Because of their similarities in chemical (siderophile elements in metal) and oxygen isotope compositions, it has been suggested that the IIIAB-irons and main group (MG) pallasites formed the core and core-mantle interface in a single asteroid. Mantle olivine appears to have been crushed and invaded by a IIIAB-like magma. We review the petrological and chemical characteristics of pallasites and IIIAB irons and report preliminary result of our instrumental neutron activation analysis (INAA) data for pallasites and related meteorites. As inferred by Scott, metal compositions of MG pallasites can be largely modeled as the residual liquid present during crystallization of IIIAB irons. However, several volatile elements are higher than expected in the IIIAB liquid, suggesting transport through a coexisting gas phase. Our INAA data of metal from Brahin, Vermilion, and Yamato 8451, which have similar oxygen isotope compositions, shows them to be mutually unrelated.
Lunar and Planetary Science Conference
- Pub Date:
- March 1996
- CRYSTALLIZATION: FRACTIONAL;
- METEORITES: IIIAB IRON;