Homogeneity of Tellurium Isotopes in Chondrites, Leachates of Allende and Canyon Diablo

Introduction: Sn decays to Te with a half-life of 0.235 Myrs and is a possible short-lived chronometer for early solar system development. Sn can only be produced in significant amounts by the r-process, which is thought to take place in a supernova environment. The discovery of Te excesses that correlate with Sn/Te in meteorites would thus provide confirmation of the theory that a supernova injected freshly synthesised nuclides into the molecular cloud from which our solar system formed and served as a trigger for nebula collapse. Tellurium is also of interest because it has eight stable nuclides that are suited for the study of nucleosynthetic processes. The nuclide Te is produced only by the p-process, Te only by the s-process, 128, Te only by the r-process, whereas 125, Te are produced by the rand s-process. Previous studies have reported large (100%-level) Te isotope anomalies in presolar diamonds of Allende [1], [2]. Bulk chondrites and iron meteorites measured by TIMS are homogeneous in Te isotopes [3]. For Te isotopic measurements, MC-ICPMS achieves a precision, which is one to two orders of magnitudes better than that of TIMS [4], [5]. Bulk carbonaceous chondrites measured by MC-ICPMS were all found to be identical in Te isotope composition to the Earth [5]. Assuming the bulk Sn/Te ratios of carbonaceous chondrites reflect variable early volatile element depletion during condensation in the nebula that represent their parent bodies, we calculated a maximum possible initial Sn/Sn of 1x10 [5].