00167037/84/13.00 +.oo Chemical compositions of refractory inclusions in the Murchison C2 chondrite VANAVAN EKAMBARAM, IWAO KAWABE’, TSUYOSHI TANAKA’,

Abstract-Samples from ten refractory inclusions in Murchison, some of which are splits of inclusions whose mineralogical and petrographic haracteristics are known, have been analysed for thirty-six elements by neutron activation. Six inclusions have group II or group III patterns or variants of such patterns. Two inclusions, BBS and MUCH- I, have large negative Yb anomalies unaccompanied by correspondingly arge negative Eu anomalies. It is possible that the latter condensed originally with group III patterns and preferentially took up Eu in later exchange processes under raking conditions. One inclusion, SH-2, has heavy REE enrichment factors that increase with the refractoriness of the REE, indicating the presence of an extremely high-temperature, or ultramfiactory, REE condensate, but it also has a heavy REE/light REE ratio that indicates mixing of that component with a lower-temperature REE condensate. The frequency of hiily fractionated REE patterns and absence of group I patterns uggest that refractory inclusions in Murchison stopped equihbrating with the nebular gas at higher temperatures than most Allende coarse-grained inclusions. The lower Ir/Os and Ru/Re ratios of some Murchison inclusions compared to those of Allende coarse&tied inclusions indicate that condensate alloys that contributed noble metals to the former also stopped equitibrating with the nebular gas at higher temperatures than those that contributed noble metals to the latter. Murchison indusions tend to be lower in non-refractory elements than Allen& coarse-grain & inclusions, suggesting that, on average, the former underwent less severe secondary alteration than the latter