Peters, Stefan T. M.

[["dc.bibliographiccitation.firstpage","70"],["dc.bibliographiccitation.journal","Earth and Planetary Science Letters"],["dc.bibliographiccitation.lastpage","79"],["dc.bibliographiccitation.volume","459"],["dc.contributor.author","Peters, Stefan T. M."],["dc.contributor.author","Muenker, Carsten"],["dc.contributor.author","Pfeifer, Markus"],["dc.contributor.author","Elfers, Bo-Magnus"],["dc.contributor.author","Sprung, Peter"],["dc.date.accessioned","2018-11-07T10:28:07Z"],["dc.date.available","2018-11-07T10:28:07Z"],["dc.date.issued","2017"],["dc.description.abstract","Some nuclides that were produced in supernovae are heterogeneously distributed between different meteoritic materials. In some cases these heterogeneities have been interpreted as the result of interaction between ejecta from a nearby supernova and the nascent solar system. Particularly in the case of the oldest objects that formed in the solar system - Ca-Al rich inclusions (CAls) - this view is confirm the hypothesis that a nearby supernova event facilitated or even triggered solar system formation. We present Hf isotope data for bulk meteorites, terrestrial materials and CAIs, for the first time including the low-abundance isotope Hf-174 (similar to 0.16%). This rare isotope was likely produced during explosive 0/Ne shell burning in massive stars (i.e., the classical \"p-process\"), and therefore its abundance potentially provides a sensitive tracer for putative heterogeneities within the solar system that were introduced by supernova ejecta. For CAls and one LL chondrite, also complementary W isotope data are reported for the same sample cuts. Once corrected for small neutron capture effects, different chondrite groups, eucrites, a silicate inclusion of a JAB iron meteorite, and terrestrial materials display homogeneous Hf isotope compositions including 174Hf. Hafnium-174 was thus uniformly distributed in the inner solar system when planetesimals formed at the <50 ppm level. This finding is in good agreement with the evidently homogeneous distributions of p-process isotopes W-180, Os-184 and possibly Pt-180 between different iron meteorite groups. In contrast to bulk meteorite samples, CAls show variable depletions in p-process 174Hf with respect to the inner solar system composition, and also variable r-process (or s-process) Hf and W contributions. Based on combined Hf and W isotope compositions, we show that CAls sampled at least one component in which the proportion of r- and s-process derived Hf and W deviates from that of supernova ejecta. The Hf and W isotope anomalies in CAls are therefore best explained by selective processing of presolar carrier phases prior to CAI formation, and not by a late injection of supernova materials. Likewise, other isotope anomalies in additional elements in CAIs relative to the bulk solar system may reflect the same process. The isotopic heterogeneities between the first refractory condensates may have been eradicated partially during CAI formation, because W isotope anomalies in CAls appear to decrease with increasing W concentrations as inferred from time -integrated (182)w/W-184. Importantly, the Lu-178-Hf-176 and Hf-182-W-182 chronometers are not significantly affected by nucleosynthetic heterogeneity of Hf isotopes in bulk meteorites, but may be affected in CAls. (C) 2016 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","DFG [MU1406/10-1/2]; Gottingen University [6125/3917543]"],["dc.identifier.doi","10.1016/j.epsl.2016.11.009"],["dc.identifier.isi","000393006500007"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/43354"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","1385-013X"],["dc.relation.issn","0012-821X"],["dc.title","Distribution of p-process Hf-174 in early solar system materials and the origin of nucleosynthetic Hf and W isotope anomalies in Ca-Al rich inclusions"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","346"],["dc.bibliographiccitation.journal","Geochimica et Cosmochimica Acta"],["dc.bibliographiccitation.lastpage","362"],["dc.bibliographiccitation.volume","239"],["dc.contributor.author","Elfers, Bo-Magnus"],["dc.contributor.author","Sprung, Peter"],["dc.contributor.author","Pfeifer, Markus"],["dc.contributor.author","Wombacher, Frank"],["dc.contributor.author","Peters, Stefan T. M."],["dc.contributor.author","Münker, Carsten"],["dc.date.accessioned","2019-07-24T07:38:21Z"],["dc.date.available","2019-07-24T07:38:21Z"],["dc.date.issued","2018"],["dc.description.abstract","The stepwise acid digestion of primitive chondritic meteorites allows the identification of nucleosynthetic isotope anomalies that are otherwise hidden on the bulk rock scale. Here, we present combined Hf and W isotope data for acid leachates, residues, and bulk rock aliquots of several primitive chondrites that include highly precise analyses of the heavy p-process isotopes ¹⁷⁴Hf and ¹⁸⁰W. Including data for these two p-process isotopes enables, for the first time, the clear-cut discrimination between s- and r-process contributions to the Hf and W isotope inventory. Our analyses reveal Hf and W isotopic homogeneity at the bulk rock scale, but significant Hf and W isotope anomalies that are complementary between acid leachates and residues. Since both r- to p-process isotope ratios are invariant in leachates and residues, the observed anomalies can unambiguously be tied to variable contributions of carrier phases enriched in s-process nuclides, as previously inferred for, i.e., Mo and Ru in leaching experiments. Hafnium and W isotope anomalies co-vary in leachate and residue fractions from CM chondrites, whereas CO and CV chondrites are characterized by distinctly larger Hf isotope anomalies compared to W. This observation is most likely explained by more efficient homogenization of s-process W carrier(s) or, alternatively, by local redistribution of anomalous W into secondary less resistant phases during parent body and/or nebular processing. This implies the presence of different s-nuclide carrier phases for Hf and W. Several carriers of s-process-material appear to have been selectively dissolved by our leaching protocol, while contributions from r- and p-process Hf and W carrier phases appear invariant, possibly due to the generally more labile nature of their carrier phases during solar nebula and/or parent body processing."],["dc.identifier.doi","10.1016/j.gca.2018.08.009"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/61964"],["dc.language.iso","en"],["dc.relation.issn","0016-7037"],["dc.title","Variable distribution of s-process Hf and W isotope carriers in chondritic meteorites – Evidence from 174Hf and 180W"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]