Cosmic-ray-produced S36and S33in the metallic phase of iron meteorites

Isotopic analysis of sulfur in the iron phase of a number of meteorites has shown the presence of cosmic-ray-produced spallation S36 and S33. The Clark County meteorite sample yielded about 6×10−5μg/g of Ssp36 and about 3×10−4μg/g of Ssp33; samples from the Piñon and Tlacotepec meteorites yielded about 8×10−6 μg/g of Ssp36 and about 2×10−5 μg/g of Ssp33. Spallation sulfur in the Carbo meteorite was diluted considerably by larger quantities of natural sulfur, but it is probable that Ssp36 is about 2×10−5 μg/g. Significant quantities of Ssp36 or Ssp33 could not be detected in samples from the Canyon Diablo and Xiquipilco (Toluca) meteorites. These spallation results are in reasonable agreement with predictions based on production rates of the rare gases in these meteorites according to cascade theory for the He isotopes and the Rudstam formula for the Ar isotopes. Detailed comparison of the distribution of the spallation products among the isobars of mass 36 will not be feasible until it is possible to develop methods of increasing the precision of these spallation sulfur measurements.