Intrinsic W nucleosynthetic isotope variations in carbonaceous chondrites: Implications for W nucleosynthesis and nebular vs. parent body processing of presolar materials
Christoph Burkhardt, Maria Schönbächler
In Press, Accepted Manuscript, Available online 20 June 2015
The overall magnitude of the W isotope variations decreases in the order CI1>CM2>CV3. This can be interpreted as the progressive thermal destruction of an initially homogeneous mixture of presolar grains by parent-body processing. However, not only the magnitude but also the W anomaly patterns of the three chondrites are different. In particular leach step 2, that employs nitric acid, reveals a s-deficit signature for Murchison, but a s-excess for Orgueil and Allende. This could be the result of redistribution of anomalous W into a new phase by parent-body alteration, or, the fingerprint of dust processing in the solar nebula. Given that the thermal and aqueous alteration of Murchison is between the CI and CV3 chondrites, parent-body processing is probably not the sole cause for creating the different patters. Small-scale nebular redistribution of anomalous W may have played a role as well. Similar nebular processes possibly acted differently on specific carrier phases and elements, resulting in the diverse nucleosynthetic signatures observed in planetary materials today.