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International audience; Late-Hercynian Intrusion-related gold deposits: an integrated model on the Tighza polymetallic district, central Morocco, African Earth Sciences (2015), doi: http://dx.Gold have been recently recognized in the Tighza (formerly Jebel Aouam) district, in the Hercynian belt of central Morocco. This district has long been known for its W mineralization, as well as major Pb-Ag-Zn, and minor Sb-Ba deposits, all geographically associated with late-Hercynian calc-alkaline magmatism. Gold mineralization in the district is mainly hosted by thick W-Au quartz veins located around the “Mine granite” small granitic plug. Within the veins, gold grade is highest (up to 70 g/t) close to the granite but rapidly decreases going outward from the granite, defining a perigranitic zoning. Anomalous gold grades have also been measured in hydrothermal skarn layers close to two other granitic plugs (Kaolin granite and Mispickel granite), associated with disseminated As-Fe sulfides. The paragenetic sequence for the W-Au quartz veins shows three stages: 1) an early oxidized stage with wolframite-scheelite associated with early quartz (Q1), 2) an intermediate Bi-As-Te-Mo-Au sulfide stage with loellingite, bismuth minerals and native gold with a later quartz (Q2), restricted to a narrow distance from the granite, and 3) a late lower temperature As-Cu-Zn–(Pb) stage with abundant massive pyrrhotite, arsenopyrite and sphalerite, locally forming independent veins (“pyrrhotite vein”). Both Q1 hyaline and Q2 saccharoidal gold-bearing quartz display aqua-carbonic fluids with minor H2S and Cu and an homogeneous composition (81 mole% H2O, 18 mole% CO2 and about 1 mole% NaCl). The trapping pressure is estimated to 1.5 to 2 kbar with temperature ranging from 300° to 350°C. Q1 inclusions have exploded indicating an uplift of the Tighza block, that lead to saccharoidal Q2 quartz deposition with multiphase NaCl-saturated fluid inclusions. 40Ar/39Ar dating demonstrates that the “Mine granite”, tungsten skarnoid, scheelite-molybdenite veins, and very likely gold-bearing veins are coeval, emplaced at 286 ± 1 Ma. Multiple and widespread metal sources are indicated by radiogenic isotope studies. Nd and Sr isotope compositions of scheelite and granites suggest the participation of a juvenile component while lead isotopes demonstrate a major participation of the basement.Both gold mineralization and zoning suggest that the system developed at the end of the magmatic activity, accompanying a major transition in magmatic fluid composition. The morphology of the gold-bearing mineralization is dependent of the permeability and the reactivity of host-rocks: focus circulation of fluids through pre-existing tectonic corridors, reactivated by late-Hercynian intrusions favor the formation of large W-type gold veins, while infiltration of fluid within reactive stratigraphic layers gives rise to skarn mineralization. A 40Ar/39Ar date (W1 north vein: 291.8 ± 0.3 Ma) indicates that hydrothermal circulation predates gold and tungsten deposition in open fractures as well as Mine granite emplacement.The W-Au mineralization preceded the onset of a large convective hydrothermal cell around the intrusion that led to the formation of the Pb-Ag-Zn mined veins. The Tighza polymetallic district displays numerous similarities with the R-IRG model that was defined in the American Cordillera, such as thermal and zonation patterns, carbonic hydrothermal fluids and chronology of intrusion and related deposits, but also provides new insight to the R-IRG model such as wide Au-quartz veins instead of sheeted Au-veins, oxidation state of the magma, and Sr-Nd isotopic data. These results establish a major magmatic contribution and discard a direct genetic relationship between gold mineralization and major neighboring Pb-Ag-Zn veins. A large number of classic Pb-Zn district of the Western Hercynides belong to the same clan.

