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Neutron capture effects in lunar gadolinium and the irradiation histories of some lunar rocks.The Gd isotopic composition in 19 lunar rock and soil samples from three Apollo sites is reported. The analytical techniques and the high precision mass spectrometric measurements are discussed. Enrichments in the Gd-158 oxide to G-157 oxide ratio due to neutron capture range up to 0.75%. Integrated 'thermal' neutron fluxes derived from the isotopic anomalies of Gd are compared with spallation Kr data from aliquot samples to construct a model which gives both average cosmic-ray irradiation depths and effective neutron exposure ages for some rocks. Rock 14310 is the first lunar sample where Kr anomalies due to resonance neutron capture in Br are observed. A Kr-81/Kr exposure age of 262 (plus or minus 7)m.y. is calculated for this rock.
Document ID
19720040488
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Lugmair, G. W.
Marti, K.
(California, University La Jolla, Calif., United States)
Date Acquired
August 6, 2013
Publication Date
December 1, 1971
Publication Information
Publication: Earth and Planetary Science Letters
Volume: 13
Issue: 1, De
Subject Category
Space Sciences
Accession Number
72A24154
Distribution Limits
Public
Copyright
Other

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