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Title: ZIRCONIUM—HAFNIUM ISOTOPE EVIDENCE FROM METEORITES FOR THE DECOUPLED SYNTHESIS OF LIGHT AND HEAVY NEUTRON-RICH NUCLEI

Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope {sup 96}Zr (≤1ε in {sup 96}Zr/{sup 90}Zr) for bulk chondrites and CAIs (∼2ε). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the {sup 96}Zr isotope variations are of nucleosynthetic origin. The {sup 96}Zr enrichments are coupled with {sup 50}Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A ≤ 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavymore » r-process isotopes. In the context of our model, the light isotopes (e.g. {sup 96}Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M{sub ☉}) SNII.« less
Authors:
;  [1] ;  [2] ;  [3]
  1. School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)
  2. Institut für Planetologie, Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany)
  3. Institute for Geochemistry and Petrology, ETH, Clausiusstrasse 25, 8092 Zürich (Switzerland)
Publication Date:
OSTI Identifier:
22270555
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 777; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; CARBON MONOXIDE; CHARGED-PARTICLE REACTIONS; CHONDRITES; HAFNIUM ISOTOPES; ISOTOPE EFFECTS; METEOROIDS; NEUTRON REACTIONS; NEUTRON-RICH ISOTOPES; NUCLEOSYNTHESIS; R PROCESS; ROCKS; S PROCESS; SOLAR SYSTEM; SPALLATION; SUPERNOVAE; TITANIUM 50; VISIBLE RADIATION; ZIRCONIUM 90; ZIRCONIUM 96