sulfide and silicate melts). We therefore investigate the effect of each intensive parameter in order to present a new model applicable to the formation of magmatic sulfide ore deposits.

National audience; The Anti-Atlas belt is well known for its numerous copper deposits.It displays also a complex geological, metallogenic andtectonic history which is challenging for mining companies in orderto better understand and prospect these Cu-deposits. In theBou Azzer-El Graara inlier, these deposits are hosted as well withinthe Precambrian basement as within the Neoproterozoic to Paleozoiccover. This study based on mapping, structural, mineralogy,textures and micro-textures observations present a synthesis ofCu-deposits at this inlier scale In this Neoproterozoic to Paleozoicsedimentary cover, two types of mineralizations are distinguished:one is related to local folds and faults and another one associatedwith a deformation localized in specific stratigraphic levels at thebase of the cover. Geological and mineralogical studies showedthat both Cu-ores types are controlled by the same hydrothermalevent associated to the Variscan orogeny. In the Precambrianbasement, massive copper sulfides lenses are present at the intersectionbetween regional pyritic beds or black shales and brittlefaults potentially associated with the late Panafrican deformation.Another kind of Cu-deposits is spatially associated with Panafricanshear zones, which showed ductile and brittle deformations. Thesemineralizations seem to be linked to the late brittle deformationthat re-used the ductile shear zones inherited from the Panafricanorogeny. During the Variscan compression, the reactivation, ofbasement-inherited Panafrican structures controlled the deformationresponsible of mineralization in the cover. In summary, coppermineralizations are closely associated with a brittle deformation,posterior to the ductile Panafrican deformation in the basementand synchronous with the Variscan orogeny in the cover. The metallogenichistory of copper in the Bou Azer-El Graara inlier canbe depicted through, at least, two models: (i) a two-stage model,with a first late Panafrican hydrothermal event, responsible for thebasement-hosted Cu-bodies and a second Variscan event, yieldingCu-deposits hosted in the cover. (ii) A single metallogenic phase,during Variscan deformation, that mineralized both the basementand the cover. Works in progress try to assess the relevance ofthese models at the Anti-Atlas scale.

International audience; The renewal of interest in Zn-Pb non-sulphide ores has been induced by mineral processing improvement and leads to new exploration and mining projects in the world. Although the mineralogy is often precisely known, and despite several studies linking ore deposition to regional tectonics, absolute dating of non-sulphide stages is rare and structure of ore bodies was largely disregarded. Geochronological data from non-sulphide ores are essential to timely constrain alteration episodes and to insert supergene ore genesis in the climate and tectonic evolution of the metallogenic province. The access to internal organization of ore could reveal post-mineralization episodes related to supergene evolution. Thus, a rock magnetism study combining anisotropy of magnetic susceptibility (AMS) and palaeomagnetism was performed on four non-sulphide deposits from the Moroccan High Atlas. AMS generally shows similar horizontal magnetic fabrics for ores and the clayey and carbonaceous internal sediments filling karstic cavities. The palaeomagnetic directions of ores and internal sediments are compatible, and the calculated poles are consistent with the last 30 Ma of the Africa apparent polar wander path, with an upper age at 0.78 Ma. The proposed three-step scenario is placed within the evolution of the Moroccan High Atlas belt. Deposition of primary sulphides is contemporaneous with opening of the Tethyan and Atlantic oceans. During the Tertiary, intracontinental deformation gave rise to the High Atlas fold-and-thrust belt and to regional uplift. Finally, Zn-Pb sulphides hosted in carbonates experienced oxidation under an arid climate to form karst-related Zn-Pb non-sulphide ores. These promising results pave the way for an efficient method to constrain the internal fabrics and age of Zn supergene deposits.

