Age of a eucrite clast from the Bholghati howardite

Journal Article · Wed Aug 01 00:00:00 EDT 1990 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(90)90045-M· OSTI ID:6205388

Nyquist, L E; Bogard, D D; Morris, R M ^[1]; Wiesmann, H; Bansal, B M; Shih, C Y ^[2]

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1. NASA Johnson Space Center, Houston, TX (USA)
2. Lockheed Engineering and Sciences Co., Houston, TX (USA)

{sup 39}Ar-{sup 40}R, Rb-Sr, and Sm-Nd investigations of the large eucrite clast (,1) studied by the Bholghati Consortium show that it crystallized from a melt {approximately} 4.51 Ga ago. The crystallization age is given most precisely by a Sm-Nd internal isochron of 4.510 {plus minus} 0.034 Ga for {lambda}({sup 147}Sm) = 0.00654 (Ga){sup {minus}1}. {sup 142}Nd/{sup 144}Nd measurements show that the clast contained liver {sup 146}Sm at the time of crystallization. A solar system initial ({sup 146}Sm/{sup 144}Sm){sub 0} = 0.0043{sup +0.0039}{sub {minus}0.0026} at 4.555 Ga ago can be calculated from a {sup 146}Sm-{sup 142}Nd isochron and the age of the clast. Alternatively, using ({sup 146}Sm/{sup 144}Sm){sub 0} = 0.0045 as previously reported in the literature, a {sup 146}Sm-{sup 142}Nd formation interval of 0.05{sup +0.12}{sub {minus}0.08} Ga can be calculated, which is concordant with the {sup 147}Sm-{sup 143}Nd isochron age and in agreement with Pu-U-Xe and Pu-Nd-Xe formation intervals reported in a companion Consortium paper. The initial {sup 143}Nd/{sup 144}Nd (I{sub Nd}) of the clast was I{sub Nd} = 0.505958 {plus minus} 50, normalized to {sup 146}Nd/{sup 144}Nd = 0.724140 and is consistent with the CHUR reference value for evolution in a source having chondritic relative REE (rare earth element) abundances prior to magma generation. The age and isotopic systematics of the clast are consistent with those of other eucrites are support the widely held assumption of a common parent body for howardites and eucrites. The isotopic investigations of polymict eucrites and howardites point to a prolonged cratering record on the howardite-eucrite-diogenite (HED) parent body and suggest that it survived the cataclysm affecting the Moon {approximately} 3.8-4.0 Ga ago.

• OSTI ID: 6205388
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 54:8; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHONDRITES
GEOLOGIC HISTORY
ISOTOPE DATING
PETROCHEMISTRY
ARGON ISOTOPES
CRYSTALLIZATION
INCLUSIONS
ISOTOPE RATIO
MAGMA
MAGMATISM
NEODYMIUM ISOTOPES
PETROGENESIS
RUBIDIUM ISOTOPES
SAMARIUM ISOTOPES
STRONTIUM ISOTOPES
AGE ESTIMATION
ALKALI METAL ISOTOPES
ALKALINE EARTH ISOTOPES
ISOTOPES
METEORITES
PHASE TRANSFORMATIONS
RARE EARTH ISOTOPES
STONE METEORITES
580000* - Geosciences
640106 - Astrophysics & Cosmology- Cosmology