Isotope genealogy and chronology of individual chondrules from ordinary chondrites

Chondrules are a ubiquitous high-T component in primitive meteorites, and as such are key for reconstructing the evolution of dust in the accretion disk surrounding the young Sun. To better constrain the composition of the inner, non-carbonaceous (NC) disk reservoir, and ultimately the source material and growth history of the terrestrial planets, we present here a comprehensive petrographic, chemical, O, Ti, and Cr isotopic, and Al-Mg and Mn-Cr chronometric study of chondrules extracted from ordinary chondrites. We find that chondrules of different textures and chemical compositions (Mg# 67-99) exhibit a narrow range of O, Ti, and Cr isotopic variations. Only one chondrule exhibits ε⁵⁰Ti and ε⁵⁴Cr values that are outside the range of bulk NC materials, likely due to the presence of AOA-like material in its precursor assemblage. Internal Al-Mg isochrons yield an average age of ~1.8±0.6 (2sd) Myr after the start of the Solar System, in line with an age of ~2.2±0.8 Myr obtained from a Mn-Cr bulk chondrule isochron. Overall, the data suggest that the majority of the OC chondrules formed at around 2 Myr after the start of the Solar System in a well-mixed reservoir dominated by NC dust, with only little contribution of anomalous materials from the outer Solar System. This implies that the parent bodies of NC chondrites predominantly accreted dust from their local orbit, and that the barrier separating the inner and outer disk effectively blocked the passage of ~mm-sized dust.