Excess ¹⁸ºW in IIAB iron meteorites: Identification of cosmogenic, radiogenic, and nucleosynthetic components

Cook, David L.; Smith, Thomas; Leya, Ingo; Hilton, Connor D.; Walker, Richard J.; Schönbächler, Maria (2018). Excess ¹⁸ºW in IIAB iron meteorites: Identification of cosmogenic, radiogenic, and nucleosynthetic components. Earth and planetary science letters, 503, pp. 29-36. Elsevier 10.1016/j.epsl.2018.09.021

Text 1-s2.0-S0012821X18305600-main.pdf - Published Version Restricted to registered users only Available under License Publisher holds Copyright. Download (569kB)

The origin of ¹⁸ºW excesses in iron meteorites has been a recently debated topic. Here, a suite of IIAB iron meteorites was studied in order to accurately determine the contribution from galactic cosmic rays (GCR) and from potential decay of ¹⁸⁴Os to measured excesses in the minor isotope ¹⁸ºW. In addition to W isotopes, trace element concentrations (Re, Os, Ir, Pt, W) were determined on the same samples, as well as their cosmic ray exposure ages, using ³⁶Cl–³⁶Ar systematics. These data were used in combination with an improved model of GCR effects on W isotopes to correct effects resulting from neutron capture and spallation reactions. After these corrections, the residual ¹⁸ºW excesses correlate with Os/W ratios and indicate a clear contribution from ¹⁸⁴Os decay. A newly derived decay constant is equivalent to a half-life for ¹⁸⁴Os of (3.38 ± 2.13) × 10¹³ a. Furthermore, when the data are plotted on an Os–W isochron diagram, the intercept (ε¹⁸ºWᵢ = 0.63 ± 0.35) reveals that the IIAB parent body was characterized by a small initial nucleosynthetic excess in ¹⁸ºW upon which radiogenic and GCR effects were superimposed. This is the first cogent evidence for p-process variability in W isotopes in early Solar System material.

Interest & Impact

Downloads

4 since deposited on 22 May 2019
0 in the past 12 months

Citations

5 Citations in Web of Science ®
6 Citations in Scopus

Search

in Google Scholar™

Services

Actions (login required)

Edit item

Actions (login required)

Edit item