Correlated accretion ages and ε54Cr of meteorite parent bodies and the evolution of the solar nebula

We look at the relationship between the value of epsilon Cr-54 in bulk meteorites and the time (after calcium-aluminum-rich inclusion, CAI) when their parent bodies accreted. To obtain accretion ages of chondrite parent bodies, we estimated the maximum temperature reached in the insulated interior of each parent body, and estimated the initial Al-26/Al-27 for this temperature to be achieved. This initial Al-26/Al-27 corresponds to the time (after CAI formation) when cold accretion of the parent body would have occurred, assuming Al-26/Al-27 throughout the solar system began with the canonical value of 5.2x10(-5). In cases of iron meteorite parent bodies, achondrite parent bodies, and carbonaceous chondrite parent bodies, we use published isotopic ages of events (such as core formation, magma crystallization, and growth of secondary minerals) in each body's history to obtain the probable time of accretion. We find that epsilon Cr-54 correlates with accretion age: the oldest accretion ages (1 +/- 0.5Ma) are for iron and certain other differentiated meteorites with epsilon Cr-54 of -0.75 +/- 0.5, and the youngest ages (3.5 +/- 0.5Ma) are for hydrated carbonaceous chondrites with epsilon Cr-54 values of 1.5 +/- 0.5. Despite some outliers (notably Northwest Africa [NWA] 011 and Tafassasset), we feel that the correlation is significant and we suggest that it resulted from late, localized injection of dust with extremely high epsilon Cr-54.