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International audience; The Linkam THMS 600 microthermometric stage use the fluid inclusions to deliver quantitative paleo-temperatures of subsurface past environments that are critical not only for understanding past climate evolution but also to validate the outcome of predictive models of future climates. In this case, the calibration of the microthermometric stage is the primordial condition to have the most precise temperatures. Thus the calibration of the microthermometric stage is performed from −56 to +573 °C using reversible fusions or solid-solid transitions in standards as salts, ceramics, minerals or synthetic fluid inclusions. The nine transitions measured define a linear calibration curve with negative slope, showing a correction ranging from 1.6 to 16 °C between −60 and 600 °C. The vertical and lateral gradients (temperature bias) are estimated and discussed.

International audience; Accretionary prisms constitute ideal targets to study fluid circulation and fluid-rock interactions at depths beyond the reach of active margin deep drilling. The highest-grade rocks from the Shimanto Belt on Kyushu were buried under 3-5 kbars at ~ 300°C (Toriumi and Teruya, 1988). They contain abundant quartz veins, formed throughout burial and exhumation and variably affected by brittle and ductile deformation.Cathodoluminescence (CL) reveals the existence of two distinct types of quartz, characterized by a blue and brown color, respectively. CL-blue quartz fills macro-veins (width ≥ 10μm), while CL-brown quartz is present in micro-veins (width ~ 1 − 10μm) and ductilely recrystallized domains. On the basis of microstructures, the fluids associated with the CL-blue and CL-brown quartz are interpreted as “external” and “local”, respectively. Quartz growth rims of alternating CL colors as well as mutually cross-cutting veins show that the two fluids cyclically wetted the host rock.From fluid inclusions analysis, the fluid associated with CL-blue quartz has a salinity similar to seawater, while the fluid associated with CL-brown quartz is less saline. In addition, CL-blue quartz is richer in aluminum than the CL-brown one. In contrast to the salinity/aluminum signature, the δ18O isotopic signature of both quartz types is similar and buffered by host rock. The difference between the preservation of the salinity signature of the fluid and the loss of its δ18O signature is explained by quicker exchange kinetics and larger host rock buffering capacity for isotopic reequilibration.The “local” fluid, associated with CL-brown quartz, reflects the dilution of pore water by the pure water produced by prograde dehydration reactions of clay minerals. The “external” fluid associated with CL-blue quartz is interpreted as seawater or pore water from shallow (depth

The future ExoMars rover mission (ESA/Roscosmos), to be launched in 2018, will investigate the habitability of the Martian surface and near subsurface, and search for traces of past life in the form of textural biosignatures and organic molecules. In support of this mission, a selection of relevant Mars analogue materials has been characterised and stored in the International Space Analogue Rockstore (ISAR), hosted in Orléans, France. Two ISAR samples were analysed by prototypes of the ExoMars rover instruments used for petrographic study. The objective was to determine whether a full interpretation of the rocks could be achieved on the basis of the data obtained by the ExoMars visible-IR imager and spectrometer (MicrOmega), the close-up imager (CLUPI), the drill infrared spectrometer (Ma-Miss) and the Raman spectrometer (RLS), first separately then in their entirety. In order to not influence the initial instrumental interpretation, the samples were sent to the different teams without any additional information. This first step was called the "Blind Test" phase. The data obtained by the instruments were then complemented with photography of the relevant outcrops (as would be available during the ExoMars mission) before being presented to two geologists tasked with the interpretation. The context data and photography of the outcrops and of the samples were sufficient for the geologists to identify the rocks. This initial identification was crucial for the subsequent, iterative interpretation of the spectroscopic data. The data from the different spectrometers was, thus, cross-calibrated against the photographic interpretations and against each other. In this way, important mineralogical details, such as evidence of aqueous alteration of the rocks, provided relevant information concerning potential habitable conditions. The final conclusion from this test is that, when processed together, the ExoMars payload instruments produce complementary data allowing reliable interpretation of the geological context and potential for habitable environments. This background information is fundamental for the analysis and interpretation of organics in the processed Martian rocks. © 2015 Elsevier Ltd. All rights reserved.

International audience; The present work aims at understanding the tectonic evolution of the Jebilet massif, Morocco, during the Late Paleozoic as constrained by structural, metamorphic and geochronological studies. From Late Devonian to Early Carboniferous, bordering faults controlled the opening of the Jebilet intracontinental basin (D0 stage) as shown by sedimentary infill. This episode was accompanied by a magmatic activity, newly dated between 358±7 Ma and 336±4 Ma. The first record of the Variscan event affected the Jebilet by the Late Visean‐Namurian and is represented by allochthonous superficial nappes emplaced at shallow depth in a moderately lithified sedimentary succession. D1 also developed regional‐scale recumbent folds trending E‐W that may suggest N‐S crustal shortening not generating crustal thickening, nor contributing to metamorphism. The main Variscan D2 episode consists of a progressive evolution from bulk coaxial deformation to non‐coaxial dextral transpression consistent with NW‐SE horizontal shortening, resulting in a moderate thickening. This episode was accompanied by HT‐LP metamorphism and syntectonic intrusions controlled by an inherited thermal anomaly in relation with the intracontinental rifting stage (D0). Based on previous age determinations from syntectonic leucogranite and metamorphic rocks, D2 is dated between 310 and 280 Ma. The tectono‐metamorphic evolution of the Jebilet massif can be correlated with a plate‐tectonic scenario evolving from, first a Late Devonian–Early Carboniferous basin formation during stretching of the north‐Gondwana margin and initiation of the Paleotethys Ocean, and, second, to a Late Carboniferous‐Early Permian ocean closure (Rheic or Paleotethys Oceans depending of scenarios) that resulted in the final Variscan‐Alleghanian tectonics.

International audience; Fossil structures, such as exhumed accretionary prisms, are the only direct recorders of the fluids wetting the plate interface near the base of the seismo­ genic zone. By studying exhumed accretionary prisms, it is thus possible to determine the physicochemical properties of fluids and the geometry and dynamics of their circulation. We considered here two transects encompass­ ing the brittle­plastic transition (BPT) zone, in the Franco­Italian Alps and the Shimanto Belt in Japan, and compared our data with a broader set of exam­ ples from the literature. On quartz that grew synkinematically at peak burial conditions, we inferred fluid properties indirectly from quartz trace­element concentrations (using cathodoluminescence [CL] imaging) and directly from fluid­inclusion composition and P­ρ­T properties (using Raman and micro­ thermometry). At ~250 °C, quartz grew principally through fracturing and two types of quartz, a CL­brown and a CL­blue, precipitated alternately. At ~350 °C, where plastic deformation and recrystallization is pervasive, only a single, ho­ mogeneously CL­brown quartz is present. The salinity of the fluid in the inclu­ sions shallower than the BPT is consistently of the order or lower than sea­ water, while salinities are very scattered deeper than the BPT and often exceed seawater salinity. The gas dissolved in the fluid is predominantly CH 4 shal­ lower than the BPT, and either CH 4 or CO 2 deeper than the BPT, depending on the nature of the host rock and in particular on the proportion of carbonates. Cathodoluminescence properties, salinity, and nature of the gas all point to a closed­system behavior in rocks deeper than the BPT. In contrast, shallower than the BPT (i.e., at seismogenic depths), textures revealed by CL­imaging evidence the episodic influx of an external fluid, leading to the crystallization of CL­blue quartz. The scale of the circulation leading to the generation of the CL­blue quartz, or its relationship with the seismic cycle, is still unclear. Be­ sides, the fluid pressure recorded in the abundant water­rich fluid inclusions is systematically much lower than the corresponding lithostatic pressure, ir­ respective of the depth domain considered. For inclusions trapped at large depth, the low fluid pressure recorded in the inclusions reflects post­entrap­ ment reequilibration. For inclusions trapped at shallower conditions, typically at seismogenic depths, the low fluid pressure may as well be the result of large fluid pressure drop after earthquakes.

International audience; The pressure of deep fluids in subduction zones is a major control on plate boundary strength and earthquake genesis. The record, by methane-rich fluid inclusions, of large (~ 50–100 MPa) and instantaneous pressure variations in the Shimanto Belt (Japan) points to the presence of large fluid overpressure at depth (300–500 MPa, ~ 250 °C). To further analyze the connection between methane and fluid overpressure, we determined with Rock-Eval the potential for a worldwide selection of deep seafloor sediments to produce methane as a result of organic matter (OM) cracking due to temperature increase during subduction. The principal factor controlling the methanogenesis potential of sediments is OM proportion, while OM nature is only a subordinate factor. In turn, OM proportion is mainly controlled by the organic terrigenous input. Considering a typical sediment from ocean-continent subduction zones, containing 0.5 wt% of type III OM, cracking of OM has two major consequences: (1) Methane is produced in sufficient concentration as to oversaturate the pore-filling water. The deep fluid in accretionary prisms is therefore a mechanical mixture of water-rich and methane-rich phases; (2) CH4 production can generate large fluid overpressure, of the order of several tens of MPa, The conditions for these large overpressure are a low permeability of the upper plate (< 2.10− 21 m2) and décollement zone (< 10− 18 m2), which may be prevailing in the depth domain (z > 10 km) where OM thermal cracking occurs. At these depths, OM thermal cracking appears as a source of overpressure larger than the last increments of smectite-to-illite reaction. Such large overpressures play potentially a role in facilitating slip along the plate interface. Conversely, the scarcity of earthquakes in ocean-ocean subduction zones such as Marianna or Barbados may be related to the low influx of detrital OM and the limited methane/overpressure generation at depth.

The analytical technique PIXE experiment for measuring light and heavy elements concentration inside different samples of soil and residual water collected in the region of Safi-El Jadida, where an industrial complex resided, was performed. The same method was used to investigate the presence of elements ranging from silicon to lead in different soils samples and seaweed collected upstream from the site of Safi-El Jadida industrial zone, inside lands and downstream of it, in the entrance of the Casablanca region. This study allows us to highlight the influence of activities of this industrial zone on the neighbouring areas the site.

