Abstract
Distributions of trace ruthenium (Ru) in submilimeter sized areas of metallic FeNi minerals in iron meteorites have been studied by microbeam X-ray fluorescence analysis using synchrotron orbital radiation (SR-XRF) at Photon Factory, National Laboratory for High Energy Physics, Japan. Samples of iron meteorites of groups IA and IIA were irradiated by monochromatized X-ray beam of 22.5 and 23.0 KeV with beam size of 0.5×0.5 to 0.25×0.25 mm squares. A calibration curve was constructed for the standard FeNi alloys doped with 10 to 1000 ppm Ru. The Ru concentrations of ALH77283 (IA) kamacites were analyzed to be about 3 and 5 ppm. Ru in group IIA analyzed in this study (Bennett County, Coahuila, Scottsville, and Walker County) ranges from 13 to 33 ppm. These Ru concentrations of group IIA fall within the range of IIA previously reported. This study has shown that the non-destructive SR-XRF method can easily determine Ru concentration in iron meteorites, and that this method can be used to classify iron meteorites of groups IA and IIA on the basis of Ru versus Ni diagram.
