Isotope anomalies in tellurium and palladium from Allende nanodiamonds

Abstract

Abstract— ‐The elemental and isotopic abundances of Te and Pd have been measured by thermal ionization mass spectrometry in a purified sample of interstellar nanodiamonds from the Allende meteorite, after combustion of the diamonds in an oxygen plasma. Small positive anomalies were found in 128Te (4.0 ± 1.5 %0) and 130Te (9.3 ± 2.8 %0) from three analyses of the Allende nanodiamond sample EB, and in 110Pd (9.4 ± 5.7 %0) from two analyses of the same sample. No other anomalies of a significant nature were found in either Te or Pd. These results are consistent with the neutron burst model (Meyer et al., 2000), and the r‐process based rapid separation model of Ott (1996) in that 128, 130Te and 110Pd are enhanced relative to their solar abundances. However, in the framework of the neutron burst model, some separation between stable products and radioactive precursors may be required in order to be consistent with the full data set of Te isotopes. In the framework of the rapid separation scenario, our data suggests a separation time of approximately 4000 s, based on the magnitudes of the precursor life‐times for 128Te and 130Te. The elemental abundance ratio Te‐H/Xe‐H agrees with the prediction of the rapid separation model, provided little fractionation occurred during trapping of the exotic components by the diamonds, but differs significantly from expectations based on the neutron burst model. Differences in the inferred 128Te/130Te ratio between our work and that of Richter et al. (1998) point to the need for further investigations.