Analyses by the Mars Exploration Rover (MER), Spirit, of Martian basalts from Gusev crater show that they are chemically very different from terrestrial basalts, being characterized in particular by high Mg- and Fe-contents. To provide suitable analog basalts for the International Space Analogue Rockstore (ISAR), a collection of analog rocks and minerals for preparing in situ space missions, especially, the upcoming Mars mission MSL- 2011 and the future international Mars-2018 mission, it is necessary to synthesize Martian basalts. The aim of this study was therefore to synthesize Martian basalt analogs to the Gusev crater basalts, based on the geochemical data from the MER rover Spirit. We present the results of two experiments, one producing a quench-cooled basalt (

International audience; In this work PIXE experiments were performed for measuring heavy and light elements (ranging from aluminium to lead) concentrations inside various polluted and unpolluted soils as well as liquid samples collected from different phosphate factory sewers in the El Jadida-Safi Atlantic coastal region (Morocco). In addition, uranium (238U) and thorium (232Th) contents were evaluated in the same samples studied by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). The influence of the phosphate industry wastes on the concentrations of both radioactive and non-radioactive elements of the samples studied was investigated.

Siliceous hot-spring deposits, or sinters, typically form in active, terrestrial (on land), volcanic terrains where magmatically heated waters circulating through the shallow crust emerge at the Earth's surface as silica-charged geothermal fluids. Geyserites are sinters affiliated with the highest temperature (~ 75–100 °C), natural geothermal fluid emissions, comprising localized, lithologically distinctive, hydrothermal silica precipitates that develop around geysers, spouters and spring-vents. They demarcate the position of hot-fluid upflow zones useful for geothermal energy and epithermal mineral prospecting. Near-vent areas also are “extreme environment” settings for the growth of microbial biofilms at near-boiling temperatures. Microbial biosignatures (e.g., characteristic silicified microbial textures, carbon isotopes, genetic material, lipid biomarkers) may be extracted from modern geyserite. However, because of strong taphonomic filtering and subsequent diagenesis, fossils in geyserite are very rare in the pre-Quaternary sinter record which, in and of itself, is patchy in time and space back to about 400 Ma. Only a few old examples are known, such as geyserite reported from the Devonian Drummond Basin (Australia), Devonian Rhynie cherts (Scotland), and a new example described herein from the spectacularly well-preserved, Late Jurassic (150 Ma), Yellowstone-style geothermal landscapes of Patagonia, Argentina. There, geyserite is associated with fossil vent-mounds and silicified hydrothermal breccias of the Claudia sinter, which is geologically related to the world-class Cerro Vanguardia gold/silver deposit of the Deseado Massif, a part of the Chon Aike siliceous large igneous province. Tubular, filament-like micro-inclusions from Claudia were studied using integrated petrographic and laser micro-Raman analysis, the results of which suggest a biological origin. The putative fossils are enclosed within nodular geyserite, a texture typical of subaerial near-vent conditions. Overall, this worldwide review of geyserite confirms its significance as a mineralizing geological archive reflecting the nature of Earth's highest temperature, habitable terrestrial sedimentary environment. Hot-spring depositional settings also may serve as analogs for early Earth paleoenvironments because of their elevated temperature of formation, rapid mineralization by silica, and morphologically comparable carbonaceous material sourced from prokaryotes adapted to life at high temperatures. Fil: Campbell, Kathleen A.. The University Of Auckland; Nueva Zelanda. Centre National de la Recherche Scientifique; Francia Fil: Guido, Diego Martin. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gautret, Pascale. Centre National de la Recherche Scientifique; Francia. Université d; Francia. Institut des Sciences de la Terre d; Francia Fil: Foucher, Frédéric. Centre National de la Recherche Scientifique; Francia Fil: Ramboz, Claire. Centre National de la Recherche Scientifique; Francia. Université d; Francia. Institut des Sciences de la Terre d; Francia Fil: Westall, Frances. Centre National de la Recherche Scientifique; Francia

International audience; In the Upper Rhine Graben, geothermal projects are strongly under development, particularly for the exploitation of fluid in the deeper part of the basin.This type of reservoirs constitutes a fractured dominated system. However, the hydraulic behaviour of the fracture network is poorly known and its knowledge constitutes an important way to better target the exploration works. Combining data from structural analysis, mineralogical analysis of fracture filling from outcrops and drilling cores and fluid geochemical analysis from deep boreholes, we propose a new model of fluid circulation in the deeper part of the Rhine Graben.The present-day fluids collected from the basement and the Buntsanstein sandstones in the deepest wells have the same originand are totally different to those from Tertiary sediments. These deep fluidshave reacted with deep sedimentary rocks at about 4 or 5 km depth before migrate through the graben and probably diluted at small proportions with meteoritic freshwaters.These fluids circulate through a fracture network constitutes by different sets linked to the tectonic history of the Rhine Graben. In the basement, the Hercynian fractures, oriented NE-SW and NW-SE, show two successive stages of fillingsshowing two fluid circulation pulses: 1) asheared/cataclased phase associated with illite and quartz, which is prior to the graben opening;2) precipitation of dolomite in tension fractureslinked to theearly stage of the graben formation.An other main direction fracture set is present in the basement, probably reactivated, and in the Permo-Triassic sandstones with a N-S direction. On outcrops, this fracture set have no macroscopic mineralogical fillings, but in boreholes and for some large shear zone in the sandstones, a cataclasis phase associated to quartz and illite, and radial illite in tension fracture in the granite, and barite in the Buntsandstein sanstonesis present.This study suggests that the reactivation of old Hercynian structures, oriented NE-SW and NW-SE, in relation with the Tertiary tectonic history of the graben formation develops the fluid/basement interaction in deep temperature conditions. In the contrary, the N-S large structures favor recent circulation system and rather constitute a recharge drain

The Radka deposit is one of the largest Cu–Au epithermal deposits related to Late Cretaceous volcanic arc-type magmatic activity in the Panagyurishte ore region, central part of the Srednogorie zone, Bulgaria. The mineralogical and geochemical features of a vinciennite-bearing Cu–As–Sn (± Au) assemblage at Radka show very similar characteristics to those in other vinciennite-bearing high-sulfidation epithermal deposits worldwide. The assemblage consists of enargite, Cu-excess tennantite, chalcopyrite, gold, vinciennite, colusite, and minor covellite, within a gangue of barite, illite, and quartz. A detailed electronmicroprobe study of vinciennite and associated minerals reveals the heterovalency of Cu and Fe. New data on the composition of vinciennite sheds light on aspects of its crystal chemistry, such as incorporation of Cu 2+ and Fe 3+ and Sn 4+ Ge 4+ substitution, and leads us to propose a new empirical formula: Cu + 8Cu 2+ 2Fe 3+ 3(Fe,Cu) 2+ (Sn,Ge) 4+ (As,Sb) 5+ S16 2– . Infrared microthermometry of enargite-hosted fluid inclusions provides constraints on the conditions of deposition of this unusual assemblage in the context of the evolution of the magma-related ore-forming system at Radka. The assemblage was formed by oxidized and slightly acid fluids, with a dominantly magmatic signature, high fugacity of sulfur and intermediate salinity (about 10 wt.% eq. NaCl) at a temperature of about 275°C. In view of the geology of the Radka deposit, its mineralogical and geochemical peculiarities, ore textures, type of hydrothermal alteration and the character of the fluids, we interpret the deposit as a deep part of a high-sulfidation epithermal mineralization, possibly genetically related to a porphyry copper system.

International audience; The Neoproterozoic to Cambrian formations that compose the cover of the Bou Azzer–El Graara inlier, host a great number of Copper occurrence whose origin is largely discussed. To bring some light to this debate, structural, petrographic and geochemical observations were performed on the copper deposit of Jbel Laassel. This deposit, located at the extreme ESE of the Bou Azzer–El Graara inlier, is mined since 2012. At the district scale, the ore bodies localize in a folding band that extends along a NE–SW direction. At macroscopic, microscopic and scanning electron microscope scales the mineralization appears as banding veins, with locally cockade breccia and comb quartz textures. From the macroscopic scale to the scale of the scanning electron microscope, all these mineralized textures are connected there between forming a stockwork with an auto-similar structure in the range of used scales of observation. At the district scale, this stockwork is preferentially located in the anticlinal hinges of the folding band. Principal component analyses of geochemical database enable to distinguish several groups of chemical elements, each of these groups corresponding to the different lithologies and to the copper mineralization. This last group does not show any correlation with the distinguished lithological groups. All these observations bring new arguments to an epigenetic origin for the copper mineralization of the Jbel Laassel deposit, with a formation contemporary or posterior with the folding band development attributed to Variscan deformation.

Pyrite samples from the Radka epithermal, replacement type, volcanic rock-hosted copper deposit, Bulgaria, have been studied using near-infrared (IR) microscopy. Two generations of pyrite based on their textures, composition and behaviour in IR light can be distinguished. Electron microprobe analyses, X-ray elemental mapping and Fourier transform infrared spectroscopy were used to study the relationship between crystal zoning, trace element contents and IR transmittance of pyrite. The observed crystal zoning is related to variable arsenic contents in massive fine-grained and colloform pyrite from the early pyrite–quartz assemblage, and cobalt contents in pyrite crystals from the late quartz–pyrite vein assemblage. There is a negative correlation between trace element content and IR transmittance of pyrite. The IR transparency of pyrite is thus a sensitive indicator of changes in trace element concentrations. Fluid inclusions have only been found in the second pyrite generation. Scanning electron microscopy observations on open fluid inclusion cavities permitted the crystallographic features of vacuoles to be determined. A characteristic feature of primary fluid inclusions in pyrite is a negative crystal habit, shaped mainly by {100}, {111} and {210}. This complicated polyhedral morphology is the reason for the observed opacity of some isometric primary inclusions. Secondary fluid inclusion morphology depends on the nature of the surface of the healed fracture. Recognition of the primary or secondary origin of fluid inclusions is enhanced by using crystallographically oriented sections. Microthermometric measurements of primary inclusions indicate that the second pyrite generation was deposited at maximum P–T conditions of 400 °C and 430 bar and from a fluid of low bulk salinity (3.5–4.6 wt%), possibly KCl-dominant. There are large ranges for homogenisation temperatures in secondary inclusions because of necking-down processes. Decrepitation features of some of pyrite-hosted inclusions and of all inclusions in associated quartz indicate reheating of the veins to 500–550 °C. The late cobalt-rich quartz–pyrite vein assemblage in the Radka deposit may be the shallow manifestation of deeper and genetically related porphyry copper mineralisation. This is a common observation of many intermediate- to high-sulfidation epithermal replacement-type ore bodies in this ore district and possibly the Cretaceous Banat–Srednogorie metallogenic belt in general.

