| Abstract: | Olivine grains were analysed by microprobe for Si, Ca, Mg, and Fe. Distribution of Mg and Fe is similar to that already established for Type II and III carbonaceous chondrites. Calcium concentration varies by a factor of about 4 and seems to be independent of fayalite content: its range (about 0.1 ? 0.45 weight percent) resembles that in the olivines of Murray (Fredriksson and Keil, 1964). Olivines of carbonaceous chondrites are the product of mechanical mixing of pre-existing crystals (Van Schmus, 1969). More than one fractionation process is necessary to account for Ca variation superimposed on Mg:Fe fractionation observed in Murray, Murchison and Vigarano. |