International audience; The Troodos ophiolite in Cyprus, formed in a Cretaceous (92 Ma) supra-subductionzone setting, is considered to be one of the best-preserved ophiolite complexes in theworld. This ophiolite hosts several dozen Volcanogenic Massive Sulfide (VMS)deposits that are up to ~20 Mt in size and were exploited for both sulfur and base metals.VMS deposits have been shown to originate through leaching of metals duringhydrothermal alteration of the sheeted dike complex. A recent study [1], has performedmass balance calculations by considering the protolith composition and the secondarymineral assemblages, and thus was able to quantitatively constrain the release of basemetals from the altered sheeted dikes. These authors report bulk metal contents ofbasaltic andesite glass protoliths and variably altered facies rocks from the epidositezone of the Troodos ophiolite, and suggest that Cu was totally lost during the earlystages of alteration owing to complete breakdown of igneous sulfides originally presentin the protoliths, whereas the release of other base metals (Ni, Zn, Mn, Co) towardsmineralizing fluids was controlled by the secondary mineral assemblage, i.e., therelative abundance of epidote and chlorite ± amphibole. This interpretation stresses therole of silicate minerals in the redistribution of metals during hydrothermal alteration ofthe sheeted dike complex, and contrasts with the common assumption that accessoryphases, such as sulfides, control base metal concentrations within mineralizing fluids inVMS systems.Here we propose to test this hypothesis by providing measurements of the metalcontents of sulfide minerals contained in various lithologies from the Troodos ophiolite.We report laser-ablation ICPMS analyses of 14 base and precious metals (Ti, Cr, Mn,Co, Ni, Cu, Zn, Zr, Mo, Ag, W, Pt, Au, and Pb) in sulfides present in samplesrepresentative of different stratigraphic levels and chronological stages of thehydrothermal alteration within the ophiolite complex. Preliminary results show a largevariability of metal concentration and behavior depending on the lithology. Igneoussulfides present in least-altered metabasalts from the upper part of the crust are notablyenriched in Co, Ti, Cu, Pb, Mn and Ag. They likely contain most of the bulk metalbudget of the primary lavas. Importantly, numerous sulfides are still preserved in theepidotized sheeted dike complex, and remain enriched in Co, Ti, Pb, Mn (while Cu andAg appear to have been remobilized). The sulfide-bearing quartz veins corresponding tothe discharge upwelling of hydrothermal fluids show very low metal concentrations,with the exception of Ni, Pb and Cu. Finally, the massive sulfide deposits are made ofCu-, Zn-, and Co-rich pyrite and Pb-, Mo-, Zn- (and Ti-) rich chalcopyrite. Theseobservations suggest that sulfides may have a significant role in controlling theprogressive release of some metals during the different steps of hydrothermal alteration,and need to be considered in conjunction with the secondary silicate minerals.[1] Jowitt S.M. et al. (2012). J. Geochem. Explor., 118, 47-59.

International audience; Tin mineralization in Achmmach deposit (NE of Moroccan Central Massif) is associated with tourmaline-rich alteration halos and faults, within N70 shear zones, hosted in sandstones and metapelites of the Upper Visean-Namurian. Such deposits were reported as late-Variscan in age and related to the emplacement of late orogenic granite not outcropping in the studied area.From field constraints, it appears that the late Variscan phase is marked by a transition from transpression to extension with conditions of deformation evolving from ductile to brittle environments. During the transpressive phase (horizontal shortening direction roughly trending E-W), pervasive tourmaline is deposited under the form of metasomatic halos around fractures in the upper levels relative to the deep batholith. This hydrothermal activity is coeval with ductile shear zones within a large corridors trending N70. Tourmaline-rich alteration appears as a hardening stage contributing to the modification of the tectonic style of rocks. Thereafter, a strong brecciation occurs in response of re-using and re-opening of the strike-slip structure. The result is (1) the formation of dextral (N070, N020) and sinistral (N120) shears, and (2) the circulation of fluids within early tourmalinites and formation of tourmaline-rich breccia. Subsequently, during the late orogenic extensional phase, tourmalinite breccias reopened as normal faults acting as overpressure fluid pathways for developing other breccias and veins. Such event is marked by deposition of tin mineralization i.e., cassiterite followed by sulphides, and then fluorite and carbonates at the end.From analysis of the shear-zone structure and superimposition of tourmalines and tin mineralization in the same structures, it is possible to suggest a structural control continuum. Such control is well expressed during metasomatism and deposition of hydrothermal tourmaline under the transpressive phase. Thereafter, under the extensive phase allowing open-space, tin-mineralization were trapped.This study has been supported by AI MA/09/210