Light and heavy trace elements can be analysed simultaneously by particle-induced X-ray emission (PIXE) using an Al-funny filter (a filter with a hole drilled at its centre, placed in front of the detector window). The treatment of spectra, performed using the GUPIX code, requires the determination of an instrumental constant H . In theory and when using ordinary filters, H is a constant corresponding to the detection solid angle. In contrast, we have observed that H varies with X-ray energy using a funny filter. This is due to an inaccurate description of the geometry of the detection: detector-to-target distance, filter thicknesses and hole diameter of the funny filter. We develop a methodology to determine the effective values of the four geometrical parameters from a calibration of H using standards. In turn, H recalculated using these effective values is a constant equivalent to the effective detection solid angle.

The present study is focused on the so-called High Temprature Reaction Zone of the Oman ophiolite, a thin zone located between the roots of the sheeted dyke complex and the high-level gabbros marking the roof of the fossil magma chambers. The distribution of diabases, chloritised dykes, spilitized dykes and epidosites (in the order of increasing hydrothermal alteration) was studied along continuous outcrops of the lower sheeted dyke complex in three selected areas. The Muwaylah section, in the Haylayn massif, representing a fossil axial discontinuity, is the most massively epidotised area, with epidosite zones of 3–15 m wide and an average spacing of 12 m. In this area, there are two directions of dyking, and a massive sulfide deposit (Daris prospect). The wadi Andam area (Samail massif), representing a much less tectonised site, close to a mantle diapir and located probably midway between the tip and the center of an accretion segment, is also well epidotised, with epidosites spacing of 10–25 m. The wadi Salahi area probably represents the central part of a fossil accretion segment and is by far the least altered site, in spite of being located quite beneath the Zuha sulfide prospect. This confirms that the hot ascending fluids in major discharge zones are strongly focused. Fluid inclusions from about 50 samples collected in the plagiogranites, gabbros and sheeted dykes of the Muwaylah and wadi Falah areas (SE Haylayn massif), consist of: (1) monophase (liquid) inclusions, generally stretched and deformed; (2) vapour-dominated, low-salinity, 2-phase inclusions, with average salinity of 3.8 wt% eq. NaCl and an average Th of 370thinsp°C; (3) liquid-dominated, low-salinity, 2-phase inclusions, with an average salinity of 4.2 wt% eq. NaCl and an average Th of 325thinsp°C, and (4) liquid-dominated, high-salinity inclusions, containing a solid halite daughter phase, dissolving at higher temperature (292–441thinsp°C ) than homogenisation of the fluid phases (230–403thinsp°C ). One plagiogranite sample collected in the Muwaylah area (Haylayn massif) is particularly rich in quartz-epidote hydrothermal veins. Xenomorphic globular quartz is rich in high-salinity, brine-rich inclusions, with halite cubes dissolving at very high temperatures (358–496thinsp°C ) yielding very high salinities (43 to 59.2% NaCl eq.), and with liquid-vapour homogenisation of 275thinsp°C on average. Molecular Raman Spectroscopy analyses have confirmed the aqueous nature of these inclusions and the absence of detectable CO2, NH4, N2 and SO2. Daughter solid phases other than NaCl were determined as hematite and anhydrite, and a third phase is hydroxyl-bearing (amphibole?). PIXE analyses on six brine-rich inclusions allowed to detect significant but variable contents in Cl, Fe, Mn, K, Ca, Zn and Br. Copper, remarkably, was never detected, and two measured Cl/Br ratios are close to that of seawater. The measurement of oxygen isotopic ratios of the fluids extracted from some fluid inclusions and of associated host-minerals (quartz, epidote) suggest that both seawater-derived and magma-derived fluids have mixed in the High Temperature Reaction Zone. PIXE data yield a similar conclusion, based on the contrasted Fe and Mn-contents and Cl/Br ratios of the analysed inclusions. However, the oxidised and Cu-depleted nature of the brine-rich inclusions suggests that the magma-derived or seawater-derived brines are residual liquids that have degassed. Present V-X properties of most NaCl-saturated inclusions do not keep the record of the boiling process, as they homogenise by halite disappearance and not by vapour disappearance. Probably they have been modified by several post-trapping changes, for instance by necking.

International audience; In paleo-accretionary prisms and the shallow metamorphic domains of orogens, circulating fluids trapped in inclusions are commonly composed of a mixture of salt water and methane, producing two types of fluid inclusions: methane-bearing aqueous and methane-rich gaseous fluid inclusions. In such geological settings, where multiple stages of deformation, veining and fluid influx are prevalent, textural relationships between aqueous and gaseous inclusions are often ambiguous, preventing the microthermometric determination of fluid trapping pressure and temperature conditions. To assess the P-T conditions of deep circulating fluids from the Hyuga unit of the Shimanto paleo-accretionary prism on Kyushu, Japan, we have developed a new computational code, applicable to the H2O-CH4-NaCl system, which allows the characterization of CH4-bearing aqueous inclusions using only the temperatures of their phase transitions estimated by microthermometry: Tmi, the melting temperature of ice; Thyd, the melting temperature of gas hydrate and Th,aq, homogenization temperature. This thermodynamic modeling calculates the bulk density and composition of aqueous inclusions, as well as their P-T isochoric paths in a P-T diagram with an estimated precision of approximatively 10 %. We use this computational tool to reconstruct the entrapment P-T conditions of aqueous inclusions in the Hyuga unit, and we show that these aqueous inclusions cannot be cogenetic with methane gaseous inclusions present in the same rocks. As a result, we propose that pulses of a high-pressure, methane-rich fluid transiently percolated through a rock wetted by a lower-pressure aqueous fluid. By coupling microthermometric results with petrological data, we infer that the exhumation of the Hyuga unit from the peak metamorphic conditions was nearly isothermal and ended up under a very hot geothermal gradient. In subduction or collision zones, modeling aqueous fluid inclusions in the ternary H2O-CH4-NaCl system and not simply in the binary H2O-NaCl is necessary, as the addition of even a small amount of methane to the water raises significantly the isochores to higher pressures. Our new code provides therefore the possibility to estimate precisely the pressure conditions of fluids circulating at depth.

Geological fluids contain water, chlorides and Na as major components, and metals, CO2 gas and CH4 gas as minor or major components. Quantitative analysis of geological fluids in fluid inclusions and hydrothermal minerals is vital to the characterization of fluid-rock interactions. The presence and quantity of trace and minor elements can be determined in fluid inclusions and minerals by Proton-induced-X-ray-emission (PIXE) and Proton-induced-gamma-ray-emission (PIGE) with EDS analysis, based on computer-aided interpretation of X-ray spectra. A feature of the PIXE-PIGE method is the long range (deep penetration) of protons in light matrices, which allows near-surface inclusions to be analysed. The applications presented here concern samples from submarine hydrothermal deposits (Red Sea, Lau Basin), and from skarns in Central Morocco. In submarine hydrothermal processes, PIXE data show trace-element-bearing-mineral(s) in assemblages with bulk geochemical anomalies, e.g. Co- and Pb-contents in the 1000 ppm range in chalcopyrite from the Hine-Hina field, Lau basin. PIXE data for high T chimneys of the Atlantis II deep record trace element perturbations due to boiling. Hypersaline magmatic fluids in the Sn-skarns of El Hammam contain more than 1000 ppm Cu and Pb but no Zn. A Sn-borate, nordenskioldine, has been identified in the high T-skarns, trapping a Li-bearing concentrated brine.

International audience; In the Upper Rhine Graben, geothermal projects are strongly under development, particularly for the exploitation of fluid within the top of the basement. This type of reservoirs constitutes a fractured dominated system. However, the hydraulic behaviour of the fracture network is poorly known, such as connexion, main fluid flow direction, role of the fault zone versus minor fractures, the deformation types (cataclase, fault, crack...). We propose two approaches to understand the fluid flow for a better geothermal exploitation in the Upper Rhine Graben. The first approach is to study the fillings of the fracture which plug partially or totally the current fluid flow. The second approach is to determine the nature of the palæo-circulations by studying fracture fillings, their textures and establish mineral sequence of fillings in relation to the tectonic phases and the geological history of the basement. And finally we compare chemistry of palæo-fluids with those of present-day fluids which flow in the deeper part of the Upper Rhine Graben. In this work, we propose a combined structural and mineralogical analysis of the fractures and their fillings based on samples collected on the EPS1 Soultz cores and outcrops on the both flanks of the Upper Rhine Graben. These mineralogical fillings have been sampled within fractures identified by measuring their orientation and defining their relative age. Petrological study (Optical microscope, Scanning Electron Microscope noted SEM, cathodoluminescence noted CL) completed by chemical analyses (Electron Microprobe Analyses, noted EPMA) have been performed in order to determine the filling minerals and their relationships. Among filling minerals, quartz, carbonates and illite are the major ones. Different types and generations of carbonates (calcite, dolomite, ankerite, Mn-bearing carbonates and siderite) have been highlighted at the scale of the major fracture zones in the upper part of granite, using CL and EPMA. Combined mineralogical, textural and structural data allow establishing a chronology of the palæo-circulations relative to the tectonic phases and the geological history of the basement. We identify the major phases which plug the fractures and, consequently, the set of fractures which remain more permeable to the current fluid flow.

