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International audience; In heap leaching, agglomeration of clay rich ores is commonly used and may prevent plugging phenomenawithin heaps, but is not always successful. In order to better understand the heap leaching process of uraniumore agglomerates, a multi-scale approach, based on 10-cm and meter-scale columns, was used to achieve aRepresentative Elementary Volume (REV) of packed agglomerates. Flow rate and agglomerate size distributionwere found to have no impact on the ore leaching kinetics. An increase of the sulfuric acid content of theleaching solution caused a slight increase of uranium extraction. Meter-scale tests indicated that scaling up hadno significant influence on extraction kinetics. Some tests have also shown that column porosity and permeabilitydecreased during irrigation and with the heap depth. This led to the occurrence of plugging. X-ray tomographyanalyses on clogged sections of the column revealed that this phenomenon arises from agglomeratemechanical degradation. In addition, an integrative numerical model of the leaching of the meter scale columnof agglomerates was built, combining flow and reactive transport equations where the effective reaction termwas directly inferred from the REV experiments. An excellent agreement was observed with the column tests.

Jurassic carbonate strata in the eastern Paris Basin exhibit several generations of faults, tension gashes and stylolites. Although their relative chronology can sometimes be determined according to cross-cutting relationships, the duration of major deformation phases and their influence on fluid flow and carbonate cementation are still uncertain. This contribution aims to clarify the timing of brittle deformation and associated calcite cementation. Tension gashes filled by calcite in Jurassic carbonates were sampled in outcrops and boreholes and dated through U–Pb geochronology. Almost all the sampled fractures were cemented during the Cenozoic period. Continuous deformation spread from c. 50 to 30 Ma. Tension gashes oriented N10° to N20° dated at 48–43 Ma show the main Pyrenean contractional stage. A second set of calcites were dated at c. 35–33 Ma and document a Late Eocene – Oligocene extension. A transition from the compressional to the extensional regime is expressed by tension gashes dated between 43 and 35 Ma. Finally, tension gashes oriented N150° to N175°, dated between 32 and 18 Ma, may result from the propagation of the horizontal stress generated by the Alpine orogen or by late Pyrenean deformation. Clumped isotope thermometry on five samples revealed both low crystallization temperatures (from 27 to 53 °C) and the meteoric origin of calcite-precipitating fluids. Our research therefore documents a continuous fracturing from Ypresian to Rupelian times, and less expressed brittle deformation during the Miocene period.

International audience; Sedimentary strata are essential archives of the past conditions of the earth, and host significant natural resources in the subsurface. However, inferring the features of strata at depth (e.g., geometry, connectivity, physical or geological properties), remains a challenge prone to many uncertainties. Classically, the layers and their geometry are first interpreted from boreholes, geological outcrops and geophysical images, then layer properties can be addressed with geostatistical techniques and inverse methods. Theoretical models considering horizon depth uncertainty have been proposed decades ago, and geostatistical simulation can sample petrophysical uncertainties, but these approaches leave the number of layers fixed and are rely on conformable layering assumptions which are seldom met. We review some recent developments in well correlation in the frame of relative chronostratigraphy, which addresses the problem of locating potential gaps in the stratigraphic record. We also present some first results of the integration of the number of layers in inverse problems using a reversible jump Monte Carlo method. These two elements open interesting perspectives to jointly address topological, geometrical and petrophysical uncertainties at multiple scales in sedimentary basins. Although such uncertainties can have significant impact on quantitative geological and geophysical model forecasts, many computational challenges still lie ahead to appropriately sample uncertainties. Harnessing these challenges should open the way to finding, on a case-by-case basis, the suitable level of detail between detailed stratigraphic architectures and effective medium representations.

International audience; Seven sections, covering the upper Albian to lowermost Turonian, have been correlated from full-marine to continental-dominated deposits across a passive margin, along a transect 425 km long, from the present-day Atlantic coast to the ``Pre-African Trough'' between the Anti-Atlas and the High-Atlas. The thickness of the Cenomanian succession changes from around 500 metres in the fully marine sections to 250 metres in mostly continental facies in the western High-Atlas, about 150 km updip, to a few tens of metres in the Bou Tazoult area. The strata thicken again eastwards into the Pre-African Trough where they can be traced without major facies changes to the Kem Kem embayment and to the Bechar area in Algeria. Over all this eastern area, continental facies are overlain by the fully-marine shallow-water deposits of the Cenomanian-Turonian boundary interval. A first major conclusion is that fluvial aggradation in high-frequency transgressive-regressive sequences is coeval with the seaward-shift of the shoreline, in accordance with the genetic sequence stratigraphic model of GALLOWAY (1989). Both the flatness of the depositional profile and the corresponding very low energy of the marine environment during the transgressions account for the blanket of red continental clays on top of marine facies in updip depositional sequences, which is then preserved under the marine transgressive surface of the next sequence. A second major conclusion is that the high-frequency transgressive-regressive (T-R) sequences do not look like classical parasequences bounded by transgression surfaces. They usually exhibit a surface created by a sea-level fall within the regressive half-cycle. This is interpreted in the following way: regressions did not operate through a regular seaward-shift of the shoreline, but through stepped sea-level falls. The very low slope of the depositional ramp is thought to have enhanced the sequence stratigraphic record of such stepped regressions. Short-term, high-frequency sequences are organized into medium-frequency T-R sequences (seven in the Cenomanian) which show an overall aggrading and slowly retrograding pattern along the whole transect. Comparisons with other basins show that medium-frequency sequences do not fit the third-order depositional sequences described elsewhere, casting doubts about a eustatic mechanism for their deposition.

The Polish Kupferschiefer, with sediment-hosted polymetallic (Cu, Ag, Au, PGE) deposits, is one of the most important sources for copper and silver in the world. Within the framework of the ProMine project, the Lubin region (southwestern Poland), was selected for modelling the geological formations in 3 dimensions and 4 dimensions in order to better understand the distribution of the Cu-Ag mineralization, and possibly to define new potentials. The restoration—decompaction methodology available in gOcad, coupled with PetroMode 1D, were used to reconstruct the temperatures, pressures, hydraulic fracturing favourable conditions, and oil and gas maturation during the burying history of the Lubin Kupferschiefer, Southwestern Poland basin. Conditions for hydraulic fracturing were identified for the base of the Zechstein shales, during an inversion phase at the Late Cretaceous-Early Palaeocene. This Late Cretaceous up lift yields the conditions for hydrothermal recirculation of mineralizing brines explaining the location of Cu (Cu-Fe) sulphides ores in the area. The Zechstein evaporite series played a role of impermeable cover confining the hydrothermal fluids in the lower Zechstein series. The 4D restoring-decompacting modelling allows for reconstructing the burial, deformation and natural hydro-fracturing history of intra-basin sediment-hosted ore deposits. In the Lubin region, the obtained results show a good agreement between the spatial hydro-fracturing index and the emplacement of the Cu (Cu-Fe) sulphides exploited today.

International audience; The Bayinwula roll front-type uranium deposit is hosted in sandstones of the Early Cretaceous Saihan Formation deposited during the postrift stage of the.Erlian basin, in northeast China. The present study aims to characterize: (1) the roles of sulfate-reducing bacteria and (2) the roles of Fe-Ti oxides in the genesis of the Bayinwula deposit. Drill cores of the host sandstone have been investigated with emphasis on petrographic observations, whole-rock geochemistry, and geochemical and/or mineralogical study of Fe-Ti oxides, iron disulfide, uranium minerals (EMP, LA-ICPMS), and organic matter (rock-eval pyrolysis). The delta S-34 value has been measured in situ by SIMS on the different generations of iron disulfide. Within regional sandstones, preore uranium enrichment (U-mean = 30.4 ppm in whole rock) was identified on altered Fe-Ti oxides (36.5% of the whole-rock U content) and constitutes a major source of uranium for the mineralization. Petrographic observations and rock-eval data indicate that organic matter occurring in the host sandstone is mainly inherited from land plants and corresponds to type III or type IV kerogens. Organic matter fragments disseminated in sandstones may also contain significant preore uranium concentration. Framboidal and collomorph ore-stage iron disulfides have moderate to high concentrations of As, Ni, and Co and have a light sulfur isotope signature characterized by delta S-34 values from -30.5 to -7.5 parts per thousand, suggesting that sulfur originated from bacterial sulfate reduction, which was mainly responsible for (1) the liberation of U from Fe-Ti oxides and organic matter, (2) the generation of ore-stage iron disulfides, and (3) the production of a secondary H2S-rich reducing barrier involved in the reduction of U(VI) and the precipitation of U(IV). Uranyl and sulfate ions were transported through the host sandstone by low-temperature oxygenated groundwater and U(IV) was precipitated at the redox front as P-rich coffinite and ningyoite, dominantly as replacement of ore-stage iron disulfides which have partly to totally replaced organic matter and Fe-Ti oxides. Therefore, the combined mineralogical, geochemical, and isotopic characteristics of the Bayinwula roll-front uranium deposit support the theory that biogenic processes have widely contributed to the genesis of the uranium mineralization.

