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Antarctic blue ice zones, the most productive locations for meteorite recovery on Earth, contain old ice that is easily accessible and available in large quantities. However, the mechanisms behind these meteorite traps remain a topic of ongoing debate. Here, we propose an interdisciplinary approach to improve our understanding of a meteorite trap in Dronning Maud Land (East Antarctica) on the Nansen blue ice field meteorite trap (2600–3100 m above sea level), where more than half of the Asuka meteorites have been collected. Based on 185 surface blue ice samples, one of the largest observed spatial patterns in oxygen isotopic variation to date is found. Relying on meteorites for which the terrestrial ages are determined using 14C and 36Cl, this surface ice is interpreted to date from the Last Interglacial up to the present-day. By combining state-of-the-art satellite derived surface velocities, surface mass balance modelling and ice flow modelling, we estimate that about 75–85% of the meteorites found on the ice field were supplied by ice flow after entering the ice sheet in an accumulation area of a few hundred square kilometres located south (upstream) of the ice field. Less than 0.4 new meteorites per year are supplied to the ice field through ice flow, suggesting that the hundreds of meteorites found 25 years after the first visit to this ice field mostly represent meteorites that were previously not found, rather than newly supplied meteorites. By combining these findings, the infall rate of meteorites from space is estimated, which is in line with values from the literature, but situated at the higher end of the range. A comparison of the oxygen isotopic variation of the surface blue ice to that of the European Project for Ice Coring in Antarctica (EPICA), Dronning Maud Land (EDML) ice core (located 750 km to the west, at the same elevation), suggests that the regional changes in topography have been relatively limited since the Last Interglacial, supporting theories of an overall stable East Antarctic Ice Sheet (EAIS) over this time period., SCOPUS: ar.j, info:eu-repo/semantics/published

The Siilinjärvi phosphate deposit (Finland) is hosted by an Archean carbonatite complex. The main body is composed of glimmerite, carbonatite and combinations thereof. It is surrounded by a well-developed fenitization zone. Almost all the rocks pertaining to the glimmerite-carbonatite series are considered for exploitation of phosphate. New petrological and in-situ geochemical as well as spectroscopic data obtained by cathodoluminescence, Raman and laser-induced breakdown spectroscopy make it possible to constrain the genesis and evolution of apatite through time. Apatite in the glimmerite-carbonatite series formed by igneous processes. An increase in rare earth elements (REE) content during apatite deposition can be explained by re-equilibration of early apatite (via sub-solidus diffusion at the magmatic stage) with a fresh carbonatitic magma enriched in these elements. This late carbonatite emplacement has been known as a major contributor to the overall P and REE endowment of the system and is likely connected to fenitization and alkali-rich fluids. These fluids - enriched in REE - would have interacted with apatite in the fenite, resulting in an increase in REE content through coupled dissolution–reprecipitation processes. Finally, a marked decrease in LREE is observed in apatite hosted by fenite. It highlights the alteration of apatite by a REE-poor fluid during a late-magmatic/hydrothermal stage. Regarding the potential for REE exploitation, geochemical data combined with an estimation of the reserves indicate a sub-economic potential of REE to be exploited as by-products of phosphate mining. Spectroscopic analyses further provide helpful data for exploration, by determining the P and REE distribution and the enrichment in carbonatite and within apatite., SCOPUS: ar.j, info:eu-repo/semantics/published

