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Comportement d'éléments formateurs et modificateurs de réseau dans des magmas hydratés

Abstract : This study consists of a better understanding of physical and chemical properties of hydrated magmatic systems associated to subduction zones. We are particularly interested in determining the behavior of network modifiers “trace” elements (Ni and Zr), as well as network formers major elements (Ga and Ge) in this kind of geomaterials. The study is essentially based on an experimental approach, using high-pressure systems (diamond-anvil cell, Paris-Edingurgh press) coupled to X-ray Absorption Fine Structure (XAFS) spectroscopy. For the different chemical systems studied, the results collected under high temperature and/or high pressure show well different behavior for nickel and zirconium as a function of water content. The local structural environment of nickel is highly affected by the presence of water, suggesting a significant interaction between nickel and the aqueous phase. In contrast, the local structure around zirconium is practically unchanged. Moreover, for major analog elements (Ga and Ge), no significant structural modification is observed as a function of temperature, pressure or water content; suggesting possibly that water does not depolymerize the silicate network.
Additional experiments shown the usefulness of XANES (X-ray Absorption Near Edge Structure) spectra for determining, in situ, nickel contents as well as densities of hydrous silicate magmas. Results show a “water/silicate” partitioning coefficient near 0.2; suggesting a low but significant mobilization of nickel by the aqueous phase during the magmatic ascension. Also at around 780 °C / 520 MPa, the apparent-density of hydrated magmas near 1 g/cm3, suggests a structural aspect of “emulsion” type including particularly high water content, as well as a very important dynamic of magmatic ascension in its homogeneous flow regime.
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https://tel.archives-ouvertes.fr/tel-00008421
Contributor : Manuel Munoz <>
Submitted on : Wednesday, February 9, 2005 - 12:16:36 PM
Last modification on : Thursday, January 11, 2018 - 6:19:28 AM
Long-term archiving on: : Friday, September 14, 2012 - 11:05:18 AM

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  • HAL Id : tel-00008421, version 1

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Manuel Munoz. Comportement d'éléments formateurs et modificateurs de réseau dans des magmas hydratés. Géologie appliquée. Université de Marne la Vallée, 2003. Français. ⟨tel-00008421⟩

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