Datation à haute précision par l'26Al de l'histoire du disque d'accrétion

Abstract : The disk history is a very interesting period of the early Solar System history, i.e. the period during which occurred most of the processes leading from the mixing of nebular gas and dust to grains, and then planetesimals, which will then constitute the starting material for formation of planetary embryos and terrestrial planets. The witnesses of this period that we have in the laboratory are the chondrite constituents, mostly refractory inclusions (CAIs) and chondrules. One of the central questions regarding the processes leading to the formation of CAIs and chondrules is the timing. Villeneuve et al. (2009, 2011) have shown that 26Al and Mg isotopes were homogeneously distributed in the accretion disk, at a level allowing the use of the 26Al-26Mg system as the most precise short-lived chronometer to constrain the 2 or 3 first million years of the disk history. My PhD project aimed at reconsidering the 26Al study with more precise measurements, and by combining in-situ (by MC-SIMS) and bulk (by HR-MC-ICPMS) analyses. The analytical developments we set for Mg-isotope measurements (because of the high precision needed) were then applied to a set of extraterrestrial materials, including Mg-rich isolated olivines and Mg-rich olivines in porphyritic type I chondrules from the Allende CV3 meteorite, as well as chondrules from the same meteorite, and olivines from the Eagle Station pallasite. The whole data set allowed to answer questions such as (i) the origin of chondrule precursor materials and the time of chondrule formation, as well as (ii) the origin of Mg-rich refractory olivines, and the possibility that the latters were part of chondrule precursors
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Tu-Han Luu. Datation à haute précision par l'26Al de l'histoire du disque d'accrétion. Autre. Université de Lorraine, 2013. Français. ⟨NNT : 2013LORR0225⟩. ⟨tel-01750520⟩

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