Ultramafic hosted hydrothermal deposits are ubiquitous along slow-spreading ridges such as the Mid-Atlantic Ridge (MAR; e.g. Ashadzé Rainbow, Lost City) where they exert a major control on the cycling of economically important elements (e.g. Zn, Cu, Ni). However, the origin of metal mobility in these environments remains unclear. Here we use Zn (δ66Zn), Cu (δ65Cu) and Fe (δ56Fe) stable isotopes to explore the mobility of metals during (1) the serpentinization of the Rainbow massif basement in a seawater dominated system at low temperature (350 °C) mineralization of serpentinites through seawater-derived fluids that interacted with gabbro prior to interacting with serpentinite near hydrothermal sites (stockworks). The Rainbow samples display among the largest range of isotopic variations ever reported for ultramafic rocks (−0.10‰ ≤ δ66Zn ≤ +0.47‰; −0.93‰ ≤ δ65Cu ≤ +0.24‰; −0.15‰ ≤ δ56Fe ≤ +0.25‰). These variations reflect a two-stage process. (1) Serpentinization of the ultramafic basement is accompanied by a decrease in Zn (26–41 ppm) and Cu (1–13 ppm) concentrations and an increase of δ66Zn (+0.30–+0.47‰) in peridotites relative to primitive mantle (Zn ∼ 55 ppm, Cu ∼ 20 ppm, δ66Zn ∼ +0.16‰). Striking correlations between δ66Zn and indices of serpentinization (LOI and Fe/3+ΣFe) show preferential leaching of isotopically light Zn by fluids during the serpentinization of the massif. This isotopic fractionation is controlled by the dissolution of both mantle sulfides and/or spinels and Zn complexation with chlorine in fluids. At this stage, Fe seems to be immobile as attested by correlations between δ56Fe and indices of peridotite fertility (e.g. Al2O3/SiO2). (2) The mineralization of serpentinites near the Rainbow stockwork is accompanied by an increase in Fe/3+ΣFe (>0.7), FeO (up to 19.8 wt%), Zn (≫50 ppm) and Cu (≫20 ppm) concentrations. The δ66Zn and δ65Cu values progressively decrease with indices of serpentinite mineralization (e.g. Zn, Cu, Fe/3+ΣFe), while several samples display abnormally high δ56Fe (up to 0.25‰) relative to primitive mantle (δ56Fe ∼ 0.025‰), suggesting a high mobility of Zn, Cu and Fe in high temperature hydrothermal fluids. These isotopic fractionations can be explained by the local oxidation of sulfur bearing fluids in contact with seawater. This process enhances metal precipitation as well as the formation of Fe3+-bearing phases, such as magnetite, beneath the stockwork, explaining the presence of magnetic anomalies below the Rainbow hydrothermal field. Our study shows that the mobility of metals in hydrothermal fluids can be enhanced by both peridotite interaction with seawater or with fluid that interacted with deeper mafic bodies and then flowed to the surface. These processes may generate hydrothermal deposits with distinct metal signatures., SCOPUS: ar.j, info:eu-repo/semantics/published

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Si les différents travaux réalisés dans une forge sont assez bien connus, il est difficile de les retrouver au travers de l’analyse des seuls déchets. Ce sont pourtant ceux-ci que l’on retrouve presque exclusivement sur les ateliers dégagés au cours de fouilles archéologiques. Pour en extraire un maximum de renseignements, il est nécessaire de mettre en place une méthodologie rigoureuse d’étude, depuis l’échantillonnage sur le terrain jusqu’aux analyses chimiques en laboratoire. Les notions de quantification et de représentativité sont extrêmement importantes pour tenter de qualifier et quantifier les travaux effectués par le forgeron, pour déterminer la nature des matériaux employés et pour tenter d’estimer une quantité minimale de fer travaillé. L’étude, bien que ciblée sur les scories en culot, montre que l’ensemble des déchets produits dans un atelier doit être pris en considération lors des études paléométallurgiques si l’on veut réellement appréhender l’atelier. L’exemple du site du Puy-de-Grâce (La Tène finale) permet de documenter les apports de cette méthodologie. If the different works produced in a smithing workshop are well known, it is difficult to identify them only from the analyses from the wastes. However, these wastes are generally the only remnants that can be found during excavation of archaeological ironworkshops. To obtain the maximum of informations of these wastes, it is necessary to propose a rigorous methodology, from the sampling in the archaeological site to chemical analyses in laboratory. The quantification and representativeness notions are very important to qualify and quantify the works operated by the blacksmith, to determine the nature of used materials and to estimate the minimal quantity of worked iron. This study, although targeted on the tape slags, shows that it is necessary to take into account the totality of the wastes found in the archaeological smithy during the archeaometallurgical studies for a good comprehension of this smithy functioning. The Puy-de-Grâce example (France) allows documenting the contribution of this methodology.

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The deformation of two granitic massifs along a dextral wrench fault zone (the South Armorican Shear Zone) is examined at the sample and grain scales. We note that an association of continuous-discontinuous deformation mechanisms is responsible for the mylonitisation at the grain scale. The general characteristics of the deformation (strain, ellipsoid type, strain regime, non-coaxial model) and quartz fabrics measured in these mylonites at each of the mylonitisation stages described, are also discussed.

In spite of the presence of minerals containing antimony, tin, arsenic, nickel and cobalt, the veins BGPC occurring in Western Brittany belong to a classic para-genetic type called « formation du plomb argentifère »., Malgré la présence de minéraux d'antimoine, d'étain, d'arsenic, de nickel et de cobalt, les filons BGPC de Bretagne occidentale appartiennent typiquement à la classique « formation du plomb argentifère »., Chauris Louis, Laforêt Claude, Picot Paul, Pierrot Roland. Individualité paragénétique de la formation filonienne BGPC en Bretagne occidentale. Aperçu préliminaire. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 99, 5, 1976. pp. 287-293.

Le granite de Ploumanac'h présente près de La Clarté des accidents pegmatitiques à allanite et molybdénite. La pegmatite à allanite est caractérisée par l'abondance des minéraux mélanocrates ; elle paraît devoir être classée parmi les pegmatites de la «série hybride » ; elle correspond aux phases B et C de la classification de Fersman., Chauris Louis. Pegmatites à allanite et molybdénite dans le granite de Ploumanac'h (Côtes-du-Nord). In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 81, 4-6, 1958. pp. 150-153.