Les circulations hydrothermales sont le vecteur d'échanges thermiques et chimiques d'importance majeure entre la géosphère et l'hydrosphère. Un grand nombre de concentrations métalliques et minérales sont liées à ces transferts et les modèles métallogéniques évoquent très souvent des directions de paléo-écoulements entre différents réservoirs géologiques. Cependant l'hydrodynamique des systèmes hydrothermaux reste mal connue et les directions d'écoulement sont peu contraintes par les données de terrain. Mes travaux de thèse sur le gisement à F, Ba et Fe de Chaillac ont montré que les textures des formations hydrothermales permettent d'obtenir une information locale sur les directions des paléoécoulements. A partir de cette observation, mes recherches ont été orientées suivant trois axes complémentaires. (i) La modélisation de la croissance cristalline d'un monocristal dans un fluide en écoulement : plusieurs modèles ont été développés, le plus performant consiste à résoudre numériquement les équations de Navier Stokes et l'équation de transport autour d'un cristal polyédrique (hexagonal). Dans ce modèle simple de croissance cristalline les cinétiques de surface sont négligées devant les cinétiques de diffusion volumique. Les flux chimiques simulés sur la face amont sont supérieurs aux flux de la face avale et leur rapport augmente avec la vitesse de circulation du fluide. (ii) La croissance expérimentale de monocristal d'alun dans un fluide en écoulement a permis de vérifier que la croissance est plus rapide pour les faces amonts que pour les faces avales, le rapport des flux augmente avec la vitesse mais diffère significativement du modèle numérique. L'hypothèse d'une croissance sans influence des processus de surface conduit à surestimer le rapport des flux. (iii) Les études de terrain sur des gisements hydrothermaux ont été menées, en exploitant les modèles développés afin d'évaluer in situ l'hydrodynamique des paléoécoulements. Les premières études ont consisté à tracer les directions d'écoulement des paléochamps hydrothermaux à partir des fabriques magnétiques. Dans les formations riches en magnétite, les résultats suggèrent que la forme allongée des grains marque le sens de l'écoulement comme le modèle et les expériences l'ont prédit. Les fabriques magnétiques mesurées dans les formations carbonatées, et riche en goethite laissent penser que la croissance cristalline est organisée suivant les lignes de courant. Ce dernier résultat rend nécessaire le développement de nouveaux modèles dans lesquels la croissance de plusieurs cristaux doit être considérée dans la porosité de la roche. Enfin, l'utilisation de la variation des rapports des flux en fonction de la vitesse d'écoulement a été utilisée pour estimer des vitesses dans une tourmalinite formée au contact d'un sill leucogranitique. Les rapports des bandes de croissances permettent d'estimer une vitesse minimum d'écoulement locale et instantanée de l'ordre de 10-3 m/s, ce qui est bien supérieur aux vitesses couramment proposée dans la littérature, celles-ci étant calculées à partir de modèles macroscopiques donnant des vitesses moyennées en temps et en espace.

21-23 mai 2008; L'Anisotropie de la Susceptibilité Magnétique (ASM) est utilisée depuis une trentaine d'années pour déterminer la fabrique des roches (Hrouda, 1982 ; Tarling et Hrouda, 1993). Elle est aussi largement utilisée lors de travaux de géologie structurale en particulier ceux relatifs à la détermination des structures des plutons granitiques (Talbot et al., 2005). L'objectif de cette communication est de montrer, à partir de deux études de cas, comment le couplage entre l'ASM et l'analyse texturale permet de retracer le(s) trajet(s) de circulation des paléo-fluides.

International audience; As in several other AMS studies, the main direction of the magnetic lineation analysed in Part I of this work, as well as crystal elongation, have been found to be roughly aligned with the direction of the surrounding flow. In order to explain the mechanisms responsible for such crystal shape anisotropy in a hydrodynamic context, we derive a mathematical model based on Falkner-Skan self-similar boundary layers at high Reynolds numbers. The model allows calculating local growth rates out of diffusion processes in the concentration boundary layer for crystal faces orientated arbitrarily in the range 90° to -18° with respect to the flow direction, and for any flow velocity. Hence, our work generalizes rationally previous attempts already done in the case of a flow parallel to the crystal face. This crystal growth model is applied to a natural case of calcite growth rate in 2D section perpendicular to the axis. The reconstructed calcite growth reproduces the texture of a natural case observed in Part I, although the local Reynolds numbers are quite low. This approach may be applied for various geological settings, from deep metasomatism to flowing on the earth surface.