This chapter aims to summarize the investigation on the selective dispersion and characterization of particle mixture systems in concentrated suspensions to better understand their current status and to extract the useful information for advanced particle processing. Dispersion of fine particles is a challenging problem. The first difficulty is to achieve a long-term stability of particle dispersions, avoiding coagulation after physical or chemical treatment. The second difficulty is to selectively disperse/liberate particles along grain/material boundaries for promoting the subsequent process (e.g., particle self-assembly and mineral separation). The first half of this chapter, thus, provides a brief overview of this subject and also introduces a new way of achieving selective fine particle dispersion by an electric field application. In terms of characterization, a limited number of studies have been performed on the characterization of the particle-particle interaction in mixture systems, compared with the single particle systems. Particle processing, on the other hand, handles the mixed particle systems in concentrated suspensions. The second half of this chapter introduces the importance and characterization method of mixed particle systems in concentrated suspensions in relation to industrial processes, especially mineral processing. There has been increasing demand on the utilization of complex ores due to decrease in the accessibility of high-grade and easily extractable ores. In order to maintain the sustainable use of mineral resources, the effective beneficiation of complex ores is urgently required. It can be achieved with the selective particle dispersion/liberation and the strong assist from the mineralogical and particle characterizations.

In the eastern Pyrenees, the Axial Zone (AZ) shows a complex Alpine structure partly obscured by the Neogene tectonics, more particularly in the vallespir area. Five south-verging, in sequence thrusts are identified in the Hercynian basement.From N to S and top to bottom, there are : three major thrusts (the well established Aspres thrust, the more recently recognized Canigou and Vallespir thrusts) and two minor thrusts (Albères and Roc de France). These contacts delimit six tectonic units, an upper (Aspres), two middle (Canigou and Vallespir) and three lower (Albères, Roc de France and St-Laurent-de-Cerdans). A similar structure is reported further southwest in the Ribes de Freser area. The rhombic pattern drawn by the Alpine E-W, NW-SE and NE-SW directed thrusts in the eastern Axial Zone largely results from pre-alpine heritage (inverted late-Hercynian and Cretaceous normal faults, late-Hercynian mylonitic zones reactivated during the Alpine events). A S-dipping monocline affecting this thrust system limits the AZ and the South-Pyrenean Zone (SPZ), the AZ being raised with respect to the Alpine cover rocks of the SPZ. This monocline corresponds to the short limb of a large ramp anticline linked to the emplacement of the lowermost unit (St-Laurent-de-Cerdans). The SPZ is made up of the Cadí units overlain by allochthonous units (from W to E : Pedraforca, Coustouges, Bac Grillera, Biure and Empordà). The Cadí units (SPZ) together with theassociated middle basement units (AZ) form the Canigou nappe, a major unit below which are visible the lower basement units (AZ) in the Albères tectonic window (and in the small Freser window).The South-Pyrenean allochthons moved from N to S and their origin is likely to be found on the basement of the Canigou nappe (AZ). Except the Coustouges, lower Bac Grillera and (?) Biure small allochtons that may be rooted in the Aspres thrust (AZ), it is not possible to root the other allochtons (especially the large Pedraforca unit) in the AZ due to lack of suitable Alpine thrusts. Therefore, we are obliged to root them farther north, i.e. to the north of the North Pyrenean Fault (NPF). It is the same for the large South-Pyrenean Central Unit in the Central Pyrenees. Athough it invalidates the model commonly accepted since 25 years for the interpretation of the "ECORS-Pyrenees" seismic profile (with a large antiformal stack in the AZ), we show that this new interpretation is reasonable on two conditions: (i) an early (Lower Eocene s.l.), major, south-verging tangential tectonic regime should have existed in the central-eastern Pyrenees, which carried the European part of the chain (now the NPZ) together with the Cretaceous rift onto the South-Iberian margin (i.e. the AZ); this is clearly visible in the westernmost Pyrenees (Béarn, Aragon); (ii) this thrust system should have been modified by the late (Upper Eocene s.l.) formation and uplift of the AZ, due to the combined effects of the bordering monocline to the South and the NPF to the North. If this were the case, the present-day AZ forms a tectonic window under a system of upper units (NPZ and southern allochtons)., La Zone axiale (ZA) des Pyrénées orientales présente une structure alpine complexe en partie obscurcie par la tectonique néogène, en particulier dans le Vallespir. On identifie dans le socle hercynien cinq chevauchements à vergence S en séquence, soit du N vers le S et du haut vers le bas, trois chevauchements majeurs (chevauchement des Aspres, connu de longue date, chevauchements du Canigou et du Vallespir, plus récemment mis en évidence) et deux mineurs (chevauchements des Albères et du Roc de France). Ces contacts définissent six unités structurales, une unité supérieure (Aspres), deux unités intermédiaires (Canigou, Vallespir) et trois unités inférieures (Albères, Roc de France, St-Laurent-de-Cerdans). Une structuration analogue est visible plus au Sud-Ouest, dans la région de Ribes de Freser. Le découpage losangique dessiné par les chevauchements E-W, NW-SE et NE-SW), dans la ZA orientale, est largement la conséquence d’héritages préalpins (failles normales finihercyniennes et crétacées inversées, zones mylonitiques tardihercyniennes à rejeu alpin). Ce dispositif est affecté par une flexure bordière relevant la ZA relativement à la Zone sud-pyrénéenne (ZSP), laquelle est formée de terrains de couverture alpine. Cette flexure a valeur de mégapli de rampe frontale lié à la mise en place de l’unité inférieure la plus profonde (St-Laurent-de-Cerdans). La ZSP est constituée par les unités du Cadí sur lesquelles flottent des allochtones (Pedraforca, Coustouges, Bac Grillera, Biure, Empordà). Les unités du Cadí (ZSP) et les unités de socle intermédiaires (ZA) forment la nappe du Canigou, unité majeure sous laquelle les unités de socle inférieures (ZA) sont visibles dans la fenêtre des Albères (et la petite fenêtre du Freser). Les allochtones sont déplacés depuis le N et leur patrie est à chercher sur le socle de la nappe du Canigou (ZA). Si les klippes de Coustouges, Bac Grillera inférieure et (?) Biure peuvent être enracinées dans le chevauchement des Aspres (ZA), les autres (en particulier la grande unité de la Pedraforca) ne peuvent pas être enracinées dans la ZA, faute de chevauchement alpin adéquat, verticalisé ou non. Il est donc nécessaire de les enraciner plus au Nord, au N de la Faille nord-pyrénéenne (FNP), sous la Zone nord-pyrénéenne (ZNP) donc. Il en est de même pour la vaste Unité sud-pyrénéenne centrale des Pyrénées centrales. On montre que cette conclusion, nouvelle et qui invalide largement le modèle structural « standard » (un méga-anticlinal de nappes) habituellement admis pour la ZA depuis 25 ans pour l’interprétation du profil ECORS-Pyrénées, est possible à deux conditions : (i) qu’il ait existé dans les Pyrénées centro-orientales une tectonique tangentielle majeure précoce (Éocène inférieur s.l.) à vergence S qui a transporté le rift crétacé et la partie européenne de la chaîne (la ZNP actuelle) sur sa marge Sud ibérique (ZA), comme cela se voit très bien dans les Pyrénées plus occidentales (Béarn, Aragon) ; (ii) que ce dispositif précoce ait été altéré par la formation et le soulèvement tardifs (Éocène supérieur s.l.) de la ZA par le jeu conjoint de la flexure bordière au Sud et de la FNP au Nord ; la ZA actuelle apparaît en fenêtre sous un complexe d’unités tectoniques supérieures (ZNP, allochtones méridionaux).

