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Développements chimiques et instrumentaux en géochimie, en vue des analyses isotopiques Lu-Hf et Sm-Nd. Application à la géochronologie des roches métamorphiques de haute pression.

Abstract : This work presents a set of four distinct parts, which are related to the geochemical analysis. The first part is focused on the isotope dilution method and its applications, and is build as a group of published articles. The isotope dilution theory is exposed, and the advantages inherent to this primary method are discussed. The powerfull combination of isotope dilution with matrix-elements removal for obtaining high-quality analysis is assessed for geological samples. The second part is devoted to the chemical separation of Lanthanides and Hf from matrix in geological samples, in view of the isotopic analysis of the Sm﷓Nd and Lu﷓Hf radioactive decay systems. Three new methods are described, assessed and compared ones with others. The analytical protocols for the MC﷓ICP﷓MS measurements are detailed, and some analytical pitfalls are highlighted. For each, a solution avoiding the generated errors is proposed. The third part describes some introduction lines for plasma-source instruments. These devices are based essentially on desolvatation systems and micro-nebuliser developments. An example of application with a MC﷓ICP﷓MS is showed and commented. The fourth and last part is dedicated to geological applications of the previously assessed methods. The processed samples are high-grade metamorphic rocks from the European and North-African Hercynian belt (massive granulites from the Bohemian Massif (Austria, poland), granulitic xenolites from Morocco), and eclogitized rocks from the Sesia zone (Franco-Italian Alps). We obtained interesting data, implicating that, probably, geochronometers are, in crustally derived rocks, very sensitive to the previous history of the rock-constituting materials. We suppose that the behavior of elements involved in the studied geochronometers are more complex than generally admitted.
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Contributor : Brieuc Le Fevre <>
Submitted on : Tuesday, October 14, 2003 - 3:43:05 PM
Last modification on : Wednesday, November 20, 2019 - 3:21:55 AM
Long-term archiving on: : Friday, April 2, 2010 - 7:40:24 PM

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  • HAL Id : tel-00003563, version 1

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Brieuc Le Fèvre. Développements chimiques et instrumentaux en géochimie, en vue des analyses isotopiques Lu-Hf et Sm-Nd. Application à la géochronologie des roches métamorphiques de haute pression.. Autre. Université Blaise Pascal - Clermont-Ferrand II, 2002. Français. ⟨tel-00003563⟩

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