Edelgasmessungen an Eisenmeteoriten und deren Einschlüssen

Abstract

The isotopes of He, Ne, and Ar have been measured in a number of iron meteorites and their troilite and schreibersite inclusions using a statically operated omegatron-type mass spectrometer. In the metal samples the isotopic ratios are in general agreement with expectations based on the curves given by Signer and Nier. An excess of (13 ± 2) ·10-8 cc STP 4He/g —which might be of radiogenic origin—is indicated, however, in the case of Cranbourne, a large meteorite with a radiation age 27 · 106 a < T8 < 70 · 106 a. Similar amounts appear to be present in several other iron meteorites as well. — Variations in the 38Ar/21Ne-ratios due to different effective energy spectra are not parallelled by similar changes in the 38Ar/38Ar-ratios. The data, combined with those of Signer and Nier and Heymann, Lipschutz, Nielsen, and Anders show the reason to be a simultaneous shift of the yield curve along the isobar M=36, the trend being in agreement with results from target experiments. — For the He and Ne produced on S the ratios 3He/4He ≧ 0.112 and 20Ne:21Ne: 22Ne = 1.12 : 1.00 : 1.21 were obtained while the production rates of 3He, 4He, 20Ne, 21Ne, and 22Ne on S relative to iron were found to be 0.75 ± 0.2, ≦ 1.79, 7.8 ± 1.3, 7.35 ± 1.2, and 8.3 ± 1.4, resp. Possible reasons for the unexpectedly high production rate of 20Ne are being discussed.