Jean Dubessy

Bio: Jean Dubessy is an academic researcher from Nancy-Université. The author has contributed to research in topics: Fluid inclusions & Raman spectroscopy. The author has an hindex of 42, co-authored 86 publications receiving 4246 citations. Previous affiliations of Jean Dubessy include Carnegie Institution for Science & University of Lorraine.

Advances in C-O-H-N-S fluid geochemistry based on micro-Raman spectrometric analysis of fluid inclusions

Abstract: The first part of this paper focuses on the analysis of fluid inclusions by micro-Raman spectrometry . S042and HSare the only polyatomic anions identified by this technique . Na+ , Ca2+ , Mg2+ , Fe2+ cations can be identified by the Raman spectrum of the corresponding salt hydrate which nucleates on cooling. Gas analysis is the most fruitful field of application of micro-Raman spectrometry . Errors in the reconstruction of the bulk V-X properties of gas-bearing fluid inclusions, arising either from Raman analysis or from the quantitative interpretation of phase equilibria, are discussed. Geochemical constraints inferred from these analyses are considered in the second part. The V-X properties of fluids in the C-O-H-N-S system are deduced mainly from room-temperature measurements . They are shown to be representative of the fluid V-X properties in the P-T conditions of trapping, and thus, to y ield representative f02 and fS2 . The paleo-redox state of fluids associated with U, Sn, W, and Au deposits is shown partly to account for the contrasted behaviour of these metals at the hydrothermal stage . Gas concentration is a key parameter for control­ ling meta I transport and deposition properties of fluids. This is because it controls the static dielectric constant of the fluid, wh ich in turns constrains the ion-pair stability . It is shown that some Nrbearing fluids may be the end product of major redox reactions . Finally , the H2and 02-bearing fluid inclusions found in three uranium deposits provide evidence for water radiolysis by alpha particles. Key-words: fluid inclusions, micro-Raman analysis, C-O-H-N-S system, chemical equilibrium, Sn-W-U-Au-deposit.

Fluid composition and evolution in coesite-bearing rocks (Dora-Maira massif, Western Alps): implications for element recycling during subduction

Abstract: Fluid inclusions and F, Cl concentration of hydrous minerals were analysed in the coesite-pyrope quartzite, the interlayered jadeite quartzite and their country-rock gneiss from the Dora-Maira massif using a combination of microthermometry, Raman spectrometry, synchrotron X-ray microfiuorescence and electron microprobe analysis. Three populations of fluid inclusions were recognized texturally and can be related to distinct metamorphic stages. A low-salinity aqueous fluid occurs in the retrogressed country gneiss and as late secondary inclusions in jadeite quartzite and chloritized pyrope. An earlier secondary population is found in matrix quartz of the jadeite- and pyro-pe-quartzites. This population can be related to the early decompression and so to incipient breakdown of garnet into phlogopite-bearing assemblages. The inclusion fluid is highly saline (up to 84 wt% equivalent NaCl) and contains Na, Ca, Fe, Cu and Zn as major cations. In pyrope quartzite, additional K was found in these brines, which locally coexist with CO2-rich inclusions. The oldest fluid inclusions are preserved in kyanite grains included in fresh pyrope and in pyrope itself. In pyrope, all inclusions have decrepitated and contain magnesite, an Mg-phosphate, sheet-silicate(s), a chloride and an opaque phase, with no fluid preser ved. In contrast, the kyanite inclusions in pyrope preserve primary H2O-CO2 low-salinity fluid inclusions, probably owing to the low compressibility of the kyanite inclusions and host garnet. In spite of in-situ re-equilibration, these inclusions can be interpreted as relics of the dehydration fluid that attended pyrope growth. These correlations between textural and chemical fluid inclusion data and metamorphic stages are consistent with the fluid composition calculated from the halogen content of different generations of phlogopite and biotite. The preservation of different fluid compositions, both in time and space, is evidence for local control and possibly origin of the fluids, in agreement with isotopic data. These results, in particular the absence of CO2 in the jadeite quartzite, are best interpreted in terms of a fluid-melt system evolution. With increasing metamorphism, partitioning of H2O, Na, Ca, Fe and heavy metals into melt (jadeite quartzite) and Mg, Na/K, F, CO2 and P(?) into a residual aqueous fluid can account for depletion in Na, Ca and Fe of the pyrope quartzite. During the retrograde path, a H 2 O rose as melt crystallized, generating the two populations of hypersaline and water-rich fluids that were highly reactive to pyrope. The process of fluid-melt interaction envisioned here coupled with models of melt extraction in subduction zones provides an attractive opportunity for the instantaneous ( < 1 Ma) and selective transport of elements between a downgoing slab and the overlying mantle wedge.

Chemical thermodynamics of uranium

Abstract: I. Introduction. Background. Focus of the review. Review procedure and results. The NEA-TDB data base system. Presentation of the selected data. II. Standards and Conventions. Symbols, terminology and nomenclature. Units and conversion factors. Standard and reference conditions. Fundamental physical constants. III. Selected Uranium Data. IV. Selected Auxiliary Data. V. Discussion of Data Selection. Elemental uranium. Aqua ions. Oxide, hydride and hydroxide species. VI. Discussion of Auxiliary Data Selection. Reference list. Authors list. Formula list. Discussion of selected references. Ionic strength corrections. Assigned uncertainties. The estimation of entropies.

Laser-induced breakdown spectroscopy (LIBS), part II: review of instrumental and methodological approaches to material analysis and applications to different fields.

Abstract: The first part of this two-part review focused on the fundamental and diagnostics aspects of laser-induced plasmas, only touching briefly upon concepts such as sensitivity and detection limits and largely omitting any discussion of the vast panorama of the practical applications of the technique. Clearly a true LIBS community has emerged, which promises to quicken the pace of LIBS developments, applications, and implementations. With this second part, a more applied flavor is taken, and its intended goal is summarizing the current state-of-the-art of analytical LIBS, providing a contemporary snapshot of LIBS applications, and highlighting new directions in laser-induced breakdown spectroscopy, such as novel approaches, instrumental developments, and advanced use of chemometric tools. More specifically, we discuss instrumental and analytical approaches (e.g., double- and multi-pulse LIBS to improve the sensitivity), calibration-free approaches, hyphenated approaches in which techniques such as Raman and fluorescence are coupled with LIBS to increase sensitivity and information power, resonantly enhanced LIBS approaches, signal processing and optimization (e.g., signal-to-noise analysis), and finally applications. An attempt is made to provide an updated view of the role played by LIBS in the various fields, with emphasis on applications considered to be unique. We finally try to assess where LIBS is going as an analytical field, where in our opinion it should go, and what should still be done for consolidating the technique as a mature method of chemical analysis.