International audience

3D geomodelling, a computer method for modelling and visualizing geological structures in three spatial dimensions, is a common exploration tool used in oil and gas since more than several decades. When adding time, 4D modelling allows reproducing the dynamic evolution of geological structures, and reconstructing the past deformation history of geological formations. 3D geomodelling has been applied to mineral exploration with some success since more than 15 years, but can be considered still challenging for modelling hard rock settings. If very few 4D modelling case studies have been carried out in mineral exploration, it nowadays begins to be applied in structural geology and mineral resources exploration. This paper describes the 3D and 4D geomodelling basic notions, concepts, and methodology when applied to mineral resources assessment and to modelling ore deposits. It draws on the state of the art of 3D and 4D-modelling, describing advanced techniques, limitations and recommendations. The text is illustrated by several 3D GeoModels of mineral belts across Europe, including the Fennoscandian Shield (Finland, Sweden), Hellenic (Greece), Iberian (Spain, Portugal) and Foresuedic (Poland, Germany) belts, all of those case-studies have been performed within the EU FP7 ProMine research project (Part of objectives of the 4 years ProMine project were to integrate the mapping of metal and mineral resources across the European Union, especially in WP1 and WP2). Perspectives and recommendations on applying 3 and 4 geomodelling in mineral resources appraisal are given in the conclusions.

International audience

International audience; Tungsten (VI) speciation in hydrothermal solutions is investigated through in-situ Raman spectroscopy coupled with the fused silica glass capillary technique at temperatures up to 400 °C. The effect of temperature, pH, chlorinity and carbonate speciation are evaluated. At all investigated temperatures, the tungstate ion WO4 2-(927 cm-1) is the only W species in solution at pH > 10. At a given pH, the presence of dissolved carbonates and chloride does not affect the tungsten speciation. Tungsten polymers remain stable up to 400 °C under acidic to circum-neutral pH conditions and total tungsten concentration above 0.01 mol kgH2O-1. Among the three observed polymers, namely [W7O24] 6-(paratungstate-A, ~ 960 cm-1), [W10O32] 4-(tungstate-Y, ~ 970 cm-1), and α-[H2W12O40] 6-(α-metatungstate, ~ 990 cm-1), only the hepta-and dodeca-tungstate are stable at elevated temperature. Combined with revised literature data, these results allow the thermodynamic stability constants of these W polymers to be constrained, enabling quantitative predictions of their relative abundance at temperatures up to 300 °C. These predictions suggest that W polymerization occurs under hydrothermal conditions even at low W concentration (down to 10-5 mol•kgH2O-1) under acidic conditions. These observations imply that the currently available geochemical models on W transport and deposition in deep and hot geological fluids need to be revised.

International audience; The “Marker Band” (previously called the Marker Bed and Marker Horizon [1-4]) in Gale crater is a distinctive indurated and dark-toned unit observed in the strata of Mount Sharp. From orbital data, the Marker Band (MB) was mapped across much of the western and southern edges of Mount Sharp, spanning over 80 km in distance and 1.6 km in elevation [4]. CRISM spectra of the MB show no hydration signatures and broad absorptions around~1 and 2 μm interpreted to be from high-Ca pyroxene [4]. Favored origins for the MB based upon orbital observations included a more indurated sulfate, a sandstone, and a volcanic ash deposit. The Curiosity rover recently reached the MB and is now collecting critical in situ measurements to test these postulated and other origins and make new discoveries at the finer mm- to cm-scale that could not be assessed from orbital data. Here we provide a summary of several of the most crucial MB observations made by the rover thus far from sols 3640-3645 and 3668-present.

We propose and evaluate methods for the integration of automatic implicit geological modelling into the geophysical (potential field) inversion process. The objective is to enforce structural geological realism in level-set inversion, which inverts for the location of boundaries between rock units. We propose two approaches. In the first one, a geological correction term is applied at each iteration of the inversion to reduce geological inconsistencies. This is achieved by integrating an automatic implicit geological modelling scheme within the geophysical inversion process. In the second approach, we use automatic geological modelling to derive a dynamic prior model term at each iteration of the inversion to limit departures from geologically feasible outcomes. We introduce the main theoretical aspects of the inversion algorithm and perform the proof-of-concept using two synthetic studies. The analysis of results using indicators measuring geophysical, petrophysical and structural geological misfits demonstrates that our approach effectively steers inversion towards geologically consistent models and reduces the risk of geologically unrealistic outcomes. Results suggest that geological correction may be effectively applied to pre-existing models to increase their geological realism and that it can also be used to explore geophysically equivalent models.

Le projet Relev s’appuie sur une approche interdisciplinaire en intégrant des compétences en risques naturels (géographie, génie civil, géologie), aménagement du territoire (urbanisme, architecture, génie urbain) et sciences humaines (psychologie, sociologie, histoire), pour permettre d’améliorer la gestion de la reconstruction des territoires et des populations à la suite de catastrophes naturelles.Le projet se concentre sur le relèvement en cours des îles de Saint-Martin et Saint-Barthélemy, à la suite des ouragans Irma et Maria en septembre 2017. L’approche s’est articulée autour de deux temporalités d’étude pour mieux comprendre l’évolution des stratégies de développement de ces territoires exposés aux catastrophes naturelles : d’une part, une analyse historique des stratégies d’aménagement ante-Irma (de 1947 à 2017), d’autre part un retour d’expérience interdisciplinaire post-Irma (2017-2022) pour suivre la reconstruction de ces territoires. Ce retour d’expérience s’est focalisé plus particulièrement sur :• La reconstruction physique des infrastructures endommagées (bâtiments, infrastructures et réseaux techniques),• Le redémarrage des activités du tourisme et des PME en incluant les conséquences de la crise sanitaire de la Covid-19,• Le relèvement humain du point de vue individuel et collectif (état de stress, solidarité, vie sociale, autonomie économique, habitat, etc.),• La réorganisation de la gouvernance locale.L’objectif est de s’appuyer sur une approche intégrée pour contribuer à l’émergence de nouveaux savoirs sur l’efficacité des stratégies de reconstruction post-catastrophe et de renforcer de manière cohérente la résilience des territoires face aux catastrophes naturelles,et par là même, l’adaptation au changement climatique. Les enseignements du projet Relev documentent la gestion de la phase de reconstruction post-catastrophe à Saint-Martin et Saint-Barthélemy, et soulignent la pertinence de planifier cette phase selon des modalités proches de celles déjà adoptées pour anticiper et préparer la gestion de crise. L’analyse interdisciplinaire a permis de mieux comprendre les liens de causalité entre la gouvernance de ces 2 îles, le relèvement psychosociologique des sinistrés, la reconstruction des infrastructures endommagées, la reprise des activités touristiques et l’histoire de l’urbanisation d’îles exposées aux risques naturels.En amont de futures catastrophes, les enseignements du projet alimenteront également l’élaboration d’outils et de méthodes pour anticiper la gestion de la phase de reconstruction post-catastrophe. L’approche interdisciplinaire initiée dans le projet Relev nous incite à poursuivre cet effort de rapprochement et d’échange entre les disciplines à l’avenir, notamment sur des sujets mêlant enjeux environnementaux et sociétaux.

International audience; Marl-limestone alternations are rhythmical inter-bedded deposits that commonly occur in many sedimentological environments. It is quite well established that these lithological variations originate from astronomically-driven climatic variations paced by the Milankovitch cycles of main periods 19, 23, 41, 100 and 405 ka. However, the sedimentological mechanisms involved are not clear: some models attribute these alternations to cyclic changes in the carbonate flux, while terrigenous siliciclastic input remained relatively constant. On the opposite, other models suggest that the carbonate flux was constant while the siliciclastic flux changed cyclically, or that both fluxes varied in antiphase. To test these different scenarios, we collected marlstone and limestone samples from two sedimentary marl-limestone successions from the Middle Jurassic (Bajocian, 3 marl-limestone couplets over 3.4 m) and the Lower Cretaceous (Valanginian, 1 marl-limestone couplet over 0.9 m) of the Southern French Alps (Barles). We measured their concentrations in calcium carbonate, organic carbon, nannofossil, as well as in extraterrestrial 3He (3HeET). Carbonate contents range from 45% in marls to 86% in limestones. Importantly, the measured 3HeET concentrations of all samples remained nearly constant in the siliciclastic fractions, within uncertainties (< 20%). Our results indicate that, at the astronomical timescale, sedimentation rates were mainly controlled by large changes in the CaCO3 net fluxes, leading to variable dilution of the terrigenous input. Nannofossil counting shows that pelagic CaCO3 fluxes of coccolithophores are inversely correlated to the total carbonate content along the marl-limestone alternations and represent less than 7% of the total carbonate content. Hence, in this setting, these marl-limestone alternations were driven by fluctuations in micritic CaCO3 supply and/or preservation from the nearby carbonate platform that variably diluted nannofossil and organic carbon particles. Finally, assuming a constant 3HeET flux of 100 pcc.cm-2.Ma-1, total 3HeET-derived sedimentation rates range from 20 to 30 m/Ma in the marl strata, while they reach up to 80 to 100 m/Ma in the limestone layers. These sedimentation rates are broadly compatible with local average rates estimated for the whole Bajocian and Valanginian stages by bio-cyclostratigraphy.

