The geochemical coherence of Pu and Nd and the 244Pu/238U ratio of the early solar system

Two very different sets of 244Pu/238U ratios have been reported for early solar system materials. One group of samples yields high (0.015 to 0.016) ratios (Podosek, 1970, 1972; Drozd et al., 1977) and calculations based on another group of analyses yield low ratios (approximately 0.004) (Marti et al., 1977). Recently measured partition coefficients for Pu and Sm are used to evaluate the data of Marti et al., and 244Pu/238U ratios from other sources are also considered. A low 244Pu/238U ratio (approximately 0.005) is favored, and some implications of this low ratio to galactic nucleosynthesis and meteorite age dating are briefly discussed. (author)