FE, NI AND CO VARIATIONS IN THE METALS OF SOME ANTARCTIC CHONDRITES

Nearly 4,000 Fe, Ni and Co analyses have been carried out on the metal phases of 12 Antarctic chondritic meteorites by means of the electron microprobe. H-group chondrites show relatively simple patterns of var iation for these elements but L- and LL-group members show much more s catter in both Ni and Co concentrations. A single member of the C03 gr oup investigated shows some scatter in the concentrations and also muc h higher Co concentrations in the high-Ni (awaruite?) phase (1.25-2%) than in the coexisting kamacite (0.2-0.5%). Thus, analysis of the meta l phases can provide not only a means of identifying the group to whic h a meteorite belongs, but also the possibility of distinguishing betw een individual chondrites from the same group. The overall concentrati ons of Co in the metal particles in the different groups are considere d to be related inversely to the abundance of metal grains in meteorit es of these groups while the scatter is interpreted as reflecting char acteristics inherited at the time of accretion. The absence of homogen isation of the concentrations of Fe, Ni and Co in the metal particles, even in so-called equilibrated chondrites, provides further evidence against the widely held notion that these meteorites have been involve d in a high-temperature prograde metamorphism.