In many applications (e.g. object-based simulation), parametric forms are necessary to model geological bodies. In this paper, Non-uniform Rational Basis Splines (NURBS) are used to construct parametric channel forms. The models of geobodies are generated using a small number of parameters, and hence can be easily modified. This can be done by a point and click user interactions for manual editing or by a Monte-Carlo sampling onto parameter statistical distributions for stochastic simulation applications. These channel objects may also serve as support for defining facies regions in a classical reservoir 3D grid and thus for conditioning petrophysical modeling.

International audience; This paper presents a matrix formulation of factorial kriging, and its relationships with simple and ordinary kriging. Similar to other kriging methods, factorial kriging can be applied to both stationary and intrinsic stochastic processes, and is often used as a local operator. Therefore, the concepts of intrinsic random function and local stationarity are first briefly reviewed. Kriging is presented in a block matrix form in which the kriging solution is useful not only for understanding the relationships between simple and ordinary kriging methods, but also the relationships between interpolative kriging and factorial kriging. When used as a signal/noise-filtering method, factorial kriging is especially useful for multiscale modelling. Examples for general signal analysis and geophysical data signal filtering are given to illustrate the method..

International audience

International audience; The Waulsortian mudmounds consist of massive limestones that developed from late Tournaisian to early Visean. Secondary dolomitization has locally affected these mudmounds conducting to the coexistence of dolostone and limestone patches. Numerous karst cavities are preferentially developed in dolomitic intervals and are geometrically related to one or several fracture directions. These cavities, called the ``dolostone cavity type'' can be partially filled with coarse calcite and are usually bounded to the host dolostone by a calcitic transition zone which has roughly a lenticular shape. Petrographic observations, especially under cathodoluminescence, show the following sequence starting from the micro-cavities/micro-fractures network in the transition zone: 1) calcite cement in cavities, 2) dedolomite fabric, 3) host dolomite. The observed microscopic features, as well as morphological data, lead to the development of a conceptual genetic model of karst formation at macro- and microscale. In this model, first a strong dissolution of the host dolostone occurred from the fracture network thereby creating karst cavities (at macroscale) and important pervasive porosity (at microscale). Dissolution was then followed by dedolomitization in one or two-steps of the already corroded dolospar. Afterwards cementation of the residual porosity and precipitation of coarse calcite in the karst cavities occur. Even if the geological conditions under which these processes took place are not fully unraveled yet, a model that could fit with the data is presented. A discussion about the paleo-environment and paleo-hydrological conditions is settled and we also propose that the development of karst in the dolomitized mudmounds is favored by the coexistence of dolostone and limestone patches given their initial difference in porosity and competence.

The strongly incompatible behaviour of uranium in silicate magmas results in its concentration in the most felsic melts and a prevalence of granites and rhyolites as primary U sources for the formation of U deposits. Despite its incompatible behavior, U deposits resulting directly from magmatic processes are quite rare. In most deposits, U is mobilized by hydrothermal fluids or ground water well after the emplacement of the igneous rocks. Of the broad range of granite types, only a few have U contents and physico-chemical properties that permit the crystallization of accessory minerals from which uranium can be leached for the formation of U deposits. The first granites on Earth, which crystallized uraninite, dated at 3.1 Ga, are the potassic granites from the Kaapval craton (South Africa) which were also the source of the detrital uraninite for the Dominion Reef and Witwatersrand quartz pebble conglomerate deposits. Four types of granites or rhyolites can be sufficiently enriched in U to represent a significant source for the genesis of U deposits: peralkaline, high-K metaluminous calc-alkaline, L-type peraluminous and anatectic pegmatoids. L-type peraluminous plutonic rocks in which U is dominantly hosted in uraninite or in the glass of their volcanic equivalents represent the best U source. Peralkaline granites or syenites are associated with the only magmatic U-deposits formed by extreme fractional crystallization. The refractory character of the U-bearing minerals does not permit their extraction under the present economic conditions and make them unfavorable U sources for other deposit types. By contrast, felsic peralkaline volcanic rocks, in which U is dominantly hosted in the glassy matrix, represent an excellent source for many deposit types. High-K calc-alkaline plutonic rocks only represent a significant U source when the U-bearing accessory minerals (U-thorite, allanite, Nb oxides) become metamict. The volcanic rocks of the same geochemistry may be also a favorable uranium source if a large part of the U is hosted in the glassy matrix. The largest U deposit in the world, Olympic Dam in South Australia is hosted by highly fractionated high-K plutonic and volcanic rocks, but the origin of the U mineralization is still unclear. Anatectic pegmatoids containing disseminated uraninite which results from the partial melting of uranium-rich metasediments and/or metavolcanic felsic rocks, host large low grade U deposits such as the Rössing and Husab deposits in Namibia. The evaluation of the potentiality for igneous rocks to represent an efficient U source represents a critical step to consider during the early stages of exploration for most U deposit types. In particular a wider use of the magmatic inclusions to determine the parent magma chemistry and its U content is of utmost interest to evaluate the U source potential of sedimentary basins that contain felsic volcanic acidic tuffs.

SUMMARYThe numerical simulation of seismic wave propagation in realistic heterogeneous media, as sedimentary basins, is a key element of seismic hazard estimation. Many numerical methods in two dimensions are based on unstructured triangular meshes and explicit time schemes. However, the presence of thin layers and tangential stratigraphic contacts in sedimentary basins entails poorly shaped mesh elements: some triangle heights are extremely small compared to the edge lengths, which requires small time steps in the simulations and thus leads to prohibitive computation times. We compare manual and automatic geological model simplification techniques to modify problematic areas of the domain, so as to improve the quality of the triangulated mesh. We modify the shape and the connectivity between rock units in the basin, with the objective to reduce the computation time without significantly changing the physical response of the geological medium. These simplification techniques are applied in an investigation of site effects in the lower Var valley, a densely urbanized area located near the city of Nice (southeast of France). Numerical simulations of plane wave propagation in a heterogeneous 2-D profile are carried out with a discontinuous Galerkin finite element method. Five simplified meshes are generated and the impacts of the simplifications are analysed in comparison to the reference model. We compare the time solutions and the transfer functions obtained on the surface of the basin. The results show that the simplification procedures, in particular automatic modifications of the model, yield a significant performance gain, with a ratio higher than 55, while having a negligible impact on the ground motion response.

The upper Miocene Oued Belif ring-shaped breccia is located in the Nefza mining district of northern Tunisia, within the internal zone of the collisional Alpine Maghrebide belt. It encloses chaotic Triassic material (evaporites, altered siltites, and pelites) within an extrusive diapiric structure reactivated in a late Miocene nappe emplacement episode. This deep-rooted structure drove the hydrothermal activity that caused the brecciation of the Oued Belif breccia and the emplacement of two generations of shallow felsic magmatism, which, most notably, include a Serravallian granodiorite stock and a Tortonian rhyodacite dome. The inverted cone-shaped matrix-supported Oued Belif breccia comprises clasts of Triassic material and others deriving from the regional substrate, as well as a very small amount of volcanic-related material that suggests a possible phreatomagmatic origin. Fine-grained, low-Ti, Si-Al-rich hematite (≥20 vol %) is the main matrix mineral, along with rare earth element (REE) minerals (bastnaesite, parisite, and subordinate monazite) and U minerals (uraninite). The Oued Belif breccia is not an economic Cu-Au deposit, although it does possess a distinct geochemical anomaly in mafic (Cu-Co-Au) elements, with local Cu enrichment at depth (from drill core material), as well as in felsic (Bi-W-Sn-U) elements. A multiphase alteration episode (K-Fe-(Mg) metasomatism) responsible for the formation of K-feldspar, Fe phlogopite, Fe muscovite, and tourmaline, with fluorite and barite, predates the Fe-light REE (LREE)-U mineralization. The major brecciation event occurred slightly after this alteration and is coeval with the main iron oxide-LREE-U mineralization event and the emplacement of the Oued Belif rhyodacite intrusion. Hydrothermal mineralizing fluids were hot (≥540°C), saline and F-CO 2-rich brines, possibly with a mixed, basinal (salt-related) and magmatic (alkaline-related) origin. Except for its lack of economic Cu and Au content, the Oued Belif breccia shares most typical attributes of the hematite group of iron oxide copper-gold (IOCG) deposits. One may therefore classify it either as an "iron oxide-associated-alkali-altered" (Porter, 2010) or as an "iron oxide uranium" (Skirrow, 2010) mineral system. K-Ar dating of K-feldspar sets the Oued Belif breccia formation at 9.2 ± 0.25 Ma, which could make it the youngest presently known representative of the iron oxide-associated-alkali-altered-IOCG class of deposits. From a geodynamic viewpoint, the Oued Belif structure fits within a still active collisional belt, even though the Oued Belif breccia was formed in a postcollisional stage. In this respect, Oued Belif differs from most other IOCG deposits, especially from older Proterozoic ones. It nevertheless shares two essential characteristics considered necessary to yield IOCG deposits (Skirrow, 2010), namely a metasomatized subcontinental lithospheric mantle and a lithospheric delamination process. Identifying the Oued Belif breccia as a member of the iron oxide-associated-alkali-altered-IOCG family opens new frontiers within the study of IOCG deposits within the geodynamic environment of collisional belts. Future research in this area should focus particularly on the circum-Mediterranean segment of the Alpine belt. © 2013 Society of Economic Geologists, Inc.

