Supernova sources and the 92Nb-92Zr p-process chronometer

We report new Zr isotope evidence for live (92)Nb (mean life: <(tau)over bar>(92Nb) = 52 Myr) within the early solar system resulting in ((92)Nb/(93)Nb)(initial) approximate to 10(-3). The meteoritic minerals rutile and zircon have, respectively, very high and very low Nb/Zr ratios and are ideal for exploring the (92)Nb-(92)Zr chronometer. Rutiles exhibit high positive epsilon(92Zr) (similar to 14-36) while a zircon has a negative epsilon(92Zr) (similar to-4), as would be expected if 92Nb was live in the early solar system. The meteoritic rutiles appear to be young, with apparent times of formation of similar to 80-220 Myr subsequent to the origin of the solar system. The initial (92)Nb/(92)Mo for the solar system is broadly compatible with a model of uniform production if the 92Nb/92Mo production ratio for Type II supernova (SNII) sources with neutrino-driven winds is used. Data for all the now extinct p-process nuclides ((92)Nb, (97)Tc and (146)Sm) are consistent with these isotopes being derived by uniform production from SNII sources and a free decay interval of similar to 10 Myr. Consideration of a range of models indicates that the average p-process production ratio of 92Nb/92Mo needs to be at least in the range of 0.06-0.25.