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Determinations of osmium isotope ratios in iron meteorites and iridosmines by ICP-MS.

1986; The Geochemical Society of Japan; Volume: 20; Issue: 5 Linguagem: Inglês

10.2343/geochemj.20.233

1880-5973

Akimasa Masuda, Takafumi Hirata, Hiroshi Shimizu,

Astro and Planetary Science

Osmium isotopes in three Os reagents, four terrestiral Os-Ir alloys (iridosmine) and two iron meteorites have been measured on an inductively coupled plasma mass spectrometer (ICP-MS), with the precision of around 1% for 187Os/192Os. Comparisons are made of our isotopic ratios with the previous ones. Apart from the variation of 187Os abundance as naturally expected, there seems to be a slight systematic deviation for 189Os. Also some discussions are given to 184Os. The Os isotopic ratios for three iridosmine samples from Hokkaido, Japan, have been found quite similar to each other. The values for the Hokkaido iridosmines are 3–4% higher relative to the straight 187Os growth line obtained by Allegre and Luck (1980). Finally, the isotopic “standard” abundances (%) for Os are presented by us: 184Os, 0.019; 186Os, 1.589; 187Os, 1.519; 188Os, 13.24; 189Os, 16.37; 190Os, 26.30; 192Os, 40.96. These give us the Os atomic weight = 190.24.