CHEMICAL CLASSIFICATION OF IRON METEORITES .3. HEXAHEDRITES AND OTHER IRONS WITH GERMANIUM CONCENTRATIONS BETWEEN 80-PPM AND 200-PPM

Concentrations of Ni, Ga, Ge and Ir are reported for 61 iron meteorites having Ge concentrations between 80 and 200 ppm. Four additional chemical groups are characterized as follows: {A table is presented} Groups IIB, IIC and IID are relatively small, whereas group IIA (consisting of single-crystal hexahedrites) includes about 11 % of known iron meteorites. In groups IIA, IIC and IID Ni, Ga and Ge are positively correlated with each other, and negatively correlated with Ir. In group HB Ga, Ge and Ir are positively correlated with each other, and inversely correlated with Ni. Groups IIA and IIB appear to be separate parts of a single differentiation sequence, and may have originated in the same parent body. Compositional data and cosmic-ray ages tentatively support this possibility, with low-Ni, high-Ir irons originating nearest to the center of the body. It is suggested that the variations in elemental concentrations observed in groups IIC and IID have originated in core-type fractionation processes, whereas nebular processes may have caused the compositional variations found within groups IIA and IIB. © 1969.