Hf-W chronology of CR chondrites: Implications for the timescales of chondrule formation and the distribution of Al-26 in the solar nebula

摘要

Renazzo-type carbonaceous (CR) chondrites are distinct from most other chondrites in having younger chondrule Al-26-Mg-26 ages, but the significance of these ages and whether they reflect true formation times or spatial variations of the Al-26/Al-27 ratio within the solar protoplanetary disk are a matter of debate. To address these issues and to determine the timescales of metal-silicate fractionation and chondrule formation in CR chondrites, we applied the short-lived Hf-182-W-182 chronometer to metal, silicate, and chondrule separates from four CR chondrites. We also obtained Mo isotope data for the same samples to assess potential genetic links among the components of CR chondrites, and between these components and bulk chondrites.