After more than 20 years of progress, reservoir modeling still raises practical and theoretical challenges. Standard workflows are primarily built in a linear fashion (fault framework modeling, stratigraphic modeling, gridding, petrophysical modeling, upscaling, flow simulation and history matching). Modifying decisions taken at an early step of this workflow requires going through all the dependent steps and the associated quality controls once more. Whereas robustness has significantly improved and now makes it possible to improve automation and running of multiple scenarios, we identify four main limitations in the current workflows and propose possible strategies to address these limitations.First, we suggest ways to effectively sample uncertainty about well correlations by using sedimentological concepts and propagate it in existing time-to-depth conversion and gridding workflows. Then, we propose to analyze fault displacement when deciding about fault connectivity rather than discovering fault displacement in the last stage of structural framework building. Gridding should then ideally account for static data (geological structures, facies and associated permeability fields) and dynamic data (boundary conditions) while honouring discretization constraints. Although stair-step grids are a significant improvement to better handle some of these constraints, recent developments in unstructured gridding open new perspectives to address gridding challenges with more flexibility. Last, we advocate that multiple scales should be considered before the reservoir grid is created, and that connectivity and topological considerations should be used to ensure internal consistency between scales, once models have been constrained by first-order dynamic information., Après plus de 20 années de développement, la modélisation de réservoirs soulève encore des défis théoriques et pratiques. Comme les processus de géomodélisation sont organisés de manière séquentielle (modélisation du réseau de failles, de la stratigraphie, maillage, remplissage pétrophysique, mise à l’échelle, simulation d’écoulement et calage historique), toute modification à une étape donnée nécessite des mises à jour souvent fastidieuses des étapes ultérieures. De récentes améliorations de robustesse rendent possible une meilleure automatisation des tâches de géomodélisation, et permettent d’étudier plusieurs scénarios. Toutefois, nous identifions quatre pistes d’amélioration des processus de géomodélisation, et proposons des stratégies pour y remédier.Premièrement, nous suggérons d’échantillonner l’incertitude relative aux corrélations de puits à l’aide de concepts sédimentologiques, et de propager ces incertitudes aux étapes ultérieures de modélisation de réservoir. Puis, nous proposons d’analyser le champ de déplacement des failles au moment où se décide la connectivité du réseau plutôt que de considérer cette étape comme un contrôle qualité seulement à la fin de la modélisation structurale. Le maillage de réservoir doit ensuite s’accommoder de données statiques (structures, faciès et champ de perméabilité associé) et dynamiques (conditions aux limites) tout en honorant des contraintes de discrétisation. Si de récents progrès dans la création de grilles hexaédriques vont dans la bonne direction pour intégrer certaines de ces contraintes, des développements récents en génération de grilles non structurées semblent aujourd’hui prometteurs pour plus de flexibilité et d’intégration. Enfin, la problématique de l’échelle devrait trouver sa place en géomodélisation avant le maillage du réservoir. Un point fondamental est d’utiliser des critères de topologie et de connectivité pour assurer la cohérence des échelles entre elles, après avoir contraint les modèles au premier ordre avec les données dynamiques.

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The Couriège prospect (French Guiana) provides key examples of the diversity of gold distribution related to supergene processes. The nature of gold in two contrasted weathering profiles is examined as a function of the weathering lithofacies. The autochthonous profile hosts weathered Au-bearing quartz veins whereas the pediment profile is enriched in free gold issued from dismantled gold-bearing quartz veins. The gold distribution is controlled by: (1) the preservation of primary gold as free gold in both transported and autochthonous horizons and as electrum inclusions in detrital pyrite; and (2) the formation of secondary gold through dissolution/precipitation processes, expressed as gold spherulites on the free gold grain surface, an Ag-depleted rim around transported free gold grains and Ag-depleted gold micro-inclusions hosted by oxidized autochthonous pyrite. Gold enrichment through supergene chemical processes remains limited within the truncated autochthonous profile. A new conceptual model is proposed for the area, defining the role of chemical and physical processes in gold endowment and accounting for the geomorphological context. The overall evolution includes (1) deep weathering and peneplenation, (2) dismantlement and transport of lateritic material and (3) the development of a latosol cover. This study highlights that gold exploration in tropical environments must consider the residual v. transported nature and the inheritance of targeted pedogenic horizons.

Understanding mass transfer associated with fluids circulation and deformation in the Alpine orogeny is often complex due to common multistage crystallization. For example, in two emblematic and historic Pb-Ag deposits of the French Alps, Macôt-la Plagne (MP) and Peisey-Nancroix (PN), a sedimentary or orogenic origin is still debated. To discriminate between the metallogenic models of the two deposits, an integrative methodology combining field, microstructural, mineralogical, thermobarometrical, and geochronological data was here applied for establishing detailed Pressure–Temperature–Time–Deformation (P-T-t-d) mineralization conditions. Both deposits are located in Permo-Triassic quartzite of the External Briançonnais domain along the Internal Briançonnais Front (Internal Western Alps). The ore mainly occurs as veins and disseminated textures containing galena, pyrite, and variable content of tetrahedrite–tennantite and chalcopyrite. Quartz porphyroclasts and sulfide microstructures indicate a dynamic recrystallization of the quartzite during the main fluid mineralization episode. Chlorites and K-white micas (phengite) chemical analysis and thermodynamic modeling from compositional maps indicate an onset of the mineralization at 280 °C, with a main precipitation stage at 315 ± 35 °C and 6.25 ± 0.75 kbar. In situ U-Pb dating on monazite, cogenetic with sulfides, gives ages around 35 Ma for both deposits. The integrative dataset converges for a cogenetic MP-PN Alpine Pb-Ag mineralization during deformation in relation to the thrusting of the “Nappe des Gypses” and the Internal Briançonnais at the metamorphic peak.

Nickel hyperaccumulation in Blepharidium guatemalense Standl. (Rubiaceae) was found in the tropical forests of south-eastern Mexico. This study aimed to document the geographic extent of nickel hyperaccumulation in this species, to understand its process of hyperaccumulation and to explore nickel distribution within the tissues of this plant. To accomplish these objectives, a complete non-destructive elemental screening of herbarium specimens was performed with a hand-held X-ray fluorescence spectrometer. Besides, rhizosphere soils and plant tissues were collected in Mexico and analyzed for physical–chemical parameters. Finally, elemental distribution maps of nickel and other elements in plant tissues were obtained by X-ray fluorescence spectroscopy and microscopy. This study revealed that Blepharidium guatemalense is distributed throughout Chiapas, Tabasco and Campeche, reaching the maximum nickel concentration in leaves (4.3 wt%) followed by roots and seeds (2.0 wt%) and bark (1.8 wt%). Simultaneous hyperaccumulation of cobalt and nickel was found in 15% of the herbarium specimens. Blepharidium guatemalense has uncommon re-distribution mechanisms via phloem since this tissue is the highest nickel-enriched from all parts of the plant (from roots to leaves). A high total nickel (mean of 610 µg g−1) was found in rhizosphere soils even though no evidence of ophiolite emplacement in that area has been reported. Blepharidium guatemalense represents the first hypernickelophore (> 1 wt% Ni) to be reported as growing in soils that are neither ultramafic nor enriched by anthropogenic pollutants.

