Pu–Xe, U–Xe, U–Pb chronology and isotope systematics of ancient zircons from Western Australia

r-PROCESS PRODUCTION SITES AS INFERRED FROM Eu ABUNDANCES IN DWARF GALAXIES

“…In addition, Hotokezaka et al (2015) have shown that the rarity of r-process events is broadly consistent with 244 Pu abundances of both the early solar system material (Turner et al 2007) and the present-day deep-sea archives (Wallner et al 2015), which are difficult to explain otherwise. The r-process element enrichment in halo stars with very low metallicities, proposed as a problem for this scenario (Argast et al 2004), can be resolved by taking into account the turbulent mixing of material in the galaxy (Piran et al 2014), the assembly of sub-halos during the formation of the Galaxy (Komiya et al 2014;van de Voort et al 2015;Ishimaru et al 2015;Shen et al 2015), the large typical distances between the locations of the stellar collapses and the eventual mergers as well as the likely possibilities of rapid mergers and stellar collapses with small amounts of mass ejecta .…”

Short-Lived 244Pu Points to Neutron Star Binary Mergers as Sites for r-Process Nucleosynthesis

“…1). The allowed region inferred from the 244 Pu abundance in the deep-sea floor [9] and the ESS [10,13] is shown as a blue region. The blue solid (dotted) line corresponds to the current ISM 244 Pu density being the median (2σ) value.…”

“…These values are significantly lower than the number density in the ISM determined from the ESS 244 Pu abundance: n Pu ≈ ( 244 Pu/ 238 U) ESS Y U, ESS n ISM ∼ 6 × 10 −15 cm −3 . The relative abundance ratio of ( 244 Pu/ 238 U) ESS ≈ 0.008 is estimated from fissiogenic xenon in ESS material [10]. Y U, ESS = 7.3×10 −13 is the number abundance of 238 U relative to hydrogen inferred from meteorites ( [13] ; corrected from the present for 238 U decay) and n ISM is the mean number density of the ISM, which is typically ≈ 1 cm −3 .…”

“…Radioactive elements, with the right lifetime can break the degeneracy between highrate/low-yield and low-rate/high-yield scenarios. Among radioactive elements most interesting is 244 Pu (half-life of 81 Million years) for which both the current accumulation of live 244 Pu particles accreted via interstellar particles in the Earth's deep sea floor [9] and the Early Solar System (ESS) abundances have been measured [10]. Interestingly, the estimated 244 Pu abundance in the current interstellar medium (ISM) inferred from deep-sea measurements is significantly lower than that corresponding to the ESS measurements.…”

Reply to Comment on “Pervasive remagnetization of detrital zircon host rocks in the Jack Hills, Western Australia and implications for records of the early dynamo”

“…B. Weiss and J. Kirschvink collected the three EHJH blocks in the Jack Hills in 2001 with R. Pidgeon, T. M. Harrison, and S. Mojzsis; the first is the co-discoverer of the Erawandoo Hill Hadean zircon original discovery outcrop (Compston and Pidgeon, 1986) and all three have studied the outcrop extensively (Bell et al, 2015;Compston and Pidgeon, 1986;Dunn et al, 2005;Grange et al, 2010;Harrison, 2009;Holden et al, 2009;Hopkins et al, 2008;Hopkins et al, 2010;Kemp et al, 2010;Mojzsis, 2007;Mojzsis et al, 2001;Pidgeon, 1992Pidgeon, , 2014Pidgeon and Wilde, 1998;Spaggiari et al, 2007;Trail et al, 2016;Trail et al, 2011;Turner et al, 2007;Turner et al, 2004;Watson and Harrison, 2005;Wilde and Pidgeon, 1990)] (Fig. S2 and Table S4).…”