Demonstration of REE fractionation among individual chondrules from the allende (CV3) chondrite
- Kobe Univ. (Japan)
Abundances of REE, Ba, Sr, Rb, K, Mg and Ca were determined by precise mass spectrometric isotope dilution techniques for 24 chondrules from the Allende (CV3) chondrite. The REE abundances are 2.5-10 {times} CI for barred olivine chondrules, 2-8 {times} CI for porphyritic and nonporphyritic pyroxene chondrules, 0.15-4 {times} CI for porphyritic olivine and porphyritic olivine-pyroxene chondrules and are more or less similarly fractionated. General REE fractionations and large (up to 170%) anomalies of Ce, Eu and Yb occur in all chondrule types, particularly for barred olivine and pyroxene-rich chondrules. Positive correlations of REE with the moderately volatile elements, K and Rb, as well as other refractory elements, Ca, Sr and Ba, are independent of textural type and major chemical compositions. Each type of chondrule has large and systematic abundance variations of K and Rb, but shows a constant K/Rb ratio close to that of CIs. From the these results, the following constraints on the chemical characteristics of precursors and chondrule-forming events are suggested: (1) vaporization loss of alkalis accompanied by K/Rb fractionation did not occur during chondrule-formation melting events, (2) elemental abundances were basically established prior to melting events by accretion of alkali-free component(s) and alkali-bearing refractory precursors with fractionated REE, (3) gas/solid (or liquid) processes yielding REE fractionations took place during the formation of refractory precursors.
- OSTI ID:
- 5557689
- Journal Information:
- Geochimica et Cosmochimica Acta; (USA), Vol. 52:6; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHONDRITES
INCLUSIONS
CHEMICAL COMPOSITION
RARE EARTHS
FRACTIONATION
ANTARCTICA
BARIUM
CALCIUM
GEOCHEMISTRY
MAGNESIUM
MASS SPECTROSCOPY
OLIVINE
POTASSIUM
RUBIDIUM
STRONTIUM
ALKALI METALS
ALKALINE EARTH METAL COMPOUNDS
ALKALINE EARTH METALS
ANTARCTIC REGIONS
CHEMISTRY
ELEMENTS
IRON COMPOUNDS
IRON SILICATES
MAGNESIUM COMPOUNDS
MAGNESIUM SILICATES
METALS
METEORITES
MINERALS
OXYGEN COMPOUNDS
POLAR REGIONS
SEPARATION PROCESSES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SPECTROSCOPY
STONE METEORITES
TRANSITION ELEMENT COMPOUNDS
580400* - Geochemistry- (-1989)