Peters, Stefan T. M.

[["dc.bibliographiccitation.firstpage","132"],["dc.bibliographiccitation.journal","Chemical Geology"],["dc.bibliographiccitation.lastpage","145"],["dc.bibliographiccitation.volume","413"],["dc.contributor.author","Peters, Stefan T. M."],["dc.contributor.author","Muenker, Carsten"],["dc.contributor.author","Wombacher, Frank"],["dc.contributor.author","Elfers, Bo-Magnus"],["dc.date.accessioned","2018-11-07T09:50:10Z"],["dc.date.available","2018-11-07T09:50:10Z"],["dc.date.issued","2015"],["dc.description.abstract","Analytical protocols for measurements of isotope ratios involving low-abundance isotopes Hf-174 (similar to 0.16%), W-180 (similar to 0.12%), and Pt-190 (similar to 0.014%) usingmulti-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) at ca. tenfold improved precision compared to previous studies are presented. The improvements in precision result in part from the use of Faraday amplifiers equipped with 10(12) Omega resistors for collection of the isotope beams of interest, as well as for the isotope beams used to monitor isobaric interferences. For ion currents >5 x 10(-13) A (>50 mV on an amplifier with 10(11) Omega resistor), uncertainties (2 s. d.) of better than 100 ppm are typically achieved for isotope ratios involving Hf-174, W-180 and Pt-190. Terrestrial isotope abundances (atomic percent +/- 2 s.d.) of Hf-174 (0.16106 +/- 0.00006; n=15); W-180(0.11910 +/- 0.00009; n=10); and Pt-190 (0.01286 +/- 0.00005; n = 9) were determined on reference solutions throughout multiple analytical sessions over similar to 3 years. The results, however, rely on the accuracy of the reference value chosen for the isotope ratios employed for mass bias correction and, to a lesser extent, on the accuracy of the exponential mass fractionation law used for mass bias correction. For the precise determination of isotope ratios involving Hf-174, W-180 and Pt-190 in natural materials, efficient chromatographic separation schemes for Hf and W from silicate-rich matrices, and for Pt from iron meteorite matrices, are presented that provide effective separation of the element of interest from interfering elements. First results for Pt suggest that IAB, IIAB and IIIAB iron meteorites exhibit terrestrial Pt-190 abundances within uncertainty. Three chondrite samples exhibit indistinguishable Hf-174 from terrestrial Hf. The isotope abundance of W-180 in meteorites is more variable due to radiogenic W-180 that was produced by Os-184-decay. (C) 2015 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","DFG [MU 1406/10-1/2]"],["dc.identifier.doi","10.1016/j.chemgeo.2015.08.018"],["dc.identifier.isi","000361845700012"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/35653"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","1878-5999"],["dc.relation.issn","0009-2541"],["dc.title","Precise determination of low abundance isotopes (Hf-174, W-180 and Pt-190) in terrestrial materials and meteorites using multiple collector ICP-MS equipped with 10(12) Omega Faraday amplifiers"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["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","236"],["dc.bibliographiccitation.journal","Geochimica et Cosmochimica Acta"],["dc.bibliographiccitation.lastpage","239"],["dc.bibliographiccitation.volume","169"],["dc.contributor.author","Peters, Stefan T. M."],["dc.contributor.author","Muenker, Carsten"],["dc.contributor.author","Becker, Harry"],["dc.contributor.author","Schulz, Toni"],["dc.date.accessioned","2018-11-07T09:48:55Z"],["dc.date.available","2018-11-07T09:48:55Z"],["dc.date.issued","2015"],["dc.identifier.doi","10.1016/j.gca.2015.06.030"],["dc.identifier.isi","000362975700015"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/35406"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Pergamon-elsevier Science Ltd"],["dc.relation.issn","1872-9533"],["dc.relation.issn","0016-7037"],["dc.title","Comment on \"Cosmogenic W-180 variations in meteorites and re-assessment of a possible Os-184-W-180 decay system\" by Cook, DL, Kruijer, T., Leya, I., Kleine, T."],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.subtype","letter_note"],["dspace.entity.type","Publication"]]