The relationships between the frequency shift of the ν1 stretching bands of CH4 and N2 with pressure (or density) and composition have been previously provided in the literature as reliable parameters for accurate empirical barometers and densimeters for the direct determination of the pressure or density of gas mixtures. However, the latter results still remain a pure description of the experimental data without any interpretation of the physical mechanisms hidden behind the variation trend of the observed peak position. The present paper is devoted to interpreting the origin of the pressure-induced vibrational frequency shifts of the ν1 stretching bands of CH4 and N2 within CH4–CO2, N2–CO2 and CH4–N2 binary mixtures at the molecular level. Two different theoretical models (i.e., the Lennard–Jones 6-12 potential approximation – LJ, and the generalized perturbed hard-sphere fluid – PHF) are used to intuitively and qualitatively assess the variation trend as well as the magnitude of the frequency shift of the CH4 and N2ν1 bands for an in-depth understanding. Thereby, the contribution of the attractive and repulsive solvation-mean forces to the variation of the Raman frequency shift as a function of pressure and composition is assessed. A predictive model of the variation trend of the frequency shift of the CH4ν1 band as a function of pressure (up to 3000 bars), density and composition within CH4–N2 and CH4–CO2 binary mixtures is then provided.

The SuperCam instrument, onboard the Perseverance rover (Mars 2020 mission) is designed to perform remote analysis on the Martian surface employing several spectroscopic techniques such as Laser Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman (TRR), Time-Resolved Fluorescence (TRF) and Visible and Infrared (VISIR) reflectance. In addition, SuperCam also acquires high-resolution images using a color remote micro-imager (RMI) as well as sounds with its microphone. SuperCam has three main subsystems, the Mast Unit (MU) where the laser for chemical analysis and collection optics are housed, the Body Unit (BU) where the different spectrometers are located inside the rover, and the SuperCam Calibration Target (SCCT) located on the rover's deck to facilitate calibration tests at similar ambient conditions as the analyzed samples. To perform adequate calibrations on Mars, the 22 mineral samples included in the complex SCCT assembly must have a very homogeneous distribution of major and minor elements. The analysis and verification of such homogeneity for the 5-6 replicates of the samples included in the SCCT has been the aim of this work. To verify the physic-chemical homogeneity of the calibration targets, micro Energy Dispersive X-ray Fluorescence (EDXRF) imaging was first used on the whole surface of the targets, then the relative abundances of the detected elements were computed on 20 randomly distributed areas of 100*100 mum. For those targets showing a positive Raman response, micro-Raman spectroscopy imaging was performed on the whole surface of the targets at a resolution of 100*100 mum. The %RSD values (percent of relative standard deviation of mean values) for the major elements measured with EDXRF were compared with similar values obtained by two independent LIBS set-ups at spot sizes of 300 mum in diameter. The statistical analysis showed which elements were homogeneously distributed in the 22 mineral targets of the SCCT, providing their uncertainty values for further calibration. Moreover, nine of the 22 targets showed a good Raman response and their mineral distributions were also studied. Those targets can be also used for calibration purposes of the Raman part of SuperCam using the wavenumbers of their main Raman bands proposed in this work. The authors would like to thank the Spanish Agency for Research, projects ESP2015-71965-REDT, ESP2017-87690-C3-1-R and RED2018-102600-T for funding as well as to local and regional institutions including the Basque Government, the University of the Basque Country, the Junta de Castilla y León, the University of Valladolid and the University of Malaga for their support. Support in the US was provided by NASA's Mars Exploration Program. Support in France was provided by CNES, CNRS, and local Universities. The Danish contribution was funded through support by the Carlsberg Foundation, grants CF16-0981 and CF17-0979. The team from the University of the Basque Country is very grateful to Sebastien Maussang and Victor Escobar from Renishaw for having faith in our work. The suggestions from T.R. Gabriel are gratefully acknowledged.

Scandium (Sc) is used in several modern industrial applications. Recently, significant Sc concentrations (~100 ppm) were reported in some nickel-cobalt lateritic ores, where Sc may be valuably co-produced. However, Sc is typically not included in routine analyses of Ni-Co ores. This contribution examines the relevance of using routinely analysed elements as geochemical proxies for estimating Sc concentration and distribution. Three Ni-Co lateritic deposits from New Caledonia were investigated. In each deposit, Sc is well correlated with Al2O3. The slopes of deposit-scale Sc-Al2O3 regression lines are remarkably controlled by the composition of enstatite from the parent peridotite. In all deposits, maximum Sc enrichment occurs in the yellow limonite, above the highest Ni and Co enrichment zones. Sc- and Al-bearing crystalline goethite is predominant in the oxide-rich zones, though Sc shows a higher affinity for amorphous iron oxides than Al. We propose that, in already assayed Ni-Co lateritic ores, the concentration and distribution of Sc can be estimated from that of Al. Deposit-scale Sc-Al2O3 correlations may be determined after analysing a limited number of spatially and chemically representative samples. Therefore, mining operators may get a first-order evaluation of the Sc potential resource in Ni-Co lateritic deposits at low additional costs.

International audience

The formation conditions and stability fields of Fe-serpentines are still poorly understood in both terrestrial (natural or anthropic) and extraterrestrial environments. Knowledge of the effects of physical-chemical parameters on compositional and structural features of Fe-serpentines is lacking, and only a few thermodynamic parameters of these minerals are available in the literature. To fill these gaps, the synthesis of these minerals, while controlling all the physicochemical experimental parameters, was undertaken. Two hydrothermal syntheses were carried out at 90°C to investigate the effect of two different starting mineralogical mixtures on the nature of Fe-serpentines. The run products were identified by several analytical techniques (powder X-ray diffraction, transmission, and scanning electron microscopy). Berthierine crystals were synthesized from a starting mixture of kaolinite and metal iron. The berthierines synthesized show different morphologies and iron contents (~3–38 at.%). From a starting mineralogical mixture composed of quartz and metal iron, cronstedtite crystallizes. Most of the crystals are 1M polytypes. Magnetite is always associated with both berthierine and cronstedtite. Lepidocrocite was observed only in the experiment with kaolinite. These experimental results demonstrated that Fe enrichment in serpentines depends on the silicate precursor (kaolinite or quartz) of the starting mixture. The results are also in agreement with the geochemical equilibrium predicted by thermodynamic modeling, i.e. the formation of berthierine and cronstedtite in association with magnetite at the expense of metal iron and silicates.

The Kiaka orogenic gold deposit (Burkina Faso), located in the Paleoproterozoic domain of the West African Craton, is characterized by a two-stage gold mineralization hosted in volcano-sedimentary metamorphic rocks that was formed during the Eoeburnean (2.20–2.13 Ga) and Eburnean (2.13–2.05 Ga) orogenic cycles. These two stages include an early disseminated low-grade gold mineralization and a late vein-hosted high-grade gold mineralization. Paragenetic studies indicate that the first gold stage was coeval with the deposition of hydrothermal tourmaline. The aim of this paper is twofold: (i) to determine the processes responsible for deposition of the economic disseminated gold mineralization and (ii) to identify the source of the mineralizing fluids. For this purpose, we performed an in situ study on tourmaline by combining electron probe microanalysis and secondary ion mass spectrometry measurements of boron isotopes. Hydrothermal tourmaline hosted in metamafic volcanic rocks and metagreywackes has a dravite composition but shows different δ11B values falling within the two intervals of − 25.1 to − 22.0‰ and − 19.6 to − 15.1‰, respectively. Our results suggest that tourmaline formed from a distal, high-temperature (ca. 400 °C), reduced, and low-salinity hydrothermal fluid that interacted with the local host rocks. Based on the modeling of tourmaline–fluid boron isotope fractionation, we propose a metamorphic fluid origin derived from devolatilization of deeply buried muscovite schists during the regional prograde to peak metamorphism prior ca. 2.13 Ga. This metamorphic fluid–rock interaction model may possibly extend to other orogenic gold deposits in the West African Craton.

National audience; Suite aux succès de l’outil ChemCam, le prochain rover martien Perseverance comprend un nouvel instrument franco-américain, SuperCam, qui couple la LIBS à la spectroscopie Raman ainsi qu’à la spectroscopie infrarouge passive. Grâce à la corrélation des données atomiques et moléculaires obtenues, SuperCam permettra de caractériser la chimie des sols et des roches et d’y rechercher des bio-signatures.

