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| Registros recuperados: 13 | |
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| Etoubleau, Joel; Bohn, Marcel; Fouquet, Yves; Cambon, Pierre; Le Suave, Raymond. |
| A range of X-ray analytical techniques contributes particularly well to the mineralogical and geochemical characterisations of cobalt-rich iron and manganese oxides crusts. X-ray diffraction is used to identify the weak crystallinity of the material. Bulk geochemical characterisation of the crusts is done by X-ray fluorescence for the precise determination of ca. thirty major and trace elements. Fine scale analysis is carried out by electron microprobe to quantitatively map the distribution of elements in oxide phases within the crusts. Microprobe work is essential to obtain the chemical composition of the embedded metallic micro-meteorites. |
| Tipo: Text |
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| Ano: 2000 |
URL: http://archimer.ifremer.fr/doc/00000/10415/9517.pdf |
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| Chu, N; Johnson, C; Beard, B; German, C; Nesbitt, R; Frank, M; Bohn, Marcel; Kubik, P; Usui, A; Graham, I. |
| Temporal variations in Fe isotope compositions at three locations in the Pacific Ocean over the last 10 Ma are inferred from high-resolution analyses of three hydrogenetic ferromanganese crusts. Iron pathways to the central deep Pacific Ocean appear to have remained constant over the past 10 Ma, reflected by a remarkably constant Fe isotope composition, despite large changes in the Fe delivery rates to the surface ocean via dust. These results suggest that the Fe cycle in the deep ocean is decoupled from that in surface waters. By contrast, one ferromanganese crust from the Izu-Bonin (IB) back-arc/marginal basin of the W. Pacific exhibits large delta Fe-56 variations. In that crust, decreases in delta Fe-56 values correlate with increases in Mn, Mg, Ni,... |
| Tipo: Text |
Palavras-chave: Pacific Ocean; Izu Bonin; Hydrothen nal; Ferromanganese crusts; Fe isotopes. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-3700.pdf |
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| Beck, Pierre; Chaussidon, M; Barrat, J.a.; Gillet, Ph.; Bohn, Marcel. |
| Ion-microprobe was used to measure Li abundances and isotopic compositions in pyroxenes from three Martian meteorites belonging to the nakhlite family. The profiles performed across augite crystals from Northwest Africa 817 show a large isotopic zoning from crystal cores (delta Li-7 similar to 0 parts per thousand) to rims (delta Li-7 similar to +20 parts per thousand) while Li abundances are almost constant (similar to 9.2 mu g/g). Unlike NWA 817, the pyroxene studied in the Miller Range 03346 nakhlite shows a zoning in Li abundance, with concentrations increasing from similar to 2.5 mu g/g in the core to similar to 9 mu g/ g in the rim. The augite rim (delta Li-7 = +7 parts per thousand) is slightly enriched in Li-7 with regard to the core (delta Li-7 =... |
| Tipo: Text |
Palavras-chave: Magma; Pyroxene; Lithium; Geochemistry; Mars planet; Isotopic composition. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1955.pdf |
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| Laverne, Christine; Grauby, Olivier; Alt, Jeffrey C.; Bohn, Marcel. |
| Hydroschorlomite, a Ti-, Ca-, Fe-rich andraditic garnet present in the deepest cores of basalts (661-749 mbsf) drilled in Hole 1256D during Ocean Drilling Program (ODP) Leg 206 (equatorial east Pacific), is reported here for the first time in oceanic crust. Detailed petrological and mineralogical studies by optical microscope, electron microprobe, scanning and transmission electron microscope, and micro-Raman spectroscopy are used to characterize this hydrogarnet and its relationships with other minerals. Hydroschorlomite occurs in Hole 1256D as small (5-50 mu m) anhedral or euhedral crystals associated either with celadonite in black halos adjacent to celadonite veins or with brown saponitic phyllosilicate in brown alteration halos adjacent to veins of... |
| Tipo: Text |
Palavras-chave: Mineralogy and petrology : alteration and weathering processes; Mineralogy and petrology : hydrothermal systems; Hydrogarnet; Titanium; Alteration halo; Low temperature alteration; Oceanic basalt. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-2093.pdf |
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| Vlastelic, Ivan; Dosso, Laure; Bougault, Henri; Aslanian, Daniel; Geli, Louis; Etoubleau, Joel; Bohn, Marcel; Joron, Jl; Bollinger, C. |
| Axial bathymetry, major/trace elements, and isotopes suggest:that the Pacific-Antarctic Ridge (PAR) between 56 degrees S and 66 degrees S is devoid of any hotspot influence. PAR (56-66 degrees 5) samples have in-average lower Sr-87/Sr-86 and Nd-143/Nd-144 and higher Pb-206/(204)pb than northern Pacific midocean ridge basalts (MORB), and also than MORE from the other oceans. The high variability of Pb isotopic ratios (compared to Sr and Nd) can be due to either a;general high mu (HIMU) (high U/Pb) affinity of the southern Pacific upper mantle or to a mantle event first recorded in time by Pb isotopes. Compiling the results of this study with those from the PAR between 53 degrees S and 57 degrees S gives a continuous view of mantle characteristics from south... |
| Tipo: Text |
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| Ano: 2000 |
URL: https://archimer.ifremer.fr/doc/00000/10578/9396.pdf |
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| Lauter, Lukas; Hochenauer, Roman; Buchegger, Christoph; Bohn, Marcel; Lengauer, Walter. |
