Ruthenium Isotope Composition of Allende Refractory Metal Nuggets

Mario Fischer-Gödde1,2, Daniel Schwander3, and Ulrich Ott4,5
The Astronomical Journal 156, 176 Link to Article []
1Institut für Geologie und Mineralogie, Universität zu Köln, Zülpicher Str. 49b, D-50674 Köln, Germany
2Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany
3Steinmann-Institut, Rheinische Friedrich-Wilhelms-Universität, Meckenheimer Allee 169, D-53115 Bonn, Germany
4MTA Atomki, Bem tér 18/c, HU-4026 Debrecen, Hungary
5Max-Planck-Institut für Chemie, Hahn-Meitner-Weg 1, D-55128 Mainz, Germany

Refractory metal nuggets (RMNs) are among the first solids formed in the nascent solar system. They contain high abundances of refractory metals like Re, Os, W, Ir, Ru, and Pt. The isotopic compositions of these elements bear testimony to the stellar sources that contributed to the nucleosynthetic makeup of our solar system. We report the first high-precision Ru isotope data for a bulk RMN sample prepared from the Allende meteorite. The RMNs display well-resolved mass-independent anomalies with positive anomalies for 96Ru, 98Ru, 100Ru, 102Ru, and 104Ru. These are best explained by a deficit in r-process combined with a slight deficit in p-process nuclides. This finding stands in stark contrast to the s-process deficit isotopic patterns observed for Allende Ca–Al-rich inclusions (CAIs), bulk Allende, and other bulk meteorites. The contrasting r-, p-deficit versus s-deficit Ru isotopic signatures observed between RMNs and CAIs is surprising, given that CAIs are assumed to be a major host phase of RMNs. One way to explain the s-deficit patterns observed for CAIs and bulk meteorites is that r– and p-process Ru nuclides were added to the solar nebula after RMN formation and prior to the formation of CAIs and the accretion of meteorite parent bodies. A possible source may have been a nearby core-collapse supernova that injected freshly synthesized r– and p-process nuclides into the nascent solar system. The injection of such r– and p-enriched matter represents an alternative mechanism to account for the s-process variability presented by CAIs and bulk carbonaceous meteorites.


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