ORIGIN OF EXCESS {sup 176}Hf IN METEORITES

Journal Article · Sat Jul 10 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/717/2/861· OSTI ID:21457123

Thrane, Kristine; Connelly, James N; Bizzarro, Martin ^[1]; Meyer, Bradley S; The, Lih-Sin ^[2]

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1. Geological Museum, University of Copenhagen, Oester Voldgade 5-7, DK-1350 (Denmark)
2. Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978 (United States)

After considerable controversy regarding the {sup 176}Lu decay constant ({lambda}{sup 176}Lu), there is now widespread agreement that (1.867 {+-} 0.008) x 10{sup -11} yr{sup -1} as confirmed by various terrestrial objects and a 4557 Myr meteorite is correct. This leaves the {sup 176}Hf excesses that are correlated with Lu/Hf elemental ratios in meteorites older than {approx}4.56 Ga meteorites unresolved. We attribute {sup 176}Hf excess in older meteorites to an accelerated decay of {sup 176}Lu caused by excitation of the long-lived {sup 176}Lu ground state to a short-lived {sup 176m}Lu isomer. The energy needed to cause this transition is ascribed to a post-crystallization spray of cosmic rays accelerated by nearby supernova(e) that occurred after 4564.5 Ma. The majority of these cosmic rays are estimated to penetrate accreted material down to 10-20 m, whereas a small fraction penetrate as deep as 100-200 m, predicting decreased excesses of {sup 176}Hf with depth of burial at the time of the irradiation event.

• OSTI ID: 21457123
• Journal Information: Astrophysical Journal, Vol. 717, Issue 2; Other Information: DOI: 10.1088/0004-637X/717/2/861; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COSMIC RADIATION
CRYSTALLIZATION
HAFNIUM 176
LUTETIUM 176
METEORITES
NUCLEAR DECAY
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DECAY
EVEN-EVEN NUCLEI
HAFNIUM ISOTOPES
HOURS LIVING RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IONIZING RADIATIONS
ISOTOPES
LUTETIUM ISOTOPES
NUCLEI
ODD-ODD NUCLEI
PHASE TRANSFORMATIONS
RADIATIONS
RADIOISOTOPES
RARE EARTH NUCLEI
STABLE ISOTOPES
YEARS LIVING RADIOISOTOPES