Chemical compositions of refractory inclusions in the Murchison C2 chondrite

Neutron activation has been used to analyze samples from ten refractory inclusions in Murchison for 36 elements. Two inclusions, BB-5 and MUCH-1, have large negative Yb anomalies unaccompanied by correspondingly large and negative Eu anomalies; six inclusions have group II or III patterns, or variants of such patterns. The frequency of highly fractionated REE patterns, and the absence of group I patterns, suggest that refractory inclusions in Murchison stopped equilibrating with the nebular gas at higher temperatures than most Allende coarse grained inclusions. Murchison inclusions tend to be lower in nonrefractory elements than Allende coarse grained inclusions, further suggesting that, on average, the former underwent less severe secondary alteration than the latter.