NITROGEN ISOTOPIC COMPOSITIONS OF IRON-METEORITES

Iron meteorites analyzed in this study have nitrogen concentrations le ss-than-or-equal-to 70 mug/g and deltaN-15 from -90 to +150 parts per thousand. Although the iron meteorites have a large range of deltaN-15 . most have values more negative than -50 parts per thousand. The nitr ogen isotopic compositions were established by cosmochemical processes and were little modified by fractional crystallization or other chemi cal processes within the parent bodies. The data do not suggest the ex istence of a well-mixed solar nebular reservoir for nitrogen, as was a lready inferred from data from stony meteorites. The range of > 1100 p arts per thousand observed for deltaN-15 in bulk meteorites is probabl y too large to be accounted for by physical and chemical mass-dependen t fractionation processes in the solar nebula, and thus reflects nebul ar inhomogeneities of nucleosynthetic origin. Nitrogen isotopes may se rve as fingerprints for different reservoirs, preserved in various par ent bodies, in a manner similar to that observed for oxygen isotopes i n stony meteorites, and oxygen-bearing phases of stony irons.