Rare earth element carriers in the Shergotty meteorite and implications for its chronology

Journal Article · Mon Aug 01 04:00:00 EDT 1988 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(88)90194-9· OSTI ID:7266030

Lundberg, L L; Crozaz, G; Zinner, E ^[1]; McKay, G ^[2]

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1. Washington Univ., St. Louis, MO (USA)
2. NASA, Johnson Space Center, Houston, TX (USA)

Ion probe measurements of the rare earth element (REE) concentrations of individual grains of the Shergotty meteorite are reported. Phases analyzed include whitlockite, apatite, baddeleyite, augite, pigeonite, maskelynite and K-rich glass. U concentrations of whitlockite and apatite crystals were also obtained. The whole rock REE pattern is dominated by whitlockite, which contains over 95% of the light rare earth elements (LREE). REE concentrations in apatite are much lower than estimated by Laul et al. (1986). All of the whitlockites have the same relative abundances of LREE. The observation, by Jones et al. (1985), of a skeletal whitlockite with LREE enrichment is not confirmed by analyses of the same grain. Pyroxene rims are not enriched in LREE. No leachable carrier, enriched in LREE and associated with pyroxene, has been found. Instead, either a laboratory contamination or a petrographically cryptic phase such as a film on grain boundaries is suspected as the carrier of LREE enrichments. Estimates of REE abundances in the Shergotty intercumulus melt indicate that a complex petrogenesis is required, in agreement with the conclusions of McKay et al. (1986a). Pyroxene distribution coefficients measured experimentally are compared with estimates from measured REE abundances in augite and pigeonite. Evolution of REE abundances in the Shergotty late-stage interstitial melt, as inferred from analyses of whitlockite, conforms with trends predicted from partitioning considerations, and requires no special processes such as metasomatism. The average U concentrations of whitlockite and apatite are respectively 540 and 1,550 ppb. Although the calcium phosphates are enriched in U, they contain less than 20% of the U in Shergotty.

• OSTI ID: 7266030
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 52:8; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
640106 -- Astrophysics & Cosmology-- Cosmology
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACTINIDES
AGE ESTIMATION
APATITES
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMISTRY
ELEMENTS
GEOCHEMISTRY
GEOLOGY
ION MICROPROBE ANALYSIS
ISOTOPE DATING
ISOTOPE RATIO
ISOTOPES
METALS
METEORITES
MICROANALYSIS
MINERALOGY
MINERALS
NEODYMIUM ISOTOPES
NONDESTRUCTIVE ANALYSIS
OXYGEN COMPOUNDS
PETROGENESIS
PETROLOGY
PHOSPHATE MINERALS
PYROXENES
RARE EARTH ISOTOPES
RARE EARTHS
SAMARIUM ISOTOPES
SILICATES
SILICON COMPOUNDS
URANIUM