The isotopic composition of Gd and the neutron capture effects in samples from Apollo 11
Abstract
The isotopic composition of Gd in six rocks, one breccia, two core samples, and soil has been determined. Isotopic variations due to capture of low energy neutrons produced by cosmic ray interactions have been found in all samples except for two rocks. Using cosmic ray exposure ages, the effective thermal neutron fluxes were calculated using a nominal value of ¹⁵⁷σ = 2.62 × 10⁵ barns. They vary from less than 0.27 n/cm² sec to 1.1 n/cm² inidicating variable shielding for the samples studied. The neutron dosage of the top and the bottom of core #2 is the same. This means that the soil has been mixed to 13 cm at least once in the last 100 my. A mixing depth of 23 to 47 m can be calculated based on the integrated effective thermal neutron dosage of 9 × 10¹⁵ n/cm² for the soil and an assumed surface flux of 0.2 n/cm² sec. For rock #17 the barium isotopic composition was determined and found to be the same as terrestrial to within 0.1% for the five abundant isotopes.
Additional Information
© 1970 North-Holland Publishing Company. Published by Elsevier B.V. Received 18 February 1970. We thank H. Derksen and U. Derksen for their assistance with the chemical and mass spectrometric analyses. We have profited greatly from the frequent aid generously offered by D.A. Papanastassiou and his willingness to discuss problems in mass spectrometry. Discussions with R.E. Lingenfelter, J.C. Huneke, and F.A. Podosek have been of great benefit. Comments by A. Turkevich and J. Geiss were of great value. This work was supported by NASA contract NAS 9-8074. The mass spectrometric facilities used in this work were developed under NSF grant GP 9114.Additional details
- Eprint ID
- 115664
- Resolver ID
- CaltechAUTHORS:20220718-449423900
- NAS 9-8074
- NASA
- GP 9114
- NSF
- Created
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2022-07-20Created from EPrint's datestamp field
- Updated
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2022-07-20Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences
- Other Numbering System Name
- Caltech Division of Geological Sciences
- Other Numbering System Identifier
- 1716