METAL—OLIVINE ASSOCIATIONS AND Ni—Co CONTENTS IN TWO APOLLO 12 MARE BASALTS

Olivine crystals in mare basalts 12004,8 and 12022,12 are normally zoned with Cr-poor rims. The Ni content of rare 2—10-jim metal inclusions in olivine decreases markedly as Fe/Mg in their immediate olivine hosts increases. Each metal grain appears to have been enclosed by late olivine almost immediately after it crystallized. The frac tionation trend for the olivine and metal contrasts with the subsolidus equilibration trend for pallasites. For the basalts, not even local equilibration of Fe, Ni and Co at metal/olivine interfaces can be detected by microprobe. Ni and Co concentrations range from about 300 ppm in olivine cores to about 70 ppm in rims. The limits of detec tion,