Parent-body models for the formation of iron meteorites.

The iron meteorites appear to have formed by both igneous and non-igneous processes in asteroid-sized parent bodies. Evidence regarding the IIIA-IIIB irons (the most common iron meteorite group) favors their having originated as a central core, which experienced fractional crystallization during solidification. A reevaluation of available data does not confirm earlier reports of variable cooling rates within group IIIA. Members of group IA-IB contain chondritic silicates, have short I-Xe formation intervals and do not show evidence of fractional crystallization. They appear to have formed nonigneously by inhomogeneous agglomeration and accretion of solar nebular condensates.