International audience; The knowledge of the thermal history of rocks is a key point for reconstructing the history of basins or mountain belts for mining or petroleum industries. Conventional techniques such as mineralogy, isotopic analysis, provide basic data concerning the maturity degree of organic matter. Recent new geothermometric approach based on the Raman Spectroscopy of Carbonaceous Materials (RSCM) has been developed. This approach allows successfully estimating peak temperatures of advanced diagenesis to high-grade metamorphic rocks. The aim of this study is mainly to apply the RSCM geothermometry for 3D paleotemperatures cartography in the Guemassa area, a Hercynian massif located at 35 Km SW of Marrakech, Morocco. This area composed of the carboniferous metasediments, underwent tectonic, metamorphic and hydrothermal events that explain the presence of several base metal deposits like Zn-Pb-Cu Hajjar mine. Combining RSCM data and classical methods of thermometry like fluid inclusions and chlorite thermometry will allow a good understanding of thermal history of Hajjar deposits. The samples used in this study were collected around the Hajjar mine and from different depths in the Hajjar body collected in the footwall and hangingwall of the massive ore. Our peak temperature estimates show values superior to 500°C. These temperatures differ from the ones obtained by other classical methods, which are not higher than 450°C. Nevertheless, fluid inclusion homogenization temperatures of 450°C represent minimum trapping temperature conditions, since the fluids were trapped above boiling conditions. Also, 450°C represents minimum thermic condition for the biotite isograd. Higher Raman temperatures obtained in this work confirm the hypothesis of a late heat flow related to a deep granitic intrusion. This intrusion could be closer to the Hajjar deposit which would explain the higher Raman temperature around the mineralization. It is important to properly evaluate the consequences of this high late heat flux on the Hajjar mineralization, as it may have caused the recrystallization of the ore, with an increase of the particle size related. This thermal event could also have generated new mineralizing fluids. That is why future work will include the acquisition of complementary geochemical, chronological and structural data to better explain these high temperatures and to analyse their impact on the mineralization and their possible link with different mineralization processes.

International audience; We give arguments showing that the Pb Ag Ba F Tl anomalies on the 200 Ma paleo-(sub)surface in western Europe likely have an impact-driven epithermal origin. We propose that they derive from the dust cloud induced by a bolide fall at Rochechouart (NW French Massif Central, France), then removal by rain and percolation along reactivated crustal lineaments. Coeval alterite formation resulted from a greenhouse effect related, and favoured Ba and Pb release from feldspars. I Introduction Impact events are now well recognized as important markers of terrestrial geological history, as well as objects of prime economic potential. World class ore deposits are directly or indirectly related to giant (>130 km-wide) meteorite craters, e.g., the Sudbury Cu-Ni-PGM ores or the Witwatersrand Au-U mineralizations in Paleoproterozoic cratons (Pirajno 2009). At the scale of North America, the current worth of impact-related valuable substances has been estimated to $5 billion per year (Grieve and Masaitis 1994). In hypervelocity impact craters, a huge amount of kinetic energy is converted to heat. Target rocks are partly molten and vaporized, they are brecciated and comminuted as a compression wave propagates through them. Hot and permeable fall back and fall out ejecta as well as impact-induced fractures below and around the crater are thus favourable settings for post-impact hydrothermal circulations. Based on mineralogy, geochemistry and fluid modelling, the concentrations of Au, U, Pb-Zn sulfides to be found in crater rocks are shown to result from long duration fluid flows (10 3 s to 10 6 years), which extend at the crater-scale and deeper than 1 km below it (e.g., Komor et al. 1988; Naumov 2005). It may seem paradoxical that, whereas terrestrial meteorite impacts may cause global environmental catastrophes (Pierazzo and Artemieva 2012), the economic potential of an impact has seldom been documented to extend at a continental scale so far. In France, the economic importance of the Hettangian paleosurface has long been recognized (e.g., Samama 1980; Lhégu and Touray 1980), but no single unified metallogenic model was ever proposed to account for the complex interplay of hydrothermal and continental weathering processes on this paleosurface. Recently, Schmieder et al. (2010) suggested that some Hettangian Pb-Zn-U-F-Ba mineralizations could be related to the Rochechouart crater (RC), based on their new dating of the impact at 201±2 Ma. Figure 1a shows the crater, ≈ 20km in diameter, located on the NW margin of the French Massif Central (FMC) part of the Variscan belt and on the NE edge of the Aquitaine basin. It affected a mixed crystalline target primarily composed of granitic, metamorphic and intrusive igneous rocks of the Variscan orogeny (Lambert 1977, 2010; Chévremont et al. 1996). In this context, we review and discuss some metallogenic and high-energy environmental effects recorded in the lower Hettangian (LH) of western Europe (WE), in the scope of the Rochechouart impact.