International audience; Liquid water at atmospheric pressure can be supercooled to 41 C (ref. 1) and superheated to C302 C (ref. 2). Experiments involving fluid inclusions of water in quartz suggest that water is capable of sustaining pressures as low as 140 MPa before it breaks by cavitation3. Other techniques, for which cavitation occurs consistently at around 30MPa (ref. 4), produce results that cast doubt on this claim. Here we reproduce the fluid-inclusion experiment, performing repeated measurements on a single sample--a method used in meteorology5, bioprotection6 and protein crystallization7, but not yet in liquid water under large mechanical tension. The resulting cavitation statistics are characteristic of a thermally activated process, and both the free energy and the volume of the critical bubble are well described by classical nucleation theory when the surface tension is reduced by less than 10%, consistent with homogeneous cavitation. The line of density maxima of water at negative pressure is found to reach 922:8 kgm3 at around 300 K, which further constrains its contested phase diagram.

International audience; Instruments for surface missions to extraterrestrial bodies should be cross-calibrated using a common suite of relevant materials. Such work is necessary to improve instrument performance and aids in the interpretation of in-situ measurements. At the CNRS campus in Orléans, the Observatoire des Sciences de l'Univers en région Centre (OSUC) has created a collection of well-characterised rocks and minerals for testing and calibrating instruments to be flown in space missions. The characteristics of the analogue materials are documented in an accompanying online database. In view of the recent and upcoming rover missions to Mars (NASA's 2011 Mars Science Laboratory (MSL) and ESA/Roscosmos' 2018 ExoMars), we are concentrating initially on materials of direct relevance to the red planet. The initial collection consists of 15 well-studied rock and mineral samples, including a variety of basalts (ultramafic, weathered, silicified, primitive), sediments (volcanic sands, chert, and a banded iron formation -BIF-), and the phyllosilicate nontronite (a clay). All the samples were characterised petrographically, petrologically, and geochemically using the types of analyses likely to be performed during in-situ missions, in particular ExoMars: hand specimen description; optical microscopy; mineralogical analysis by XRD, Raman and IR spectrometry; iron phase analysis by Mössbauer spectroscopy (MBS), elemental analysis by Energy-Dispersive X-ray spectroscopy (EDX), microprobe, Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) and Mass Spectrometry (ICP-MS); and reduced carbon analysis by Raman spectrometry.

International audience; Water is famous for its anomalies, most of which become dramatic in the supercooled region, where the liquid is metastable with respect to the solid. Another metastable region has been hitherto less studied: the region where the pressure is negative. Here we review the work on the liquid in the stretched state. Characterization of the properties of the metastable liquid before it breaks by nucleation of a vapour bubble (cavitation) is a challenging task. The recent measurement of the equation of state of the liquid at room temperature down to 26 MPa opens the way to more detailed information on water at low density. The threshold for cavitation in stretched water has also been studied by several methods. A puzzling discrepancy between experiments and theory remains unexplained. To evaluate how specific this behaviour is to water, we discuss the cavitation data on other liquids. We conclude with a description of the ongoing work in our groups.

International audience; High helium contents will be generated within minor actinide doped uranium dioxide blankets which could be used in fourth generation reactors. In this framework, it is essential to improve our understanding of the type of damage which a pellet could incur as a result of extensive helium build-up. This paper is an attempt at tackling this issue. Sintered uranium dioxide disks have been implanted with helium ions then annealed at various temperatures. Above a concentration of 0.4 at.% and above 1000°C, optical images of the sample surface revealed swollen grains and extensive areas which have exfoliated. Nuclear reaction microanalyses and atomic force microscopy observations were performed to demonstrate that helium has substantially precipitated within the swollen grains. Massive precipitation of the gas leads under these conditions to sample surface blistering which appears to precede flaking. Deuterium ion irradiations have also been performed at ambient and a direct flaking of the sample surface was observed, but for this phenomenon to be observed required much higher doses than in the He study, indicating that temperature could be an essential ingredient for gas to migrate and cause extensive precipitation. Such phenomena could possibly lead to degradation of the fuel.

International audience; The Jabali deposit (3.8 Mt at 16% Zn, 2% Pb and 132 g/t Ag) is hosted by dolomitized platform carbonates of Kimmeridgian age at the southwestern edge of the oil-producing Wadi al Jawf rift basin in northern Yemen. Paleogeographical reconstructions demonstrate that tensional synsedimentary tectonic activity from the Late Jurassic to Early Cretaceous was responsible for the thick accumulation of argillaceous and evaporitic sediments in the subsident rift basin, the unstable margin of which was the site of rapid facies changes, local disconformities and periods of emergence, as well as of dolomitization along the WNW- and NNW-striking boundary fault system. In the Jabali area, the upper part of the Jurassic sequence underwent two stages of dolomitization before emergence and deep karstic erosion. Solution cavities and depressions in the eroded surface were filled by dolomite sand and black pyritic mudstone prior to a last marine transgression of limited extent. Subsequent ore deposition and associated late dolomitization sealed the network of solution cavities, impregnating the dolomite sands and the host dolomites. Sphalerite I and wurtzite, followed by silver-bearing zoned sphalerite II associated with galena, crystallized from a cyclic influx of low-temperature (75-100°C) saline solutions. Lead isotope geochemistry indicates that the lead, zinc and silver probably originated from an Early Proterozoic basement. The dissolved metals were likely derived from the basal aquifer (detrital material of basement origin) of the evaporite-bearing sequence filling the Wadi al Jawf trough. Migrating metalliferous brines from the basin to the uplifted Jabali area, where ore deposition was favoured by a reducing environment, were probably channelled by the boundary fault system during the last stages of synsedimentary tectonic activity.

International audience; The Callovian-Oxfordian (COx) clayey unit is being studied in the Eastern part of the Paris Basin at depths between 400 and 500 m depth to assess of its suitability for nuclear waste disposal. The present study combines new mineralogical and isotopic data to describe the sedimentary history of the COx unit. Petrologic study provided evidence of the following diagenetic mineral sequence: (1) framboidal pyrite and micritic calcite, (2) iron-rich euhedral carbonates (ankerite, sideroplesite) and glauconite (3) limpid calcite and dolomite and celestite infilling residual porosity in bioclasts and cracks, (4) chalcedony, (5) quartz/calcite. Pyrite in bioturbations shows a wide range of δ34S (−38‰ to +34.5‰), providing evidence of bacterial sulphate reduction processes in changing sedimentation conditions. The most negative values (−38‰ to −22‰), measured in the lower part of the COx unit indicate precipitation of pyrite in a marine environment with a continuous sulphate supply. The most positive pyrite δ34S values (−14‰ up to +34.5‰) in the upper part of the COx unit indicate pyrite precipitation in a closed system. Celestite δ34S values reflect the last evolutionary stage of the system when bacterial activity ended; however its deposition cannot be possible without sulphate supply due to carbonate bioclast dissolution. The 87Sr/86Sr ratio of celestite (0.706872-0.707040) is consistent with deposition from Jurassic marine-derived waters. Carbon and oxygen isotopic compositions of bulk calcite and dolomite are consistent with marine carbonates. Siderite, only present in the maximum clay zone, has chemical composition and δ18O consistent with a marine environment. Its δ13C is however lower than those of marine carbonates, suggesting a contribution of 13C-depleted carbon from degradation of organic matter. δ18O values of diagenetic chalcedony range between +27‰ and +31‰, suggesting precipitation from marine-derived pore waters. Late calcite crosscutting a vein filled with chalcedony and celestite, and late euhedral quartz in a limestone from the top of the formation have lower δ18O values (not, vert, similar+19‰), suggesting that they precipitated from meteoric fluids, isotopically close to present-day pore waters of the formation. Finally, the study illustrates the transition from very active, biotic diagenesis to abiotic diagenesis. This transition appears to be driven by compaction of the sediment, which inhibited movement of bacterial cells by reduction of porosity and pore sizes, rather than a lack of inorganic carbon or sulphates.

International audience; A synthetic pure water fluid inclusion presenting a wide temperature range of metastability (Th - Tn ≈ 50°C; temperature of homogenization Th = 144°C and nucleation temperature of Tn = 89°C) was selected to make a kinetic study of the lifetime of an isolated microvolume of superheated water. The occluded liquid was placed in the metastable field by isochoric cooling and the duration of the metastable state was measured repetitively for 7 fixed temperatures above Tn. Statistically, measured metastability lifetimes for the 7 data sets follow the exponential Reliability distribution, i.e., the probability of non nucleation within time t equals . This enabled us to calculate the half-life periods of metastability Τ for each of the selected temperature, and then to predict Τ at any temperature T > Tn for the considered inclusion, according to the equation Τs   , (∃T = T - Tn). Hence we conclude that liquid water in water-filled reservoirs with an average pore size ≈ 104 µm3 can remain superheated over geological timelengths (107s), when placed in the metastable field at 10°C above the average nucleation temperature, which often corresponds to high liquid tensions (≈ -120 -70 MPa).

International audience; A pluridisciplinary approach was used to define iodine immobilization mechanisms by biocarbonates in a natural marine carbonate-bearing clayey formation. For this purpose, different techniques of observation (optical microscope, scanning electron microscope (SEM), cathodoluminescence (CL)) and of analyses (infrared spectrometry (IR), electron microprobe (EPMA), spatially resolved synchrotron-based X-ray fluorescence (μ-XRF) and X-ray diffraction (μ-XRD)) were performed on two entire and centimeter-sized carbonate shells of the Callovian-Oxfordian (160 Ma) clayey formation from the ANDRA (French Radioactive Waste Management Agency) Underground Research Laboratory (Meuse/Haute Marne, France), in the Eastern part of the Paris Basin. Combined (SEM, CL, IR and μ-XRD) data indicates that the biostructure of the Rhynchonella shell is relatively well-preserved but bio-aragonite slowly transforms into calcite, whereas the bivalve shell is entirely recrystallized into diagenetic calcite and celestite. EPMA and μ-XRF data show bioaccumulation of iodine in carbonate shells, confirming previous work on present-day mollusks. EPMA analyses give evidence of iodine content up to 1200 ppm in the preserved Rhynchonella shell and up to 2000 ppm in recrystallized bivalve shell. μ-XRF elemental mapping shows that iodine is more homogeneously distributed in bio-calcite of the Rhynchonella shell than in recrystallized calcite of the bivalve shell, suggesting a loss of iodine during re-crystallization processes, but not a total exclusion of iodine from the carbonate structure. Combined EPMA data and μ-XRF elemental maps do not give evidence of any correlation between the iodine location and the distribution of other elements.

