ausblenden:
Schlagwörter:
Earth Science
Zusammenfassung:
Peters et al. (2014) argued that ɛ180W excesses in iron meteorites originated as the decay product of 184Os. They also suggested that compositional heterogeneities, leading to variable Os/W ratios within a single iron, was the most likely explanation for discrepant ɛ180W values measured in different studies of the same meteorites. In Cook et al. (2014), we showed that irradiation by galactic cosmic rays (GCR) can induce large variations in ɛ180W. These effects provide at least a partial explanation for the observed ɛ180W excesses. Additionally, they can explain why ɛ180W values may vary both among members of a particular iron meteorite group (e.g., IVB irons), as well as between different specimens of a single iron meteorite (e.g., Weaver Mountains). We used GCR-corrected ɛ180W data to re-estimate the possible role of 184Os decay in generating ɛ180W excesses and found that any radiogenic production of 180W was much smaller than suggested by Peters et al. (2014). The preceding comment by Peters et al. (2015) on our 2014 paper contains criticisms that focus mainly on the following topics: the influence of an s-process deficit in W isotopes on ɛ180W in some iron meteorites, our sample selection for the construction of our isochron, and the potential effect of sample compositional heterogeneity on Os/W ratios and how this may impact our isochron slope. We address each of these in turn below.
