Abstract
He 3, He 4, Ne 21 and Ar 38 contents were determined in 18 metal, troilite, sehreibersite and graphite inclusions of 9 iron meteorites, by total outgassing and stepwise heating. The He 4 He 3 ratio in metal phase ranges from 3.85 to 4.65, but in non-metallic samples, from 6.70 to 30.5. The results for cosmogenic isotopes of helium, neon and argon disagree appreciably with data on accelerator-irradiated targets. It should be noted, however, that some inclusions have lost considerable amounts of gas by diffusion. Uranium contents of 22 troilite and sehreibersite samples were determined by the fission track technique. The average uranium content of troilite is 0.4-0.7 ppb. Excess He 4 of unknown origin was observed in troilite inclusions. If one assumes that the excess He 4 was produced by uranium decay in situ, then the apparent U-He 4 age is at least 5.9 × 10 9 yr.
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