International audience; The metastable superheated solutions are liquids in transitory thermodynamic equilibrium inside the stability domain of their vapor (whatever the temperature is). Some natural contexts should allow the superheating of natural aqueous solutions, like the soil capillarity (low T superheating), certain continental and submarine geysers (high T superheating), or even the water state in very arid environments like the Mars subsurface (low T) or the deep crustal rocks (high T). The present paper reports experimental measurements on the superheating range of aqueous solutions contained in quartz as fluid inclusions (Synthetic Fluid Inclusion Technique, SFIT) and brought to superheating state by isochoric cooling. About 40 samples were synthetized at 0.75 GPa and 530-700 °C with internally-heated autoclaves. Nine hundred and sixty-seven inclusions were studied by micro-thermometry, including measuring the temperatures of homogenization (Th: L + V → L) and vapor bubbles nucleation (Tn: L → L + V). The Th-Tn difference corresponds to the intensity of superheating that the trapped liquid can undergo and can be translated into liquid pressure (existing just before nucleation occurs at Tn) by an equation of state. Pure water (840-935 kg m−3), dilute NaOH solutions (0.1 and 0.5 mol kg−1), NaCl, CaCl2 and CsCl solutions (1 and 5 mol kg−1) demonstrated a surprising ability to undergo tensile stress. The highest tension ever recorded to the best of our knowledge (−146 MPa, 100 °C) is attained in a 5 m CaCl2 inclusion trapped in quartz matrix, while CsCl solutions qualitatively show still better superheating efficiency. These observations are discussed with regards to the quality of the inner surface of inclusion surfaces (high P-T synthesis conditions) and to the intrinsic cohesion of liquids (thermodynamic and kinetic spinodal). This study demonstrates that natural solutions can reach high levels of superheating, that are accompanied by strong changes of their physico-chemical properties.

Mineralium Deposita, 44 (6), ISSN:0026-4598, ISSN:1432-1866

International audience; The morphologic study of the surface of Mars reveals that liquid water existed during the first few hundred millions of years of the planet's history (e.g. Smith et al. 1999). The flow of water produced extensive erosion in some place, but also large sedimentary basins. With a long enough duration of the presence of liquid water and the oxidation of basalts, the emergence of biological activity may have eventually occurred, as on Earth. The detection of biomarkers at the surface of Mars is one of the main challenges of current and planned planetary exploration missions (e.g. Westall et al. 2000). Looking for a fossil or present biological activity may be approached by the search for cells, but also by the study of the results of their activity and their interface with the sedimentary environment. Such bio-sedimentations are known among the oldest terrestrial fossils and testify to the earliest terrestrial bioactivity. A discovery of such bio-sedimentations on the Martian surface would be of prime interest for addressing some of the key goals in exobiology. Cathodoluminescence (CL) is a method relevant to the search for life, as it is in line with these analytical goals of detecting bio-sedimentations (Barbin et al. 1999), and it fits well with robotic facilities usable in modern space missions (Blanc et al. 1999, Thomas et al. 2002. 2005). An established technique, cathodoluminescence is a newcomer to Martian exploration, whereit is expected to contribute to the mineralogical characterisation of sedimentary rocks, to the search for biomarkers revealing past biological activity, and to identify past geochemical conditions (Melezhik et al. 1999; Denson et al. 2007). CL is one of the best methods when the growth dynamics, microstructure, and origin of minerals need to be determined, such as with Martian sediments. CL has become an important standard technique for studying geological materials, offering a wide spectrum of applications (Marshall 1988; Barker and Kopp 1991; Barbin and Schvoerer 1997; Pagel et al. 2000). However, it is in the field of sedimentology and petrography that CL has proved to be especially valuable.

After a thorough study on the tracing of the emerald origin by oxygen data by Zwaan et al. [12], the paper by Moine et al. [4] entitled ‘The role of fluorine in the formation of the Mananjary emerald deposits (eastern Madagascar)' demonstrates through a thermodynamic model that the metasomatic transformation of amphibolites into fluorine-enriched phlogopites was the cause for beryl precipitation. – This paper is important as it shows that fluorine can be a dominant ligand for some metals, like beryllium. As underlined by the authors, the reason for the BeF affinity in solution is that beryllium, despite the fact it is divalent, still displays a high ionic potential due to its small ionic radius. – Moine et al. [4] calculate that a fluid equilibrated with F-phlogopite (XF=0.7) at 500 °C and 2 kbar contains 275 ppm total fluorine, compared to 55 ppm dissolved in fluids buffered by wollastonite–quartz–fluorite (WQF) in the same conditions [11]. This paper therefore contributes to enlighten that fluorine-rich fluids can circulate through rocks in some natural geological settings. More precisely, it shows that rocks dominantly formed of hydrous silicates constitute a remarkable environment where are contradicted previous conclusions in the literature that “fluoride concentrations in natural hydrothermal solutions are restricted by equilibrium constraints involving fluorite, topaz and other fluoride-bearing minerals with low solubilities” (e.g., [2] and references therein). – The numerous local crystal-chemical factors that control (OH–F) exchanges in hydrous silicates (smectites, micas, amphiboles, tourmalines) are far from being understood and modelled for any given composition. However, this paper is a good illustration of the fact that, at least for a limited number of amphibole and biotite end-members with restricted Fe-free Mg-rich compositions, a thermodynamic database is now available that satisfactorily accounts for fluorination reactions. Numerous systematic structural studies of synthetic end-members have shown that some magnesian minerals like talc, phlogopite or tremolite, host the hydroxyl group in a symmetrical trioctahedral 36[Mg3] environment. Fluorination of such minerals is easy in all proportions and controlled by simple local crystal-chemical parameters. Firstly, there is no steric limitation to the complete substitution of OH− by F− in these minerals because the ionic radii of these two anions are very similar. Also, the proton exchanges one charge with the hydroxyl oxygen and is independent of any lattice atom. Such a hydroxyl group, which behaves as a separate entity, can easily be replaced by fluorine [8].

International audience; Au and W-Sn mineralization of the Schistose Domain of Galicia-Trás-os-Montes are spatially related to late hercynian granites. The Bruès (Au) and the Mina Soriana W-(Sn) deposits are studied. Both show some similarities and are assumed to form in the same tectonic and metamorphic context, on top of the granites. The role of the granite as a source for mineralizing fluids and rheological control for vein emplacement is re-adressed and discussed.

International audience; Fluid inclusions in barite and sulfide in chimneys (both active and inactive) from three hydrothermal sites of the back arc Lau basin were studied with microthermometric and isotopic methods to determine the chemistry and evolution of hydrothermal aqueous fluids. Strontium isotope compositions of sulfides from the Lau basin reflect the presence of anhydrite and barite inclusions. The 87Sr/86Sr ratios of these two sulfate minerals vary from 0.7045 to 0.7078 and are interpreted as the result of mixing between various proportions of the hydrothermal end-member and pure seawater. The microthermometric study of fluid inclusions reveals that mixing with seawater involved different kinds of aqueous fluid end-members. A high-temperature Mg-depleted end-member of high salinity (>5.5 wt % eq NaC1) was found at the Vai Lili site. A uncommon low-temperature Mg-rich end-member was also identified at the Hine Hina site in association with barite deposition. At the Vai Lili site, very low salinity fluids were produced in addition to a very saline brine (>30 wt % NaC1) that was trapped inside anhydrite precipitated from an active vent at a temperature o[ 342øC. Oxygen isotope ratios of water inclusions range from 2%0 to 4.4%0 for chalcopyrite, barite, and sphalerite minerals. The 180 enrichment and the high salinities of many fluids from the Lau basin are accounted for by the specificity of the back arc setting. This non mid-ocean ridge setting is characterized by the shallow depth of the hydrothermal systems that allows frequent unmixing of high-temperature liquids. The abundance of silicic magmas also provided magmatic fluids (including brines) that mixed with seawater-derived aqueous fluids.

We compiled the available chemical analyses of the ponded brines and of the sediment interstitial waters for the Atlantis II, Discovery, Suakin and Valdivia deeps in the Red Sea central valley, along with the DSDP data for interstitial waters of several cores in the rift axis (Sites 225–228 of Leg 23). Recent advances in the calculation of the thermodynamic properties of concentrated solutions at high temperatures and pressures allow the study of the equilibrium conditions between anhydrite and halite, and the brines. We first tested the influence of various parameters as temperature, pressure and solution composition on the calculated anhydrite saturation index in order to provide a clear criterion for equilibrium, which is assumed when the saturation index lies within 0.9 and 1.1. We found that at 62°C and 200 bar, the pressure effect on the saturation indices is of the same magnitude as that of temperature. Our calculations point to the overall undersaturation of the free brines with respect to halite. The calculated halite saturation state of the pore waters at the four DSDP sites is consistent with the mineralogical description of the sediments in which halite is not reported, except at Site 225 where the calculated undersaturation is in contradiction with the reported presence of halite at the base of the core. From the hypothesis of equilibrium between anhydrite and the pore waters in the DSDP cores, we have estimated values of the geothermal gradients off the rift axis which fall within the highest values obtained by extrapolation of direct temperature measurements. This suggests that, at the latitude of the Atlantis II and Suakin deeps, the high heat fluxes measured along the axial trough extend off the rift axis. Our calculations show that the Upper Convective Layer (UCL) of the Atlantis II hydrothermal system has always been undersaturated over the studied period (1965–1985), which is consistent with the absence of anhydrite in sediment underlying this brine. The calcium and sulfate contents of the Lower Convective Layer (LCL) show a parallel evolution: they decrease when temperature increases. Although this behaviour suggests control of brine chemistry by equilibrium with anhydrite, our calculations show that anhydrite has reached saturation in the lower brine only in 1966 and 1976. The general regime leading to the loss of calcium and sulfate outside these periods is tentatively attributed to diffusion. Calculations show that, throughout the whole stratified brine column (from the sediment to normal Red Sea water), there is no chemical potential gradient for calcium sulfate whereas the chemical potential of sodium chloride regularly decreases. We tentatively advocate the coupling of calcium sulfate diffusion with the large sodium chloride gradient to account for the loss in Ca and SO 4 . Finally, the pore water chemistry of the Atlantis II and Discovery Deep sediments record two parallel evolutions from anhydrite undersaturation in 1966 to saturation (or a state close to) in 1976. These data are consistent with a periodical brine overspill from Atlantis II into Discovery.