International audience; This study aims at precising the thermal history of the Guemassa massif and that of the Hajjar polymetallic deposit, by using a recently-developed method: the Raman Spectroscopy of Carbonaceous Material (e.g. Beyssac et al 2002; Lahfid et al 2010). The Guemassa massif belongs to the Moroccan Meseta domain and is mainly composed of Palaeozoic rocks folded during the Hercynian orogeny. This area underwent tectonic, metamorphic and hydrothermal events that explain the presence of several base metal deposits like Hajjar. The application of Raman Spectroscopy of Carbonaceous Material geothermometry (RSCM) has revealed new temperature peaks superior to 500°C that were unrevealed by other methods (fluid inclusion, chlorite thermometry). This new data set will allow a better understanding of the thermal history and of the mineralization processes in the Guemassa massif.

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

Communication Orale; International audience; Fluids present in the depths of subduction zones play a major role on seismogenesis, although fluid circulations paths and physico-chemical conditions are still largely unknown. Two main reservoirs of water, either in the pores of sediments or bound to hydrous minerals, release large amounts of water in the relatively shallow and deep domains of subduction zones, respectively. The usual model of circulation assumes then a bottom-up circulation driven by fluid pressure gradients. This study aims at reassessing this model, using the record of rocks from a paleo-accretionary prism, the Shimanto Belt in Japan. These rocks, buried to 5kbars and 300˚C (Toriumi and Teruya, Modern Geology, 1988), were affected by pervasive fracturing throughout their history, from burial to exhumation. The quartz filling these fractures and the fluid inclusions that it contains keep the track of the fluid associated with the rock evolution. Using a combined approach of microstructural observations by optical microscopy and cathodoluminescence (CL), and chemical characterization by electron and ion microprobe as well as microthermometry, we show that there are actually two distinct fluids that have cyclically wetted the rock at depth. The first one is an " external " fluid penetrating through macroscopic fractures and precipitating a quartz blue in CL. In contrast, a " local " fluid attended the formation of quartz brown in CL, precipitating in microfractures or associated with ductile recrystallization. The two fluids are also chemically distinct: Both have a salinity close to seawater, but the local fluid is fresher than the external one. In addition, the external fluid is richer in aluminum than the local one. Finally, the external fluid is very slightly depleted in δ 18 O, although the difference is probably not significant and the first-order isotopic signal is a buffering by host rock.

National audience; L’analyse des inclusions fluides dans les paléo-zones de subductionmontre que jusqu’à 300°C le fluide baignant la roche est un mélanged’eau salée et d’une faible quantité de méthane. La présence dans denombreux exemples de deux types d’inclusions (riche en eau et richeen méthane) implique l’immiscibilité du méthane dans l’eau en profondeur.Par ailleurs, les inclusions riches en méthane du paléoprismed’accrétion Shimanto, au sud-ouest du Japon, enregistrent des fortes etrapides variations de pression de fluide. Une hypothèse est que ces variationsbrutales reflètent l’enregistrement par le fluide d’un événementsismique, qui connecterait des poches de liquide isolées et ferait chuterla pression de fluide. A ce mécanisme d’enregistrement passif desséismes par les fluides, nous proposons d’ajouter un mécanisme actif,par lequel le fluide entretient la rupture sismique. En effet, lorsque lefluide acqueux est saturé en méthane, une petite chute de pression defluide, associée par exemple à un séisme, provoque une ébullition explosivedu méthane susceptible de fracturer la roche encaissante. Cettefracturation et la dilatance qui l’accompagne permettent de propager lachute de pression initiatrice et l’ébullition explosive. L’ébullition explosivede méthane est donc un processus qui potentiellement accompagneet favorise la génèse de mégaséismes en libérant de l’énergie. Afin devalider ce modèle, nous avons étudié la production de méthane par craquagede la matière organique dans des échantillons de carottes de zonesde subduction. Cette analyse montre que (1) la matière organique, bienque présente en faible quantité, est suffisamment abondante pour saturerl’eau dans les pores d’une roche sédimentaire fortement compactée et(2) la caractère sismique/asismique des zones de subduction autour duglobe recouvre, de façon très grossière, une différence entre une « forte »et une « faible » productivité en méthane.