Numerous studies and observation have been made on the influence of flow to crystal growth in solution. Previous observations of growth bands in natural galena suggests that upstream crystal faces possess a higher growth rate (Kessler et al. 1972). Flow control on crystal growth is complex and different approaches have therefore been considered. Studying at very thin scale focuses on crystal face behaviour with effect of flow on crystals defects (e.g. step bunching; Chernov 1992 and 2004). At crystal scale several observations and models propose to link crystal shape and growth kinetics to fluid flow. Experiments showed that in case of volumic diffusion, the bulk crystal growth rate is proportional to the inverse of the square root of the flow kinetics (Garside et al. 1975). By experiments on ammonium-dihydrogen phosphate (ATP) (Prieto & Amoros 1981) and This work concerns a very simple and well-defined geological situation: calcite-rich precipitate formed in a horizontal pipe channelling hot water (82°C) of hydrothermal spring in Chaudes-Aigues city (French Massif Central). Shape preferred orientation statistics were performed on 563 calcite sections in the (0001) calcite plane, shows elongated shapes with a general orientation parallel to the pipe axis. The mean shape orientation is the average of two distinct sub-populations that deviated slightly from the pipe axis. Observation on calcite shapes and the direction of the magnetic lineation are coherent, and suggest that it is possible to track hydrothermal paleo-circultion using magnetic lineations and petrographic fabrics. The proposed crystal growth model is based on the work of Gilmer et al. (1971). These authors consider two kinds of processes: diffusion of solute through a volume of unstirred liquid (i.e. boundary layer) to the crystal surface and reactions at the surface leading to the incorporation of molecules in the lattice. When the boundary layer is thicker, the diffusion process becomes slower and controls the crystal growth rate. Thus, it is possible to establish a quantitative link between growth rate and fluid velocity. Such equation has been only demonstrated in the case of crystal face parallel to fluid flow (Carlson 1958; Gilmer et al. 1971). This work proposes to estimate crystal growth rate in flowing solution based on diffusion through the boundary layer thickness. This latter is defined by a combination of diffusion law with fluid dynamical equation simplified for high Reynolds number and for crystal faces orientated from 90° to –18° as function of the flow. The proposed growth rate equation depends on two main parameters: (a) the position along the face and (b) the angle made by flow with the crystal face. The growth rate equation is proportional to the square root velocity and is in agreement with the Garside et al. experiments (1975). More over, this model is applied to calcite growth rate in 2D section perpendicular to the axis. The calcite shape reconstruction is similar to the texture observed at Chaudes Aigues. The differential growth rate with exposition allows to explain the elongated shape of the calcite crystal observed in the pipe. This approach may be applied for various geological setting, from deep metasomatism to flowing on the earth surface.

Chaillac est un système hydrothermal fluo-barytique complet, avec sa racine quartzo-fluorée et son griffon à gœthite, fluorine et barytine. Une partie des fluides circulant dans la faille (le filon du Rossignol) émerge à la surface d'un bassin détritique continental pour constituer les plateures et imprégner les formations perméables. L'abondance de la gœthite indique des conditions de dépôt oxydantes, une reconcentration avec individualisation d'une cuirasse latéritique pouvant avoir été occasionnée au Sidérolithique. Il n'y a pas d'équivalent actuel connu de système hydrothermal de ce type.

The textural description of a solid can be seen as a two stages job. The first one consists in determining the mineralogical composition and the size of the components. Information collected during this step will be named Granularity Parameter (GP). The second stage is a study of the spatial distribution of the components, called below Distribution Parameter (DP). The proposed method quantifies GP and DP by respectively constitution heterogeneity (HC) and distribution heterogeneity (HD). HC and HD are functions defined by P. Gy, 1982 and 1988 in his “Theory of particule material sampling”.