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Nitrogen and light noble gases in ShergottyTwo samples of Shergotty and a sample of EETA 79001's lithology A have been analyzed for N, He, Ne, and Ar abundances and isotopic composition. After correcting for spallogenic nitrogen, the nitrogen isotopic ratios were found to be close to that of the terrestrial atmosphere. The spallogenic noble gas data are consistent with cosmic ray irradiation of both Shergotty and EETA 79001 at shallow shielding depths. Cosmic ray exposure ages were estimated to be in the range of 0.5-0.8 Myr for EETA 79001, and of 2.0-5.2 Myr for Shergotty, depending on the choice of object size and shielding. Among the two Shergotty samples, the contents of Ar-40 differed by a factor of 3. This difference can be attributed to either a small-scale mineralogical inhomogeneity or a significant variation in the degree of degassing of minerals during shock, although the presence of trapped argon with a high Ar-40/Ar-36 ratio and its heterogeneous distribution cannot be ruled out.
Document ID
19860063598
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Becker, R. H.
(Minnesota Univ. Minneapolis, MN, United States)
Pepin, R. O.
(Minnesota, University Minneapolis, United States)
Date Acquired
August 12, 2013
Publication Date
June 1, 1986
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 50
ISSN: 0016-7037
Subject Category
Lunar And Planetary Exploration
Accession Number
86A48336
Funding Number(s)
CONTRACT_GRANT: NAG9-60
Distribution Limits
Public
Copyright
Other

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