International audience; Here we present the results of the synthesis of three samples of artificial basalts, similar to basalts observed in the crater Gusev on Mars

International audience; Solids irradiated by a 10-20 keV electron beam emit ligth in the UV-visible range, which is called cathodoluminescence (CL). CL imagery is a powerful tool for visualizing minerals and their internal structures (lattice defects, zoning). For example, terrestrial calcite, either of sedimentary or biogenic origin, often display a bright orange CL, as a result of the incorporation of trace Mn2+ in its lattice. Aragonite can also be discriminated from calcite by its green CL. Carbonates are a major target for the search of life on Mars, and CL imagery could contribute to reveal carbonates in situ. Thomas et al. [1] have validated the concept of an electron lamp to make CL imagery of a rock surface placed in a martian CO2 atmosphere. We present 2 examples of terrestrial bacterial microstructures that are revealed by CL. (1) In Sinemurian sediments from the Montmiral borehole (Valence Basin, France), banded wavy calcite in contact with pyrite represents fossilized biofilms of sulfato-reducing bacteria, as confirmed by the sulfur isotopic composition of pyrite ~+36 %0 PDB. (2) At l'Ile Crémieux, north of the Valence basin, a dense filamentous microbial/fungal community with a bright orange CL signature is embedded in vuggy calcite from a tectonic vein. The mat is anchored 1-2 mm deep in the oolitic veinwall and emerges at right angle in the 'open' fracture space. Finally, carbonate vesicles and exhalite crusts from the Svalbard basalt in Groendland, with orange CL, are shown as analogues to carbonates from the martian ALH84001 igneous meteorite. [1]Thomas et al. (2009) in A. Gucsik (Ed.) "Cathodoluminescence and Its Application in the Planetary Sciences"

International audience; Physico-chemical and biological micro-scale environmental parameters within microbial mats formed in hypersaline conditions favour the precipitation of minerals, such as carbonates. We used optical microscopy and the technique "Fluorescence Induction Relaxation " (FIRe) to differentiate the photosynthetic activity of oxygenic photosynthesisers (cyanobacteria) from anoxygenic photosynthesisers (Chloroflexus-like bacteria, CFB) in samples obtained in 2011. After this preliminary investigation, we characterised the elemental composition of the different species of microorganisms, their extracellular substances (EPS), and the minerals precipitated on their surface. This study was made in-situ by µ-PIXE using the nuclear microprobe of the AIFIRA platform (CEN Bordeaux-Gradignan ; protons of 1.5 or 3MeV). With this microprobe it is possible to map the distribution of elements occurring in quantities down to several ppm, a resolution that is particularly favourable for studying microorganisms. SEM observation of the same zones allowed us to localise exactly the microbial structures (cells, EPS) and minerals analysed by nuclear probe. We were thus able to document the differential S and P concentrations in the different microbial species, the CLB being richer in P. Note that the CLB filaments are < 1 µm in diameter. We were also able to demonstrate the anti-correlation of Ca and Mg in the minerals precipitated directly on the microorganisms and on their EPS. Thus we have shown the utility of these in situ, nano-scale methods in studying microbial structures consisting of different species with different metabolic activitie, and different functional groups on their cell walls and EPS implicated in the bioprecipitation of different kinds of minerals. Such features in ancient microbial mats could aid their interpretation and possibly the distinction between ancient oxygenic and anoxygenic mats.

International audience; In order to prepare the next in situ space missions we have created a " lithothèque " of analogue rocks for calibrating and testing future (and existing) space flight instruments. This rock collection is called the International Space Analogue Rockstore (ISAR) and is hosted in the CNRS and the Observatoire des Sciences de l'Univers en Region Centre (OSUC) in Orléans. For maximum science return, all instruments on a single mission should ideally be tested with the same suite of relevant analogue materials. The ISAR lithothéque aims to fulfill this role by providing suitable materials to instrument teams [1]. The lithothèque is accompanied by an online database of all relevant structural, textural, and geochemical data (www.isar.cnrs-orleans.fr).The data base will also be available during missions to aid interpretation of data obtained in situ. Mars is the immediate goal for MSL-2011 and the new international Mars 2018 mission. The lithothèque thus presently contains relevant Mars-analogue rock and mineral samples, a preliminary range of which is now available to the scientific community for instrument testing [2]. The preliminary group of samples covers a range of lithologies to be found on Mars, especially those in Noachain/Hesperian terrains where MSL will land (Gale Crater) and where the 2018 landing site will most likely be located. It includes a variety of basalts (tephrite, primitive basalt, silicified basalt; plus cumulates), komatiites, artificially synthesized martian basalts [3], volcanic sands, a banded iron formation, carbonates associated with volcanic lithologies and hydrothermalism, the clay Nontronite, and hydrothermal cherts. Some of the silicified volcanic sands contain traces of early life that are good analogues for potential martian life [4]. [1] Westall F. et al., LPI contribution 1608, 1346, 42nd LPSC, 2011; [2] Bost N. et al., in review (Icarus); [3] Bost N. et al., in review (Meteoritics); [4] Westall et al., 2011, Planetary and Space Science 59. ISAR Team: N. Bost, F. Westall, C; Ramboz, F. Foucher, D. Pullan, T. Zegers, B. Hoffman, F. Rull, J. Bridges, A; Steele, H. Amundsen, R. Barbieri, A. Hubert, B. Cavalazzi, J. Bridges, M. Viso, J. Vago, S. Petit, A. Meunier, I. Fleischer, G. Klingelhöfer, N. Arndt...