Phase equilibrium analysis of the relevant systems together with the application of the principles of chemical equilibrium put severe constraints on the interpretation of fluid inclusion data in terms of immiscibility (in Part I). Following from that point, the major limits on the accuracy, and even the validity, of fluid inclusion quantitative data and their interpretation in terms of fluid composition and density are briefly discussed. The practical implications of the general constraints (temperature, pressure, topology of the fluid systems) are envisaged. Emphasis is laid on some important consequences such as: the use of isochore intercepts (and the possible resulting interpretation of fluid mixing rather than unmixing), the case of highly saline inclusions, the identification and interpretation of heterogeneous trapping. The composition and density constraints on coexisting fluids are presented, and illustrated by natural examples. Taking into account all the measurable parameters in fluid inclusions (volume, temperature and nature of phase transitions, more or less complete individual spectroscopic analyses), all the available experimental data, and all the theoretical constraints, may be long and difficult. However, it is most generally very informative and productive although part of these data is often sufficient to deny unmixing. Nevertheless, a final example on metamorphic fluids demonstrates how such an approach can “prove”; and also characterize a fluid unmixing during a geologic process.

Four techniques have been selected to analyse molecular fluid phases in crystals : microthermometry (M.) and Raman Spectrometry (R.S.). non destructive ponctual techniques available only for transparent minerals ; mass spectrometry (M.S.) and gas chromatography (G.C.) available for the bulk analysis of fluids released by crushing or heating of all kinds of minerals. High temperature vein quartz from the scheelite-wolframite deposit of Jbel Aouam (Central Morocco) has been selected to be analysed by the four techniques because it contains a homogeneous generation of fluids. (1) Within the uncertainty on the measurements, molar fraction of H2O in the fluids from quartz is consistently measured by the four techniques. (2) The CO2/CH4 molar ratio obtained by R.S. is consistent with the analytical data from G.C. ; it is superior by one or two orders of magnitude to that obtained by M.S. (3) Small and constant amount of H2 is detected only by M.S. (4) Heavy carbonaceous species are systematically identified by M.S. and with less quantities by G.C. ; they are not in fluid inclusions where only CO2 and CH4 are detected by R.S. (5) However dark particles are visible under the microscope in fissures of the quartz ; their Raman scattering spectrum is similar to that of coal, therefore they still can yield hydrocarbons on heating., Quatre techniques ont été utilisées pour analyser les phases fluides moléculaires dans les cristaux : la Microthermométrie (M.) et la Spectrométrie Raman (S.R.), techniques non destructives ponctuelles utilisables seulement pour les minéraux transparents ; la Spectrométrie de masse (S. M.) et la Chromatographic en phase gazeuse (C.G.) pour l'analyse globale des fluides libérés par écrasement ou chauffage de toutes sortes de minéraux. Une veine de quartz de haute température à scheelite et wolframite provenant du Jbel Aouam (Maroc Central) a été choisie pour cette étude en raison de l'homogénéité de ses fluides inclus. (1) La fraction molaire en H2O est la même pour les quatre méthodes dans la marge d'erreur des mesures. (2) Le rapport molaire CO2/CH4 obtenu par S.R. est conforme à celui trouvé en C.G. ; il est une à deux fois plus grand par S. M. (3) De petites quantités constantes de H2 n'ont été détectées qu'en S. M. (4) Des espèces carbonées lourdes sont systématiquement identifiées par S. M. et en quantités moindres par C.G. ; elles ne se trouvent pas dans les inclusions fluides où seuls le CO2 et le CH4 sont détectés par S.R. (5) Par contre des particules noirâtres sont microscopiquement visibles dans les fissures du quartz ; leur spectre de diffusion Raman montre qu'elles sont du type charbon et peuvent avoir une capacité importante de libération d'hydrocarbures., Cheilletz Alain, Dubessy Jean, Kosztolanyi Charles, Masson-Perez Nicole, Ramboz Claire, Zimmermann Jean-Louis. Les fluides moléculaires d'un filon de quartz hydrothermal : comparaison de techniques analytiques ponctuelles et globales, contamination des fluides occlus par des composés carbonés. In: Bulletin de Minéralogie, volume 107, 2, 1984. Inclusions fluides.

Aqueous inclusions in oil-bearing vug-filling barite which postdates the karstic and fissural ore stages at Les Malines, one of the largest Mississippi Valley-type Zn-Pb deposits in Europe, have been studied by microthermometry and Raman spectrometry. The correlative variations of the melting points of ice (T (sub m ice ) and of the homogenization temperatures (T h define three main stages: (1) stage I, gas-rich inclusions characterized by T (sub m ice ) = -7 degrees + or - 1 degrees C and T (sub h (sub L-V(V)) ) = 180 degrees to 380 degrees C, (2) stage II, liquid-rich and gas-rich inclusions homogenized in the temperature range of 160[degree to 175 degrees C, with T (sub m ice ) = -8.2 degrees to -4.1 degrees C--stage I and stage II inclusions contain CO 2 and no CH 4 , N 2 , or H 2 S detectable by Raman spectrometry, and (3) stage III, liquid-rich inclusions, characterized by T (sub m ice ) which increased from -8 degrees to -1.7 degrees C as their T (sub h (sub L-V(L)) ) decreased from 160 degrees to 130 degrees C. They are essentially aqueous.The H 2 O-CO 2 -NaCl vapor-dominant stage I inclusions in barite cannot have leaked because their gas content is distinct from air. They are interpreted to have trapped a hot (T approximately 300 degrees C), CO 2 -bearing vapor which was cooling. Oil was thermally degraded during trapping in barite. The source of heat and CO 2 is considered to be volcanism contemporaneous with the major uplift of the horst during the Upper Jurassic, Dissolution of the carbonated wall rock is related to stage I. Stage II inclusions are interpreted to represent the end-product of the mixing of pore fluid with the hot vapor. The temperature of the pore fluid exceeded 150 degrees prior to the addition of magma-heated fluids. Such anomalous pore fluid temperatures are tentatively related to the steady dewatering of the Terres Noires shales from below, with the fluids moving up along the east-west fault of Les Malines near adiabatic conditions. The formation waters were probably responsible for the migration of the oil and for the recrystallization of the basement. Gas-rich and liquid-rich stage II inclusions are compatible with minor unmixing of the H 2 O-CO 2 -NaCl liquid with precipitation of calcite. The V-X properties calculated for a stage II liquid-rich inclusion (96.1 mole percent H 2 O, 1.85 mole percent NaCl, and 2 + or - 0.2 mole percent CO 2 ; V = 21.5 + or - 1.3 cm 3 mole (super -1) fix the pressure of unmixing at 175 degrees C in the range 285 + or - 45 bars. The T h -V-X properties of secondary CO 2 -bearing inclusions in barite from the earlier fissural stage (Charefand Sheppard, 1988) point to higher fluid pressures in the horst, in the range of 365 + or - 45 bars minimum. CO 2 -rich inclusions in the two barite generations imply that the metamorphosed Cambrian basement at Les Malines has been transiently geopressured below the Triassic shales. The addition of a small amount of magma-derived CO 2 to the pore fluid probably accounts for the rapid increase of pressure. The fluid pressure in the horst reached near-lithostatic values repetitively, first at the end of the Middle Jurassic subsidence, when the burial depth was around 1,600 + or - 200 m, then at a later stage, probably during the Upper Jurassic, when the sedimentary cover was partly eroded to around 1,200 + or - 200 m. The overpressuring, with a possible structural deformation resulting from the rising magma, probably caused the opening of the vertical, late barite-filled veins by hydraulic fracturing. Stage III inclusions are interpreted to indicate the influx of colder diluted fluid to the horst under hydrostatic pressure conditions, i.e., after decompression.