This paper presents the properties of fluid inclusions found in sphalerite from Latala epithermal base and precious metal deposit (Central Iran), which is hosted in Cenozoic volcanic-sedimentary host-rocks. The Latala Deposit represents an example of vein type, base metal deposits in the Miduk porphyry copper deposits (PCDs) in southern Urumieh-Dokhtar magmatic belt (UDMB). Mineralization in Latala epithermal base and precious metal vein type formed in 3 stages and sphalerite-quartz veins occur in stages 2 and 3. Stage 2 quartz-sphalerite veins are associated with chalcopyrite and zoned sphalerite, along with quartz+hematite, and Stage 3 quartz-sphalerite veins contain galena+sphalerite+ chalcopyrite and quartz with overgrowth of calcite. Mineralization in Stage 3 occurs as replacement bodies and contains Fe-poor sphalerite without zoning in the outer parts of the deposit. This paper focuses on fluid inclusions in veins bearing sphalerite and quartz. The fluid inclusion homogenization temperatures and salinity in sphalerite (some with typical zoning) range from 144 to 285 °C and from 0.2 wt.% to 7.6 wt.% NaCl eq. Sphalerite and fluid inclusions of the Latala base and precious metal deposit formed from relatively low-T and low-salinity solutions. Raman spectroscopy analyses indicate a high percentage of CO2 in the gas phase of fluid inclusions in Fe-poor sphalerites, as expected with melting temperature for CO2 of −56.6 °C, and significant amounts of H2. Lack of reduced carbon species (methane and lighter hydrocarbons) was confirmed in the petrographic study using UV light and Raman spectroscopy. High amounts of H2 in fluid inclusions of Fe-poor sphalerite can be the result of different intensities of alteration and diffusion processes. The common occurrences of CO2 in fluid inclusions have originated from magma degassing and dissolution of carbonates. The δ34S values for sulfide minerals in galena of sphalerite bearing veins vary between −9.8‰ and −1.0‰, and the δ34S values calculated for H2S are between −7.1‰ and +0.6‰. These values correspond to magmatic sulfur whit possible interaction with wall rocks. Magmatic fluids were successively diluted during cooling and continuous ascent. Secondary boiling would lead to variable amounts of potassic or prophylactic alteration and the hydrogen diffusion into the inclusions hosted in sphalerite of Latala.

International audience; Today, Laser-Induced Breakdown Spectroscopy (LIBS) imaging is in full change. Indeed, always more stable instrumentations are developed, which significantly increases the signal quality and naturally the analytical potential of the technique for the characterization of complex and heterogeneous samples at the micro-scale level. Obviously, other intrinsic features such as a limit of detection in the order of ppm, a high field of view and high acquisition rate make it one of the most complete chemical imaging techniques to date. It is thus possible in these conditions to acquire several million spectra from one single sample in just hours. Managing big data in LIBS imaging is the challenge ahead. In this paper, we put forward a new spectral analysis strategy, called embedded k-means clustering, for simultaneous detection of major and minor compounds and the generation of associated localization maps. A complex rock section with different phases and traces will be explored to demonstrate the value of this approach.

The question of frame-indifference of the thermomechanical models has to be addressed to deal correctly with the behavior of matter undergoing finite transformations. In this work, we propose to test a spacetime formalism to investigate the benefits of the covariance principle for application to covariant modeling and numerical simulations for finite transformations. Several models especially for heat conduction are proposed following this framework and next compared to existing models. This article also investigates numerical simulations using the heat equation with two different thermal dissipative models for heat conduction, without thermomechanical couplings. The numerical comparison between the spacetime thermal models derived in this work and the corresponding Newtonian thermal models, which adds the time as a discretized variable, is also performed through an example to investigate their advantages and drawbacks.

Giant hydrothermal ore deposits form where fluids carrying massive amounts of metals scavenged from source rocks or magmas encounter conditions favorable for their localized deposition. However, in most cases, the ultimate origin of metals remains highly disputed. Here, we show for the first time that two metal sources have provided, in comparable amounts, the 8 Mt of lead of the giant McArthur River zinc-lead deposit (McArthur Basin, Northern Territory, Australia). By using high-resolution secondary ion mass spectrometry (SIMS) analysis of lead isotopes in galena, we demonstrate that the two metal sources were repeatedly involved in the metal deposition in the different ore lenses ca. 1640 Ma. Modeling of lead isotope fractionation between mantle and crustal reservoirs implicates felsic rocks of the crystalline basement and the derived sedimentary rocks in the basin as the main lead sources that were leached by the ore-forming fluids. This sheds light on the crucial importance of metal tracing as a prerequisite to constrain large-scale ore-forming systems, and calls for a paradigm shift in the way hydrothermal systems form giant ore deposits: leaching of metals from several sources may be key in accounting for their huge metal tonnage.

This work aimed to develop and propose methods for evaluating the metal degree of liberation to characterize the metal deportment/concentration and liberation/association of mechanically processed waste Printed Circuit Boards (PCBs) that hold the complex and heterogeneity structure and metal distribution/association. Waste PCBs passed through a series of mechanical processing (i.e. comminution, sieving) for the metal recovery were characterized to understand and to evaluate the metal distribution and degree of liberation of the metals in order to optimize the comminution process, avoiding excessive fine particle production. The characterizations were performed at laboratory scale, as well as utilizing large scale experimental facilities, i.e. a portable X-Ray Fluorescence (XRF), micro-XRF and Synchrotron X-Ray Tomography. The proposed methods confirmed that metal liberation was very high in the fine size fraction (0.125–0.350 mm) while many locked particles were identified in the coarse size fraction (0.350–0.500 mm). Such results were analyzed and were discussed in order to better understand metal deportment/concentration behaviors. The advantages and disadvantages related to the different characterization approaches were identified and discussed in this paper, as well as their methodological developments in a waste PCBs’ mechanical processing perspective.

International audience

International audience; The reactivation of inherited tectonic structures formed during the Paleoproterozoic Trans-Hudson Orogeny (THO) has played a significant role in generating high-grade unconformity-related uranium deposits in the eastern Athabasca Basin. The role of these tectonic structures is now investigated through a series of two-dimensional hydrothermal numerical models. Two modelling scenarios are considered: (1) models during the THO peak of metamorphism and (2) models with a permeable layer mimicking the presence of the Athabasca Basin, deposited unconformably over the THO basement. In the first scenario, general fluid patterns are strongly affected by the applied permeability configurations. Unidirectional high fluid flow zones (from 10-9 to 10-8 m•s-1) and high thermal gradients (up to 65 °C•km-1) can be observed above and within the deep-seated tectonic structures. In the second scenario, well-established fluid convection cells or unidirectional fluid flow zones are observed within the basin layer, with upflow originating from the core of the deep-seated structures, regardless of the applied fluid pressure regime. These results highlight that these deep-seated structures can efficiently transport fluids and heat towards the upper parts of the crust and the basin. In the second scenario, the loci for preore alteration are then evaluated by computing a rock alteration index based on temperature and fluid velocity constraints. These alteration areas reside along and above the deep-seated structures and are potential regions for structural reactivation during mineralization. These results imply that the analysis of the inherited tectonic structures, combined with the alteration regions, can serve as markers for uranium exploration.

International audience; Phyllosilicates may trap hydrogen (H2) in the crust, but they may also produce it through various processes, including oxidative dehydrogenation. The dehydrogenation temperature depends on the type and composition of the phyllosilicates considered, but it may be as low as 300 °C. Here, we document the release of H2 and CO during thermal treatment of chloritite (300 °C) and talc (500 °C) from the Trimouns deposits (Eastern Pyrenees, France). Thermal release of gases coupled to stable isotope analysis has been used to recover and characterize H2 and CO, the two detected gases. Hydrogen content may be as high as 7 ppm with δDH2 values ranging from −258‰ to – 224‰ for sub-pure chloritite and − 140‰ for pure talc. CO content ranges between 3 ppm and 35.3 ppm with very homogeneous δ13CCO values between −27.6‰ and − 25.7‰. This study supports the idea that H2 was produced during experiments by dehydrogenation. The origin of CO remains enigmatic, but its carbon isotope composition suggests a link to the few amounts of graphite documented in chloritite and talc from the deposit. This work also reports extensive hydrogen isotope fractionation between H2 produced by dehydrogenation and both talc and chloritite. Dehydrogenation of phyllosilicates is a potential source term of H2 in numerous magmatic-hydrothermal settings and must thus be accounted for in the budget of the H2 geochemical cycle

This paper presents a new interaction point process that integrates geological knowledge for the purpose of automatic sources detection of multiple sources in groundwaters from hydrochemical data. The observations are considered as spatial data, that is a point cloud in a multi-dimensional space of hydrogeochemical parameters. The key hypothesis of this approach is to assume the unknown sources to be the realisation of a point process. The probability density describing the sources distribution is built in order to take into account the multi-dimensional character of the data and specific physical rules. These rules induce a source configuration able to explain the observations. This distribution is completed with prior knowledge regarding the model parameters distributions. The composition of the sources is estimated by the configuration maximising the joint proposed probability density. The method was first calibrated on synthetic data and then tested on real data from hydrothermal systems.