| The solubilities of the most common grain -growth inhibitors (GGIs) Cr, V, Ta, Mo, Nb, Zr and certain combinations there of in the binder phase of WC-Co hardmetals as well as hardmetals of the type WCTiC-TiN-TaC-NbC-Co containing an fcc MC carbide (or carbonitride) phase "MC"("WC-MC-Co" hardmetals) were analysed by means of WDS-EPMA. The carbon potential of the binder phase was fixed at its highest and lowest maxima by the presence of either graphite or eta (M6C) phases. In case of low-carbon hardmetals the composition of M6C, and in the MC-containing hardmetals the composition of the MC phase, was analysed. Two types of solubilities were determined. The first type was measured after controlled cool-down from liquid-phase sintering temperature and... |
| Tipo: Text |
Palavras-chave: Hardmetal; Cemented carbides; Grain-growth inhibitor; Nitrogen; Binder phase; Solubility; EPMA. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00332/44332/44155.pdf |
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| Clement, Jean-philippe; Caroff, Martial; Dudoignon, Patrick; Launeau, Patrick; Bohn, Marcel; Cotten, Joseph; Blais, Sylvain; Guille, Gérard. |
| This paper reports new field observations and new petrological, textural and geochemical data on two gabbroic intrusions and one pegmatoid dyke from the French Polynesian islands Maupiti and Bora Bora, respectively. Olivine crystals from the Faataufi and Barque de Hiro gabbros (Maupiti) include High Temperature Iddingsite (HTI), exhibiting three distinct morphological facies. Chemical and crystallographical data performed by electron microprobe, scanning microscope, X-ray diffractometry and Near InfraRed spectroscopy show that HTI results from modifications of olivine structure through intense hydroxylation and Fe-oxidation. The HTI-free 120 m-wide Cloche de Hiro dyke (Bora Bora) exhibits a textural zonation from heterogranular/intergranular gabbro... |
| Tipo: Text |
Palavras-chave: Society Islands; French Polynesia; Pegmatoid; Vapor differentiation; Olivine; Gabbros. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2999.pdf |
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| Beck, Pierre; Barrat, J; Chaussidon, M; Gillet, P; Bohn, Marcel. |
| Lithium abundances and isotopic compositions were measured by ion microprobe in individual grains of pyroxene, and in a few maskelynites and Ca-phosphates grains, from the Martian meteorite Northwest Africa 480 (NWA 480). In pyroxenes Li abundances are nearly constant from core to rim with concentrations ranging between 3 and 4 mug/g. In contrast, a significant isotopic zoning is observed with delta(7)Li values increasing within single crystals from similar to -17parts per thousand in the core to similar to +10parts per thousand in the rim, most of the variability being observed in the core. Plagioclase (now maskelynite) and phosphate crystals, which co-crystallized with the pyroxene rims, display similar delta(7) Li values. Because of the incompatible... |
| Tipo: Text |
Palavras-chave: Mars planet; Magma; Pyroxene; Isotopic composition; Lithium; Geochemistry. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-735.pdf |
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| Gillet, P; Barrat, J; Beck, P; Marty, B; Greenwood, R; Franchi, I; Bohn, Marcel; Cotten, J. |
| Northwest Africa (NWA) 1950 is a new member of the lherzolitic shergottite clan of the Martian meteorites recently found in the Atlas Mountains. The petrological, mineralogical, and geochemical data are very close to those of the other known lherzolitic shergottites. The meteorite has a cumulate gabbroic texture and its mineralogy consists of olivine (FO66 to FO75), low and high-Ca pyroxenes (En(78)Fs(19)Wo(2)-En(60)FS(26)W(14); En(53)Fs(16)Wo(31)-En(45)Fs(14)Wo(41)), and plagioclase (An(57)Ab(41)Or(1) to An(40)Ab(57)Or(3); entirely converted into maskelynite during intense shock metamorphism). Accessory minerals include phosphates (merrillite), chromite and spinels, sulfides, and a glass rich in potassium. The oxygen isotopic values lie on the fractional... |
| Tipo: Text |
Palavras-chave: Meteorites; Atlas Mountains; Shergottite; Lherzolitic. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-900.pdf |
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| Bayon, Germain; Henderson, G. M.; Bohn, Marcel. |
| On continental margins, oxidation of methane-rich fluids from the sediment often leads to formation of authigenic carbonate pavements on the seafloor. The biogeochemical processes involved during this carbonate precipitation are increasingly understood, but little is known about the duration or mode of carbonate crust formation. Here, we report uranium and thorium concentrations and isotope compositions for a set of 14 samples drilled across an authigenic carbonate pavement, which provide the first stratigraphy for a cold-seep carbonate crust. The 5.5-cm thick crust (NL7-CC2) was collected by Submersible on the Nile deep-sea fan in an area of active fluid venting. U-Th analyses must be corrected for initial Th and measurement of co-existing sediments... |
| Tipo: Text |
Palavras-chave: Nile fan; Cold seeps; Authigenic carbonates; U series. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6450.pdf |
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| Dias, M.; Carvalho, P. A.; Dias, A. P.; Bohn, Marcel; Franco, N.; Tougait, O.; Noel, H.; Goncalves, A. P.. |
| The solidification paths for UFeB4, UFe3B2 and UFe4B, ternary compounds, situated along the U:(Fe,B) = 1:5 line in the B-Fe-U phase diagram, are proposed based on x-ray powder diffraction measurements, differential thermal analysis, heating curves and scanning electron microscopy observations complemented with energy and wavelength dispersive x-ray spectroscopies. The compounds melt incongruently and are formed by peritectic reactions. The present work demonstrates the existence of a cascade of peritectic reactions along the U:(Fe,B) = 1:5 composition line, establishes peritectic temperatures and proposes an isopleth diagram along this line. |
| Tipo: Text |
Palavras-chave: Microstructure; Phase transformations; Ternary alloy system. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00002/11369/8168.pdf |
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| Registros recuperados: 13 | |
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