The aim of this paper is to determine the physical and chemical parameters which control the opposite behaviour of uranium and tin-tungsten between 300° and 500 °C. In uranium deposits, fO2 and fS2 of mineralizing fluids are higher than values fixed by the pyrite-hematite-magnetite triple point, as shown by uraninite-hematite and/or pyrite mineral association. The stability of quartz-K feldspar-muscovite paragenesis in the wall-rocks of hydrothermal U deposits indicates weakly acid pH. By contrast, in the Sn-W occurrences from the French Southern Massif Central, the fO2 of mineralizing fluids is between Ni-NiO and Q-F-M buffers as shown by CO2-CH4-H2O-NaCl bearing fluid inclusions. The pH of these fluids is weakly acid to weakly basic as shown by the stability of muscovite in presence or absence of quartz and/or feldspar. Sn-W mineralizing fluids from Cornwall are by contrast purely aqueous and acid, as indicated by the mineral assemblage muscovite-quartz which is typical of greisens. Experimental data on UO2, SnO2, FeWO4, CaWO4 solubility and metal species in fluids show that fO2 > H-M are required for uranium transport whereas fO2 ≤ Ni-NiO favours Sn transport. The fluid oxidation state has no direct influence on the transport and deposition of tungsten. The fO2 control on the hydrothermal transport properties of these three metals is related on the one hand to the fluid and rock composition, and on the other hand to the minimal 320 °C temperature required for homogeneous equilibria in the C-O-H system to control the oxidation state at low values. At high temperatures, Sn, Fe and Ca chloride complexes are more stable than carbonate and phosphate uranium complexes ; this is attributable to their structure and to the dielectric content of the fluid. The presence of dissolved gases at high concentration, which are produced by devolatilization reactions at high temperatures, is emphasized since they lower the dielectric constant of the fluid which enhances the stability of chloride complexes. All these results show that temperature and fO2 account for the opposite behaviour of uranium and tin-tungsten in hydrothermal systems between 300° to 500 °C., Le but de ce travail est de déterminer les paramètres physico-chimiques qui contrôlent le comportement antagonique de l'uranium et de l'étain-tungstène entre 300° et 500 °C. Dans les gisements d'uranium, les fO2 et fS2 des fluides minéralisateurs sont supérieures à celles fixées par le point triple pyrite - hématite - magnétite comme le montre l'association uraninite - hématite - et/ou pyrite. La stabilité de la paragenèse quartz - feldspath potassique - muscovite dans les roches encaissantes des minéralisations uranifères considérées témoignent de pH faiblement acides. En revanche, pour les minéralisations à Sn-W du sud du Massif Central français, la fO2 des fluides minéralisateurs est comprise entre les tampons Ni-NiO et Q-F-M comme l'indiquent les inclusions fluides à CO2-CH4-H2O-NaCl. Le pH de ces fluides est faiblement acide à faiblement basique comme le montre la stabilité de la muscovite en présence ou en absence de quartz et/ou de feldspath. Les fluides minéralisateurs en Sn-W de Cornouailles sont, au contraire, purement aqueux et acides, comme l'indique l'assemblage muscovite - quartz typique des greisens. L'analyse des données expérimentales de solubilité de UO2, SnO2, FeWO4, CaWO4 et de spéciation des métaux montrent que des fO2 ≤ Ni-NiO favorisent le transport de l'étain. L'état d'oxydation du fluide n'a aucune influence directe sur le transport et le dépôt du tungstène. Le contrôle de la fO2 sur les capacités de transport hydrothermal de ces trois métaux est mis en relation d'une part avec la composition des fluides et des roches, d'autre part avec la température minimum de 320 °C requise pour que les équilibres homogènes du système C-O-H fixent l'état d'oxydation à des valeurs basses. A haute température, la stabilité accrue des complexes chlorurés de Sn, Fe, Ca comparée à celle des complexes carbonatés et phosphatés d'uranium est discutée en fonction de la structure des complexes, et de la constante diélectrique du fluide. On souligne également que la présence de gaz dissous (concentration élevée), produits à haute température par les réactions de dévolatilisation, diminue la constante diélectrique du fluide et stabilise corrélativement les complexes chlorurés. L'ensemble de ces résultats montre que la température et la fugacité d'oxygène rendent compte du comportement antagonique de l'uranium et de l'étain - tungstène au stade hydrothermal entre 300° et 500 °C., Dubessy Jean, Ramboz Claire, Nguyen-Trung Chinh, Cathelineau Michel, Charoy Bernard, Cuney Michel, Leroy Jacques, Poty Bernard, Weisbrod Alain. Physical and chemical controls (fO2,T,pH) of the opposite behaviour of U and Sn-W as examplified by hydrothermal deposits in France and Great-Britain, and solubility data. In: Bulletin de Minéralogie, volume 110, 2-3, 1987. Les mécanismes de concentration de l'uranium dans les environnements géologiques.

The microthermometric study of the fluid inclusions from the Southwest Tintic District has confirmed that the copper mineralization can be related to the porphyry type deposit. In addition, the major stages of the hydrothermal activity have been determined. At the late magmatic-early hydrothermal stages (700° C and about 2 kbar), circulated high salinity brines, containing mostly KCl and NaCl, with high copper contents (1,000 to 2,000 p. p. m. Cu). The adiabatic decompression resulted in the boiling of the fluids, starting at about 600° C and 800 bar. The fluid phases became supersaturated with respect to chalcopyrite, yielding the deposit. — The fluids continued to boil as pressure and temperature decreased rapidly, and the brines became supersaturated in halite as well. — Boiling stopped as the pressure decreased to about 100 bar. Liquids of lower salinity were finally trapped at and below 400° C., L'étude microthermométrique des inclusions fluides a confirmé que la minéralisation de Southwest Tintic se rattache au type porphyre cuprifère, et a permis en outre de dégager ses caractères spécifiques : — Le début de l'activité hvdrothermale est marqué par la circulation de saumures riches en NaCl, KCl et, entre autres, en chalcopyrite (1 000 à 2 000 p. p. m. Cu) vers 700° C, à une pression de 2 à 3 kbar. — Une phase de décompression adiabatique se produit, qui provoque la mise en ébullition des fluides vers 600° C, 800 bar. On constate que les fluides ont été saturés en chalcopyrite au cours de la phase d'ébullition. Ce sont ces solutions sursaturées en cuivre qui déposent l'essentiel de la chalcopyrite qui constitue le gisement. — L'ébullition se poursuit alors que la pression et la température décroissent rapidement : les saumures sont alors également saturées en halite. — La fin de l'activité hydrothermale est marquée par l'arrêt de l'ébullition, à des pressions de l'ordre de 100 bar : les fluides alors piégés vers 400° C et au-dessous sont des liquides de salinité plus faible., Ramboz Claire. A fluid inclusion study of the copper mineralization in Southwest Tintic District (Utah). In: Bulletin de Minéralogie, volume 102, 5-6, 1979. Minéraux et minerais.

International audience; Contraindre l’histoire thermique des secteurs d’exploration et de prospection minière permet de mieux comprendre et prédire les processus de minéralisations et ainsi, d’établir des modèles métallogéniques nécessaires à l’évaluation des ressources minérales. La reconstitution des paléo-champs de températures associées aux processus minéralisateurs nécessite le couplage de plusieurs données analytiques telles que les données structurales, thermiques et géochimiques.

International audience; Copper mineralization in sedimentary cover is well known in association with Pb and/or Zn in Sedex, Kupferschiefer, Mississippi Valley-Type, or Red bed deposits. In spite of great economic potential, the syngenetic versus epigenetic origin of widespread Cu occurrences in the Adoudounian sedimentary cover, in the Moroccan Anti Atlas, remains debated. Significant investigations that would provide critical information for mining exploration are lacking. Whatever their origin, these mineralizations do not correspond to classical sediment-hosted deposits, the ore being exclusively Cu concentrations in dolostone units. This study, based on field and microscopic observations, is focused on Cu mineralization hosted in the Adoudounian cover of the Bou Azzer-El Graara inlier. Two morphologic types of ore bodies exist. The first consists of stratabound lenses and the second type is vein networks along Variscan faults. Both types of mineralization have a stockwork texture and clearly postdate sedimentary fabrics, such as beddings and slumps; this suggests a common epigenetic origin for the both ore types. The proposed interpretation involves the upflow of Variscan fluid-driven interaction between a basement and its sedimentary cover.

In order to prepare for the next in situ missions to Mars (MSL-2011 and ExoMars-2018), the objective of my thesis is to create a collection of relevant analogue rocks and minerals for calibrating and testing future (and existing) space flight instruments, in accordance with the geology of Mars. They were characterized using standard laboratory instrumentation (optical microscopy, Raman, IR, XRD, SEM, electron microprobe and ICP-MS), as well as by flight instrumentation in development (Mössbauer MIMOSII, ExoMars Raman and IR (MicrOmega) spectrometers). All the samples are described in an online database in the following web site: www.isar.cnrs-orleans.fr. A part of this thesis is dedicated to the development of a cathodoluminescence (CL) instrument that could potentially be adapted for space flight. Study of alteration processes of basalts on Earth that show some similarities to surface and subsurface processes occurring on Mars may help understand and interpret martian features. Therefore, to complete the collection, samples of hydrothermal and acidic weathered basalts were collected from the Skouriotissa mine in Cyprus. The mineralogical evolution of the basalt through different alteration facies was studied. Because terrestrial basalts are poorer in Fe and Mg than martian basalts, I synthesized two artificial martian basalts. The two artificial basalts are different in terms of cooling rate (~110°C/h and drop-quenched, >1200°C/h). Interestingly, the more slowly-cooled sample exhibits a spinifex texture, similar to that of komatiites. If similar basalts occur on Mars, such rocks when altered by aqueous processes may have astrobiological implications.; L'objectif de la thèse est de créer une collection de roches et minéraux analogues pour calibrer et tester les futurs (et existants) instruments de vol, en accord avec la géologie de Mars afin de préparer les futures missions in situ (MSL-2011 et ExoMars-2018). Les échantillons sont caractérisés avec des instruments de laboratoire (microscope, Raman, IR, DRX, MEB, microsonde électronique, et ICP-MS), mais aussi avec des instruments de vol en développement (Mössbauer MIMOS II, les spectromètres ExoMars Raman et IR (MicroOmega)). L'ensemble des échantillons sont décrits sur une base de données en ligne à l'adresse : www.isar.cnrs-orleans.fr. Une partie de cette thèse est dédiée au développement d'un instrument de cathodoluminescence, qui peut être adapté au spatial. L'étude des processus d'altération des basaltes sur Terre montrant des similarités avec les processus de surface et de subsurface présent sur Mars, permet d'aider à mieux comprendre et interpréter les objets sur Mars. Pour cela, et pour compléter la collection, des basaltes altérés dans des conditions hydrothermales et acides ont été collecté dans la mine de Skouriotissa à Chypre. L'évolution minéralogique des basaltes à travers les différents facies d'altération a été étudiée. Parce que les basaltes terrestres sont plus pauvres en Fe et Mg que les basaltes martiens, deux basaltes artificiels ont été synthétisé. Ces deux échantillons sont différents en terme de refroidissement (~110°C/h et trempé). On note que le basalte refroidi lentement montre des textures spinifex similaires aux komatiites. Si ce type de basalte est présent sur Mars, et altéré en présence d'eau, ceci peut avoir d'importantes implications exobiologiques.

