/sup 129/I//sup 127/I variations among enstatite chondrites

Journal Article · Thu Dec 31 23:00:00 EST 1987 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(88)90059-2· OSTI ID:6996766

Kennedy, B M; Hudson, B; Hohenberg, C M; Podosek, F A

This paper presents the /sup 129/I//sup 127/I composition for 11 different enstatite chondrites. There is a well-defined hiatus in iodine isotopic compositions separating the enstatite chondrites. The hiatus correlates with a similar hiatus defined by variations in chemical composition (both major and minor elements). EH(4,5) chondrites have /sup 129/I//sup 127/I ratios approx. 20% higher (approx. 4 m.y. older) than EL(6) chondrites. The enstatite chondrites are the third meteorite group, joining silicates in IAB irons and C3V carbonaceous chondrites, in which /sup 129/I//sup 127/I correlates with chemical composition. Within each enstatite chondrite group, the variations in initial iodine isotopic composition is less than approx. +/- 4%, comparable to the experimental resolution. The approx. 20% difference between EH and EL may indicate a maximum iodine isotopic heterogeneity between the EH and EL nebular reservoirs. Alternatively, if EH and EL chondrites evolved from a homogeneous iodine isotopic reservoir, then the EL group must have evolved approx. 4.0 m.y. longer than the EH group and either in an environment with a much lower I/Xe ratio than presently observed or one which was open to the loss of radiogenic /sup 129/Xe. The latter case may imply a nebular environment and would therefore be consistent with the open system evolution required to produce the chemical hiatus. The duration of subsequent evolution in the high I/Xe environment must have been less than or equal to 1 m.y. and probably represents thermal metamorphism in two different parent bodies.

• Research Organization: Washington Univ., St. Louis, MO (USA)
• OSTI ID: 6996766
• Journal Information: Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 52:1; ISSN GCACA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMISTRY
CHONDRITES
COSMOCHEMISTRY
ENSTATITE
GEOCHEMISTRY
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE 127
IODINE 129
IODINE ISOTOPES
ISOTOPE RATIO
ISOTOPES
MAGNESIUM COMPOUNDS
MAGNESIUM SILICATES
METEORITES
MINERALOGY
MINERALS
NUCLEI
ODD-EVEN NUCLEI
OXYGEN COMPOUNDS
PYROXENES
QUANTITATIVE CHEMICAL ANALYSIS
RADIOISOTOPES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
STABLE ISOTOPES
STONE METEORITES
VARIATIONS
YEARS LIVING RADIOISOTOPES