Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules

International audienceIsotopic anomalies in chondruleshold important clues about the dynamics of mixing and transport processes in the solar accretion disk. The meaning oftheseanomaliesis debated, however, andtheyhavebeeninterpreted to indicateeither disk-wide transport of chondrules orlocal heterogeneitiesof chondrule precursors.Amajor shortcoming of previous studiesis that they all relied on isotopic data for a single element (either Cr, Ti, or O), which does not allow discernment between source and precursor signatures as the cause of the isotope anomalies. To overcome this problem,we obtained the first combined O, Ti,and Cr isotope data for individual chondrules from enstatite, ordinary, and carbonaceous chondrites. We find that chondrules from non-carbonaceous (NC) chondrites have relatively homogeneous ∆17O, ε50Ti, and ε54Cr, which are similar tothe compositions of their host chondrites. By contrast, chondrules from carbonaceous chondrites (CC)have more variable compositions, some of which differ from the host chondrite compositions. Although the compositions of CC and NC chondrules may overlap for either ε50Ti, ε54Cr, or ∆17O, in multi-isotope space CC chondrules never plot in the compositional field of NC chondrites, and NC chondrules never plot within the field of CC chondrites. As such, our data reveal a fundamental isotopic difference between NC and CC chondrules, which is inconsistent with adisk-wide transport of chondrules across and betweenthe NC and CC reservoirs. Instead, the isotopic variations among CC chondrules reflect local precursor heterogeneities, which most likely result from mixing between NC-like dust and a chemically diverse dust component that was isotopically similar to CAIs and AOAs. The same mixing processes, but on a larger, disk-wide scale, were likely responsible for establishing the distinct isotopic compositions of the NC and CC reservoirs, which represent in inner and outer disk, respectivel