Cosmochimie isotopique du molybdène

Abstract : The solar system represents the end-product of a complex and slow maturation of matter. The molybdenum isotopie composition measured in extraterrestrial samples bears information on the events that contributed to shaping the solar system we live in. (i) No mass fractionation is observed in primitive or differentiated meteorites. (ii) No evidence for the presence of live 97Tc in the nascent solar system is found (97Tcf98Ru < 4 x w-4). This result is consistent with the low 97Tc abundance expected from production of extinct p-radionuclides in type II supernovae and chemical evolution of the Galaxy incorporating infall and non-linearity. (iii) Inherited nucleosynthetic anomalies are observed in both differentiated meteorites and leachate fractions of primitive chondrites. Thus, two nucieosynthetic poles are identified. The Mo-rn spectrum is hosted by circumstellar carbide grains and is characterized by an enrichment in s-nuclides while the Mo-w spectrum represents the ambient isotopie signature of the nebula and is characterized by a deficit in s-nuclides. The presence of molybdenum nucleosynthetic anomalies at macroscopic scale is then used in order to discuss the genetic relationships between planetary bodies and investigate the spatial distribution of circumstellar dust in the nebula.
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Nicolas Dauphas. Cosmochimie isotopique du molybdène. Sciences de la Terre. Institut National Polytechnique de Lorraine, 2002. Français. ⟨NNT : 2002INPL006N⟩. ⟨tel-01749721⟩

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