Stretched (tensile) liquid water is a metastable liquid which persists at negative pressures in the stability field of vapour. The lifetime of metastability is limited. Tensions down to - 1400 bar have been specifically measured in aqueous inclusions inside quartz monocrystals. Vapour nucleation (Tn) marks the end of metastability. The destructive effects related to vapour nucleation in transiently tensile fluids are observed in nature: phreato-magmatic explosions, geysers. Modelling the kinetics of tensile water is critical in order to control the risks associated to metastable liquids. Quartz-hosted synthetic fluid inclusions (FI) with known densities and chemistries have been placed into the metastable tensile field by isochoric cooling and their Tn have been measured. We show that the tensile strength of water in individual FI depends on the FI volume and shape, the method used to synthetize the FI and the fluid chemistry. Experiments on metastability lifetimes have been performed by placing FI at temperatures 0.5° to 10°C above th eir Tn. Eigth FI were chosen that encompass the diversity of FI volumes, shapes, densities, fluid chemistries and tensile strengths. Our results show that tensile water lifetimes are all the shorter as the trapped water is more stretched. An empirical kinetic law is proposed that allows the lifetimes of tensile water in FI to be calculated as a function of the FI volume and Tn. Our data can also be reconciled with the Classical Nucleation Theory. Our data finally show that water in natural porous reservoirs can remain stretched for geologically-relevant timescales. Tensile water can therefore control fluid-rock interactions in the continental crust., L'eau tensile est de l'eau liquide métastable qui persiste dans le champ de stabilité de la vapeur à pression négative, sa durée de vie est finie. Des états de traction de l'eau jusqu'à -1400 bar ont été mesurés de façon spécifique dans des micro-inclusions intracristallines. La nucléation de vapeur (Tn) marque le retour à l'équilibre. Les effets destructeurs liés à la rupture d'états transitoires d'eau tensile sont observés dans le milieu naturel : explosions phréato-magmatiques, geysers. Modéliser la cinétique de l'eau métastable est fondamental pour gérer les risques qui lui sont associés. Des inclusions fluides synthétiques (IF) de composition et de densité connues, piégées dans du quartz, ont été placées dans le champ métastable par refroidissement isochore et leurs gammes de métastabilité ont été mesurées. On montre que la traction maximale de l'eau dans chaque IF dépend de son volume et de sa forme, de la méthode de synthèse de l'IF, de la chimie des solutions occluses. Des expériences de durée de vie ont été ensuite réalisées sur des IF placées de 0,5° à 10°C au-dessus de leurs Tn. Les 8 IF choisies rende nt compte de la diversité des formes, des volumes, des densités et gammes de traction observées. Les résultats montrent que la durée de vie de l'eau tensile en IF est d'autant plus courte que la traction de l'eau est plus forte. Une loi empirique est proposée qui permet de calculer la durée de vie de la métastabilité pour chaque IF de Tn et volume fixés. Par ailleurs, nos données peuvent être rendues compatibles avec la Théorie Classique de la Nucléation. Nos résultats montrent que l'eau dans les réservoirs poreux naturels peut rester métastable pendant des durées géologiques et ainsi, contrôler les interactions fluides-roches dans la croûte.

Study of natural CO2 analogues brings key informations on the factors governing the long term stability/instability of future anthropogenic CO2 storages. The main objective of this work, through the study of cores from V.Mo.2 well crosscutting the Montmiral natural reservoir (ValenceBasin, France), is to trace the deep CO2 migrations in fractures. Petrographic, geochemical and icrothermometric studies of the V.Mo.2 cores were thus performed in order: 1) to describe the reservoir filling conditions and 2) to detect possible CO2-leakage through the sediments overlying the reservoir. Fluid inclusions from the Paleozoic crystalline basement record the progressive unmixing of a hot homogeneous aquo-carbonic fluid. The Montmiral reservoir was therefore probably feeded by a CO2-enriched gas component at the Late Cretaceous-Paleogene. The study of the sedimentary column in V.Mo.2 well, demonstrates that the CO2 did not migrate towards the surface through the thick marly unit (Domerian-Middle Oxfordian). These marls have acted as an impermeable barrier that prevented the upward migration of fluids. Two main stages of fluid circulation have been recognized: 1) an ante-Callovian one related to the tethysian extension 2) a tertiary stage during which the upper units underwent a karstification, with CO2 leakage related but which remained confined into the deeper parts of the Valence Basin. Since the Paleogene, the Montmiral reservoir has apparently remained stable, despite the pyrenean and alpine orogeneses. This is mainly due to the efficient seal formed by the thick marly levels and also to the local structuration in faulted blocks which apparently acted asefficient lateral barriers.; Le stockage géologique du CO2 est un des enjeux scientifiques majeurs envisagés pour contrôler le réchauffement climatique lié aux gaz à effet de serre. Le stockage en domaine sédimentaire nécessite une connaissance des facteurs stabilisant/destabilisant les réservoirs, qui peut être apportée par l'étude d'analogues naturels. L'utilisation de méthodes pétrographiques, microthermométriques et géochimiques appliquées aux carottes du forage V.Mo.2 traversant le réservoir naturel de CO2 de Montmiral (France), permettent de suivre les migrations de CO2. Dans le socle Paléozoïque, les inclusions fluides carboniques témoignent de la démixtion sous forte couverture d'un fluide aquo-carbonique chaud, probablement à la fin du Crétacé ou au Paléogène, qui marquerait le remplissage du réservoir de Montmiral. L'étude des unités sédimentaires sus-jacentes montre que le CO2 est resté confiné dans les niveaux rhéto-sinémuriens sous les marnes du Domérien à l'Oxfordien Moyen. Ces marnes jouent le rôle de barrière étanche aux fluides au cours des principaux stades de circulations reconnus. Un premier stade lié à l'extension téthysienne affecte les séries sous-jacentes aux marnes. Un deuxième stade, rattaché à la compression pyrénéenne grâce à une étude de terrain, induit une karstification des séries sus-jacentes à l'écran marneux. A la base du forage, c'est à cette période que le réservoir fuit, mais cette fuite reste confinée sous l'écran marneux. La stabilité du réservoir de Montmiral est due à la présence de l'épais niveau marneux et à la structuration en blocs du bassin de Valence et de son socle limités par des failles jouant le rôle de barrière latérale.

This thesis presents the reconstruction of the tectono-thermal history of the Paleozoic Jebilet massif (Morocco), from its pre-orogenic evolution at the Upper Devonian-Lower Carboniferous to its structuration during the variscan-alleghanian orogeny at the Upper Carboniferous-Lower Permian. To address this issue, this work is organized around two approaches: (1) one metrological applied to the Raman Spectroscopy of Carbonaceous Matterial (RSCM) and (2) the other integrating a structural and geochronological study and a thermicity analysis.The metrological approach allowed to validate the applicability of the RSCM geothermometer (1) in a context of polyphase metamorphism, (2) for carbonate rocks and skarns of Jebilet and (3) to propose a new parameter Raman RSA allowing to better specify temperatures above 500°C and extend the applicability of the method to maximum temperatures of up to 700°C.From the integrated approach, three tectono-thermal episodes were highlighted. The first episode D₀, corresponds to an extensive tectonic allowing the opening of the Jebilet basin at the Upper Devonian-Lower Carboniferous. This opening is accompanied by a HT thermal anomaly as shown by the important bimodal and granodioritic magmatic activity dated between 358 ± 7 Ma and 336 ± 4 Ma and the TRSCM higher than 500°C recorded by the rocks. During Upper Carboniferous, the compressive phase structuring the Jebilet massif begins with the emplacement of superficial nappes (D₁), followed by the variscan major phase (D2). Structural analysis showed a gradual evolution of D₂ deformation regime from coaxial compression to dextral transpression consistent with WNW-ESE to NW-SE horizontal shortening. D₂ is associated with two thermal events, the first is syn-tectonic with TRSCM between 300 and 400°C, and the second is syn- to post-tectonic with TRSCM between 600 and 660°C.This tectono-thermal context would be the expression of geodynamic processes involving from the Upper Devonian a delamination of the Rheic lithosphere by "slab break-off" or "slab roll-back" which would induce (1) the rise of hot asthenospheric current, and (2) the clockwise rotation of Gondwana and its gradual amalgamation with Laurussia structuring the variscan-alleghanian belt during the Upper Carboniferous-Lower Permian.; Cette thèse présente la reconstruction de l’histoire tectono-thermique du massif varisque des Jebilet (Maroc) à fort potentiel minier, depuis son évolution pré-orogénique au Dévonien supérieur-Carbonifère inférieur jusqu’à sa structuration pendant l’orogénèse varisque-alléghanienne au Carbonifère supérieur-Permien inférieur. Pour répondre à cette problématique, ce travail s’organise autour de deux approches : (1) l’une métrologique appliquée à la géothermométrie Raman sur la matière carbonée (RSCM) et (2) l’autre intégrant une étude structurale, géochronologique et une analyse de la thermicité.L’approche métrologique a permis de valider l’applicabilité du géothermomètre RSCM (1) dans un contexte de métamorphisme polyphasé, (2) pour des roches carbonatées et des skarns des Jebilet et (3) de proposer un nouveau paramètre Raman RSA permettant de mieux préciser les températures supérieures à 500°C et d’étendre l’applicabilité de la méthode jusqu’à des températures maximales qui atteignent les 700°C.A partir de l’approche intégrée, trois épisodes tectono-thermiques ont été mis en évidence. Le premier épisode D₀ correspond à une tectonique extensive permettant l’ouverture du bassin des Jebilet au Dévonien supérieur-Carbonifère inférieur. Cette tectonique extensive est accompagnée par une anomalie thermique supérieure à 500°C déduites des mesures de géothermométrie RSCM (TRSCM) et par une importante activité magmatique bimodale et granodioritique datée dans ce travail entre 358 ± 7 et 336 ± 4 Ma. Au Carbonifère supérieur débute la phase compressive structurant le massif des Jebilet avec la mise en place de nappes superficielles au Namuro-Westphalien (D₁), suivie par la phase varisque majeure (D₂). L’analyse structurale a permis de montrer une évolution progressive du régime de déformation de D2 depuis une compression coaxiale à une transpression dextre compatible avec un raccourcissement horizontal WNW-ESE à NW-SE. D₂₁ est associée à deux événements thermiques, le premier syn-tectonique de moyenne température (300°