Near the Locronan, Scaër and Saint-Renan granites (Finistère), bulk concentrations of aluminosilicates outcrop : kyanite or andalusite in quartz-sericite schists ; kyanite and andalusite in staurolite bearing micaschists ; sillimanite in biotite gneiss. Notes about the possible part in the nodular concentrations genesis of the pneumatolytic processes bound to those granites., A proximité des granites de Locronan, de Scaër et de Saint-Renan (Finistère), apparaissent des concentrations massives en silicates d'alumine : disthène ou andalousite dans des schistes quartzo˗sériciteux ; disthène et andalousite dans des micaschistes à staurotide ; sillimanite dans des gneiss à biotite. Remarques sur le rôle éventuel des processus pneumatolytiques liés à ces granites dans la genèse des concentrations nodulaires., Barrière Michel, Chauris Louis, Le Bail François. Nodules de silicates d'alumine autour de granites en Bretagne occidentale. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 96, 2, 1973. pp. 150-154.

Interpreting the kaolin formations of the Massif Amorcain can be tricky because the presence of kaolinite does not have much geological significance. An examination of the differential thermal analysis curves does not make it possible to distinguish between the different kaolins under study. Our simple X-ray system will not permit a precise determination to be made of the different minerals in the kaolinite group. Electron microscope studies of kaolins have shown that there is a close correlation between the various recognized morphological types and their geological history. These results have made it possible to clarify to some extent the history of the numerous tertiary formations in Brittany. A study, by way of example, of the Rouge complex (Loire-Atlantique Department) and of two basins located south of Rennes demonstrates the value of this investigation technique.", L'interprétation des formations kaoliniques du Massif Armoricain est parfois délicate car la présence de la kaolinite n'a pas une grande signification géologique. L'examen des courbes d'analyse thermique différentielle ne permet pas de faire de distinction entre les différents kaolins étudiés. La simplicité de notre montage de rayons X ne rend pas possible la détermination précise des différents minéraux du groupe de la kaolinite. L'étude des kaolins en microscopie électronique a montré qu'il existait une corrélation étroite entre les divers types morphologiques reconnus et leur histoire géologique. Ces résultats ont permis d'apporter des précisions sur l'histoire de nombreuses formations tertiaires de Bretagne. L'étude à titre d'exemple, de deux bassins situés au Sud de Rennes et du complexe de Rougé (Loire-Atlantique) montrent l'intérêt de cette technique d'étude., Estéoule-Choux Janine. Intérêt de l'étude morphologique des kaolins en géologie. In: Bulletin du Groupe français des argiles. Tome 16, nouvelle série n°11, 1965. pp. 25-35.

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The small lead-antimony deposit of Bestrée (Finistère) is the best French occurrence of fiilôppite. There are three different periods of deposition : the first with stibnite, the second with zinkenite, sphalerite and sulphosalts of the plagionite group, the last with jamesonite, framboïdal pyrite and very antimoniferous galena. The succession from stibnite to galena and its telescoping on a small scale are very remarkable., Le petit indice à antimoine et plomb de Bestrée (Finistère) constitue la meilleure occurrence française de fiilôppite. Trois phases s'y succèdent : la première à stibine, la seconde à zinkénite, blende et sulfosels du groupe de la plagionite, la troisième à jamesonite, pyrite framboïdale et galène fortement antimonifère. L'évolution de la succession de la stibine à la galène et son télescopage à échelle réduite représentent un phénomène très rare., Moëlo Yves, Fouquet Yves, Laforêt Claude, Chauris Louis. L'indice plombo-antimonifère de Bestrée (cap Sizun, Finistère). In: Bulletin de Minéralogie, volume 101, 3, 1978. pp. 363-367.

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The south-arm orican leucogranites are progressively deformed in a major dextral hercy-nian shear. The quartz fabric is shown at different stages of the strain history defined by the spatial evolution of the planar structures at microtectonic scale. Non coaxial deformation occurs and progressive rotation of c axis orientations is demonstrated. The influence of heterogeneities on this evolution is briefly discussed., Les leucogranites sud-armoricains sont progressivement orthogneissifiésle long d'un cisaillement dextre hercynien. Les orientations préférentielles du quartz sont mesurées à divers stades de l'évolution de la déformation, définie à l'échelle microtectonique par l'évolution spatiale des structures planaires. Dans le régime de déformation non coaxiale envisagé, on met en évidence une rotation progressive de la fabrique et on discute brièvement l'influence des hétérogénéités sur l'évolution des orientations préférentielles des axes c du quartz., Berthé Didier, Choukroune Pierre, Gapais Denis. Orientations préférentielles du quartz et orthogneissification progressive en régime cisaillant : l'exemple du cisaillement sud-armoricain. In: Bulletin de Minéralogie, volume 102, 2-3, 1979. Mécanismes de déformation des minéraux et des roches.

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