International audience; 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; Basalts are the prevalent rock type on Mars and the products of aqueously altered basalts and hydrated minerals associated with basalts are of particular interest as possible tracers of a past, slightly more clement climate on the planet and/or magmatic processes [1,2]. Study of alteration processes of basalts on Earth that show some similarities to surface and subsurface processes occurring on Mars will help understand and interpret martian features. The Skouriotissa mine in Cyprus is an open pit copper mine (consisting of a very massive sulphide deposit, VMS) exposing the upper pillow basalt formation in the Troodos ophiolitic zone. The basalt has been altered by (1) hydrothermal and deuteritic processes and (2) acidic water (pH

International audience; The ESAR is a collection of well-characterised planetary analogue rocks and minerals that can be used for testing in situ instrumentation for planetary exploration. An online database of all relevant structural, compositional and geotechnics information is also available to the instrument teams and to aid data interpretation during missions.

International audience; There are no suitable terrestrial analogues for martianbasalts, which are richer in Fe and Mg. We present theresults of a preliminary experiment to synthesise martianbasalts based on the Sprit data from Gusev Crater.

International audience; The Orléans-Lithothèque - an analogue rockstore for in situ missions Nicolas Bost, Frances Westall, Claire Ramboz, Axelle Hubert, Derek Pullan, Beda Hofmann, Elisabeth Vergès, Michel Viso, Jorge Vago, Christelle Briois, Bruno Scaillet, Michel Tagger Instruments for in-situ missions to extraterrestrial bodies should ideally be cross calibrated using a common suite of relevant materials. Such multi-instrument calibration would enable a better comparison of instrument performances during the mission, as well as aid in the interpretation of the in-situ measurements. At the CNRS in Orléans, the Observatoire des Sciences de l'Univers de la region Centre is creating a collection of well-characterised rocks that will be available for testing and calibrating instruments to be flown on space missions. The characteristics of the collection's analogue materials will be described in an online database. In view of the upcoming 2018 ExoMars rover mission, we are concentrating initially on materials of direct relevance to Mars. The initial collection includes basalts (ultramafic, weathered, andesitic, hydrothermally-silicified); sediments (volcanic, biolaminated, banded iron formation); and minerals (silica, evaporites, clays, Fe oxides). This set of samples will be augmented with time. All samples will be characterised petrographically, petrologically, and geochemically using the types of analyses likely to be performed during an in-situ mission: hand specimen description, optical microscopy, mineralogical analysis (XRD, Raman and IR spectrometry), elemental analysis (EDX, microprobe, ICP) and organics analysis (Raman, pyr-GCMS).

Symposium B, session 02, paper number B02-0003-10 (Oral); International audience; ExoMars has joined up with the American Max-C rover in a joint, two rover mission to Mars in 2018. The science objectives of ExoMars are to search for traces of past or present life and to document the water/geochemical environment as a function of depth in the shallow subsurface. Max-C seeks to determine the habitability of the surface of Mars with the aim of selecting and caching rocks potentially containing traces of life for the future Mars Sample Return mission. The ExoMars rover will embark a number of scientific instruments to investi-gate rock outcrops and subsurface materials: for observation a variety of cameras and a close up imager, for mineralogy Raman and IR spectrometry as well as an XRD, and GCMS and LDMS for chemical characterisation of the organics. A drill will provide subsurface access to hopefully preserved organics. Max-C will be distinguished by a suite of arm-based tools for observation and mineralogical/elemental mapping. These instruments provide good compara-tive information. In order to optimize the science return of the various instrument suites, it will be useful to test flight instrumentation with the same suite of Mars-analogue rocks. With this objective in mind, a rock library or lithoth'que of rocks that have been fully characterised by standard laboratory instrumentation is being prepared by the Observatoire de l'Univers de la region Centre (OSUC) at Orléans. The ultimate goal is to offer the scientific community a lithoth'que coupled to a database comprising the maximum information on rocks that are analogues of Mars and other planetary bodies. The data base will contain both reference (lab) data and results from experiments using the planetary instruments or models. Here we present a preliminary selection of ten samples for testing the ExoMars instruments. Other samples will become ready as our lithotheque expands. The samples chosen cover a range of lithologies found on Mars -a variety of basalts (plus cumulates), a Late Archaean stromatolitic carbonate (Pongola, South Africa), Early-Mid Archaean shallow-water volcanic sands (Barberton, South Africa; the Pilbara, Australia), an Early Archaean banded iron formation (Pilbara), and a clay (nontronite). The four types of basalts include an ultramafic basalt from Svalbard (Norway) containing dunite xenoliths; an altered basalt from Tenerife (Spain), a primitive basalt from Stromboli (Italy), and silicified altered basalts from Barberton. Apart from their compositional relevance, many of the rocks were formed at a time period equivalent to the Noachian of Mars, and some of them contain fossil (and sometimes recent) biosignatures. These samples have been analysed by optical microscopy, Raman, IR and Müssbauer o