International audience; 3D geological modelling is often completed in the industry and academic research to explore sedimentary basins, target underground resources, characterise reservoirs and understand controlling processes. 3D representation of sedimentary basins integrates surface geology, well data and geophysical data until 3D consistency is obtained at the local/regional scale. Here we illustrate how 3D models of sedimentary basins contribute to exploration of resources in the context of energy transition, including water and energy resources (methane, hydrogen, geothermal), reservoir/seal pairs reconnaissance for greenhouse gas limitation and energy storage.We present recent work on the Permo-Carboniferous Lorraine-Saar-Nahe Basin that developed during from about 320 to 260 Ma during the late Variscan orogeny. This basin is buried below the Mesozoic sedimentary cover in eastern France, but extends to the northeast in Germany where the Permo-Carboniferous continental succession (up to 6 km) reaches the surface. Despite the investigations for coal exploration during the last century, there is no consistent stratigraphic and tectonic history between French and German parts of the basin. In the frame of the DEEPSURF project, we benefit from digitalised well logs and reprocessed seismic data (BRGM, ANDRA). Seismic data, initially acquired by the petroleum industries, were reprocessed with modern algorithm and interpreted to better document the geometry of this buried basin. Our interpretations integrate recent concepts in tectonics and stratigraphy to decipher the regional kinematics of this intramountain basin that developed along the Rhenohercynian orogenic suture zone.We show evidences of negative tectonic inversion from the Westphalian compression and to Stephano-Permian extension at about 305 Ma. Such geological event is marked by a major unconformity, basin wide deposition of conglomerates, subaerial exposure and erosion. These features can be responsible for the formation of a good seal for the underlying fluids in the reservoirs. Moreover, we draw new limits for the major border faults to the northwest (Metz and South Hunsrück faults) and the basin is segmented by transverse faults, thus give birth to different sub-basins with different exposure and burial history. Constraint of fault geometry is a first-order prerequisite for deep geothermal exploration. Variations of subsidence rate generate different architectures of the sedimentary infill, which control the quality of the reservoirs, and potential for energy storage. The overall 3D understanding of sedimentary basins is essential before integration of additional data such as heat distribution through time, fluid generation/migration and sediments burial history. Finally, we point out that the context of energy transition regarding subsurface exploration use the same approach as for the petroleum exploration. The access of data from former petroleum/mining investigations with the use of modern techniques and geological concepts, bring a significant reassessment for future basin resources.

International audience; This paper presents the chemical and mineralogical characterizations of a cementitious material and itsbehaviour to temperature increase in conditions close to those of radioactive waste storage. The formulation,based on a CEM III/C, silica fume, bentonite and hydrotalcite makes a low-pH cementitious grout with a lowviscosity. Results show that the mineralogical composition of this material evolves during setting. Two years aftersetting, it is a macro porous geomaterial, composed of few C-(A)-S-H with a low C/S ratio (

Mineral exploration focused on deeply concealed targets at depth requires effective techniques applicable in the field in order to identify ore-forming systems on a large scale and pathfinders to locate ore on a smaller scale. According to the rapid development of portable equipment in recent years, the importance of near real-time analysis in the field has been increasing by helping fast decision-making support before laboratory requests.Spectroscopic analysis using individual equipment has been widely used in the exploration of mineral resources, but it is rare to apply integrated data from several techniques to characterize “vectors”, which provide variations in lithology, geochemistry, mineralogy, and mineral chemistry. In addition, it is even rarer if the combination of spectral data is obtained from various portable instruments. Therefore, this study aims at reconciling geochemical data acquired from portable spectroscopic devices in order to determine the best geochemical information from each technique applied by combining the mineralogical and elemental information. Elemental and mineralogical data are provided in this study by six portable techniques: (i) elemental analyses such as XRF and LIBS for major, trace, and light elements, and (ii) mineralogical analyses such as Raman, VNIR-SWIR, MIR, and XRD to constrain rock-forming, ore, and alteration minerals. The final objective of this study is to identify vectors to the ore by applying the reconciled multi-spectral data obtained from the “real” sample in the Elvira volcanogenic massive sulfide (VMS) deposit. To achieve this, step-by-step procedures were carried out: (i) methodological understanding of each technique, (ii) establishment of a spectral database consisting of naturally monomineralic minerals, (iii) design of a decision tree to classify by mineral or mineral classes based on diagnostic bands, and mineral identification and quantification of (iv) carbonate and (v) phyllosilicate minerals (i.e., trioctahedral chlorites and dioctahedral micas), which are indicators of the target deposit.Several limitations of portable spectroscopy were confirmed based on the device itself and the geological environment in the Elvira deposit. Nevertheless, portable spectroscopy is effective in identifying the presence and compositional changes of various minerals from heterogeneous rock samples. Therefore, spectroscopic analysis on-site can be one of the vectoring tools to determine the implication for ore mineralization in hidden ore explorations., L'exploration minière axée sur des cibles cachées en profondeur nécessite (i) des techniques efficaces qui sont applicables sur le terrain pour identifier les systèmes de formation de minerai à grande échelle et (ii) des éclaireurs pour pouvoir localiser le minerai à plus petite échelle. Avec le développement rapide des équipements portables ces dernières années, l'importance de l'analyse en temps quasi réel sur le terrain a augmenté en aidant à la prise de décision rapide avant les demandes de laboratoire. Des équipements individuels ont été largement utilisés dans l'exploration des ressources minérales pour réaliser des analyses spectroscopiques. Cependant, les données obtenues par plusieurs techniques sont rarement appliquées pour caractériser les "vecteurs" qui peuvent fournir des informations intéressantes sur les variations dans la lithologie, la géochimie, la minéralogie et la chimie des minéraux. La combinaison des données spectrales obtenues à partir de divers instruments portables est encore plus rare. L’objectif principal de ce travail de thèse est de concilier les données géochimiques acquises à partir de différents appareils spectroscopiques portables afin de déterminer la meilleure information géochimique de chaque technique appliquée en combinant les informations minéralogiques et élémentaires. Dans cette étude, les données élémentaires et minéralogiques sont fournies par six techniques portables: (i) des analyses élémentaires telles que XRF et LIBS pour les éléments majeurs, les traces et les éléments légers, et (ii) des analyses minéralogiques telles que Raman, VNIR-SWIR, MIR et XRD pour contraindre les minéraux de formation de roche, de minerai et d'altération. L'objectif final de cette étude est d'identifier les vecteurs vers le minerai en appliquant les données multispectrales réconciliées, ceux qui sont obtenues à partir de l'échantillon "réel" dans le gisement de sulfure massif volcanogène (SMV) d'Elvira. Pour cela, des procédures étape par étape ont été réalisées : (i) comprendre la méthodologie de chaque technique, (ii) établir une base de données spectrales composée de minéraux naturellement monominéraux, (iii) concevoir d'un arbre de décision pour classer par minéral ou classes de minéraux en fonction des bandes diagnostiques, et identifier et quantifier des minéraux (iv) carbonate et (v) phyllosilicate (i.e., chlorites trioctaédriques et micas dioctaédriques), qui sont des indicateurs du gisement cible. Plusieurs limites de la spectroscopie portable ont été confirmées en fonction de l'appareil lui-même et de l'environnement géologique du gisement d'Elvira. Néanmoins, la spectroscopie portable est efficace pour identifier la présence et les changements de composition de divers minéraux dans des échantillons de roches hétérogènes. Par conséquent, l'analyse spectroscopique sur place peut être l'un des outils de vectorisation pour déterminer l'implication de la minéralisation dans les explorations de minerais cachés.