Laser-microprobe studies of rare gas isotopes in meteorites

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6753337

Kirschbaum, C L

A new rare gas mass spectrometer of high sensitivity coupled to a laser microprobe extraction system (constructed by the author) is described. The laser microprobe is applied to a long standing problem in cosmochemistry - determining the minerals which carry /sup 129/Xe from the decay of the extinct radioactive isotope /sup 129/I (this /sup 129/Xe is referred to as /sup 129/Xe/sub r/). The /sup 129/Xe/sub r//sup 127/I ratios and the inferred relative formation times of these minerals are also determined. In the Allende meteorite, sodalite (Na/sub 8/(Al/sub 6/Si/sub 6/O/sub 24/)Cl/sub 2/) has been verified to be the major carrier for /sup 129/Xe/sub r/ in fine-grained inclusions. Although the exact mineral phase responsible has not been identified a carrier other than sodalite is also present in matrix from Allende. The /sup 129/Xe/sub r/ of this carrier is physically correlated with trapped xenon in the matrix and has a chlorine/iodine ratio which is lower than the ratio in the fine-grained inclusions. The /sup 129/Xe/sub r///sup 127/I ratios for sodalite from the fine-grained inclusions, and matrix are similar - between 1.25 and 1.35 x 10/sup -4/. This implies an age for these samples within 2 million years of the Bjurbole meteorite (Bjurbole is commonly used as a standard for meteorite formation intervals). The /sup 129/Xe/sub r///sup 127/I ratio of the sample of the fine-grained inclusion in which sodalite was thermally decomposed by laboratory preheating, is 2.4 x 10/sup -4/ or 16 million years before Bjurbole. The alteration-product-free coarse-grained inclusion on the other hand showed a ratio of 3.15 x 10/sup -5/ or 35 million years after Bjurbole. These relative formation intervals are much longer than expected for nebular processes and hence are either due to parent body processes or heterogeneity of the /sup 129/I//sup 127/I ratio in the early solar system.

• Research Organization: California Univ., Berkeley (USA)
• OSTI ID: 6753337
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100 -- Geology & Hydrology-- (-1989)
580400* -- Geochemistry-- (-1989)
AGE ESTIMATION
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL ANALYSIS
CHEMISTRY
CHLORINE
DAYS LIVING RADIOISOTOPES
DESIGN
ELECTRON MICROPROBE ANALYSIS
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOCHEMISTRY
HALOGENS
INCLUSIONS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE
IODINE 127
IODINE 129
IODINE ISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPE RATIO
ISOTOPES
LASERS
MASS SPECTROSCOPY
METEORITES
MICROANALYSIS
MINERALS
NONMETALS
NUCLEI
ODD-EVEN NUCLEI
PERFORMANCE
RADIOISOTOPES
SPECTROSCOPY
STABLE ISOTOPES
XENON 129
XENON 131
XENON 132
XENON ISOTOPES
YEARS LIVING RADIOISOTOPES