The histories of ordinary chondrite parent bodies - U, Th-He age distributions

Journal Article · Sat Jun 01 00:00:00 EDT 1991 · Meteoritics; (United States)

DOI:https://doi.org/10.1111/j.1945-5100.1991.tb01033.x· OSTI ID:5191692

Wasson, J T; Wang, Sichao ^[1]

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1. California, University, Los Angeles (USA) Purple Mountain Observatory, Nanjing (People's Republic of China)

Age patterns observed in meteorite groups reflect the different thermal or impact histories experienced by their parent bodies. To assess the number of ordinary chondrite (OC) parent bodies, rare-gas data in the Schultz and Kruse (1989) data base were used to calculate U, Th-He gas-retention ages. Most H- and LL-chondrite ages are high; about 81 percent are greater than 2.2 Ga. In contrast, most L-chondrite ages are low; about 69 percent are not greater than 2.2 Ga, and about 35 percent are not greater than 0.9 Ga. The latter fraction is substantially lower than the value of 44 percent given by Heymann (1967). The difference is attributed to the preferential inclusion of shocked L chondrites in early studies. Broad age peaks in the H and LL groups near 3.4 Ga probably reflect thermal loss during metamorphism, but in the H distribution there is a hint of minor outgassing 'events' near 1 Ga. The L/LL chondrites have chemical properties intermediate between and unresolvable from L and LL chondrites. The high ages of most L/LL chondrites are evidence against these originating on the L parent body; the L/LL age distribution is consistent with an origin on the LL parent body or on an independent body. 22 refs.

• OSTI ID: 5191692
• Journal Information: Meteoritics; (United States), Vol. 26; ISSN 0026-1114
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHONDRITES
ISOTOPE DATING
ORIGIN
CHEMICAL COMPOSITION
HELIUM
METAMORPHISM
SOLAR SYSTEM EVOLUTION
THORIUM
URANIUM
ACTINIDES
AGE ESTIMATION
ELEMENTS
FLUIDS
GASES
METALS
METEORITES
NONMETALS
RARE GASES
STONE METEORITES
640107* - Astrophysics & Cosmology- Planetary Phenomena