CONICET | Buscador de Institutos y Recursos Humanos

AbstractThe process/es involved in chondrule formation cover a wide range of mechanisms whose nature is still unknown. Ourattention is focused on solar nebula processes mainly in untangling the origin of the initial liquid droplets that turn into chondrules. To do this, we start deciphering the processes under which the chondritic constituents of glass-rich, PO and POP chondrules from the Unequilibrated Ordinary Chondrite (UOC) Tieschitz L/H3.6 could have been formed. One constituent is theinitial refractory liquid. This chilled liquid, presented as primary glass inclusions in olivine or as glass mesostasis, has traceelement abundances with unfractionated patterns and lacks the chemical signature that is expected from a geochemical(liquid-crystal) fractionation. The unfractionated crystal-liquid distribution coefficients observed in the glass-rich, PO andPOP chondrules indicate that formation of these objects was not dominated by an igneous process. In addition, the good correlation of elements with different geochemical and cosmochemical properties (e.g., Yb and La-Ce) that spread around theprimordial ratio, indicate that a cosmochemical (condensation) instead of a geochemical process may have been involvedin the origin of this refractory liquid. We end up discussing a secondary process: the alkali-Ca exchange reaction that couldhave taken place within a cooling nebula at sub-solidus temperatures. The extent to which these solid/gas exchange reactionstook place will determine the final composition of the chondrules.