Isotopically anomalous silver in the Santa Clara and Piñon iron meteorites

Publisher Website
Google Scholar
Abstract
The isotopic composition and concentration of Ag and the concentration of Pd have been determined in the Santa Clara and Piñon iron meteorites. It is shown that these meteorites contain isotopically anomalous Ag with an excess of 107Ag relative to normal Ag, confirming earlier findings. Using an improved procedure for cleaning the sample surface from terrestrial Ag, a new concentration of 1‐4×1011 atoms of 109Ag/g meteorite is established which is an order of magnitude below the levels found earlier. As a result ratios of 107Ag/109Ag were found which are enriched in 107Ag by 60% to 160%. The existence of an excess 107Ag in these two meteorites, which have high 108Pd/109Ag ratios of ∼ 7×104, is established. These findings are consistent with the in situ decay of extinct 107Pd (τ½ = 6.5×106y) produced by a late nucleosynthetic event shortly before solar system formation; however, production of Ag isotopes by reaction of cosmic ray secondaries with the Pd isotopes in the meteorites cannot be excluded.