International audience; X-Ray-based analytical methods can be applied in an absolute fashion, provided that matrix effects are calculated and that parameters related to instrumental factors are controlled (Newbury, 1986). When EPMA (Electron Probe Micro Analysis) was conceived at the end of the 60's, this potentiality was abandoned, as the instrument works in a relative fashion, by comparison with standards. At the end of the 70's and in the 80's, PIXE (Proton Induced X-Ray Emission) by contrast was applied in a way that preserved the possibility of an absolute application: the computer programs developed to interpret PIXE spectra calculate matrix effects and also integrate instrumental factors (e.g., Maxwell et al., 1989). In spite of this advantage, and also despite the fact that PIXE application extends to trace element analysis, the development of PIXE in the scientific community was sluggish, in deep contrast with the widespread applications of EPMA. In the field of Earth Sciences particularly, EPMA was recognized by the Mineralogical Society of America to have had 'a revolutionary, profound impact on mineralogy and petrology'. In the same time, PIXE applications remained mainly restricted to trace element analysis, and the potential accuracy of the method was never clearly realized. A first aim of this presentation is to show that, using a simple standardization procedure, the multi-elementary absolute capability of PIXE can be revealed. This in turn changes PIXE into a tool of quantitative mineralogy and trace element geochemistry. We then show that, by coupling PIXE to PIGE (Proton Induced Gamma Ray Emission) and RBS (Rutherford Back Scattering) spectrometries, the Nuclear Microprobe becomes a tool for quantitative mineralogy s.l. and geochemistry, i.e., an instrument to analyze all major to trace elements from Li to U in minerals and their inclusions. In the second part of the presentation, we illustrate the capability of µ-PIXE to analyze in situ individual fluid inclusions that have been carefully localized in space and time. The Hercynian French Massif Central and its sedimentary eastern margin are part of a large European Carbonic Province, which hosts numerous deep CO2 reservoirs and carbonic springs (Blavoux, Dazy, 1990). Carbonic fluids are present at all stages of the long-lived evolution of this crustal segment, from deep metamorphic fluids involved in a thrusting event at 340 M.a to mantle-derived volcanic CO2 related to Neogene volcanism. In order to characterize the main aquo-carbonic fluid reservoirs through time in this crustal segment, we present preliminary data on the trace element content of aquo-carbonic inclusions trapped in the schists at peak and retrograde metamorphic conditions, and compare them to contemporaneous granite-related fluid inclusions

Placer concentrations of rolled chunks of heavy, silvery-white, metallic mineral occur along a rivulet (N25°40.013'; E75°20.851') 15 km east of Jahazpur town of eastern Rajasthan. The float-ore occurs in the Precambrian phyllite that is profusely traversed by vein quartz. Its physical, optical, XRD, EPMA data show that the mineral is native antimony (averaging 97.12%Sb) having ~2% As; minor grains of PbTe are also recognized. Prospecting by the Department of Mines and Geology, Rajasthan has not yet resulted in the discovery of the mother lode. This report describes the mineralogy of the float-ore that has scientific value and is a new occurrence in India.

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 electron-microprobe 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 Cu2+ and Fe3+ and Sn4+ Ge4+ substitution, and leads us to propose a new empirical formula: Cu+8Cu2+2Fe3+3(Fe,Cu)2+ (Sn,Ge)4+(As,Sb)5+S162–. 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.

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.