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

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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.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Smith, Thomas and Leya, Ingo


500 Science > 520 Astronomy
600 Technology > 620 Engineering








Dora Ursula Zimmerer

Date Deposited:

22 May 2019 13:30

Last Modified:

23 Oct 2019 18:30

Publisher DOI:






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