Gas-Retention and Cosmic-Ray Exposure Ages of Lunar Rock 15555

The last lava flow in the Hadley Rille area of Mare Imbrium, as inferred from an argon-40-argon-39 experiment on a plagioclase separate from the lunar basalt 15555, occurred 3.31 ± 0.03 × 10$^{9}$ years ago. An argon-40-argon-39 experiment on a whole rock sample shows significant loss of radiogenic...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 1972-01, Vol.175 (4020), p.423-425
Main Authors: Podosek, F. A., Huneke, J. C., Wasserburg, G. J.
Format: Article
Language:English
Subjects:
Decay constants
Earth
Fluence
Lava flows
Lunar rocks
Neutrons
Plagioclase
Plateaus
Pyroxenes
Rocks
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Summary:The last lava flow in the Hadley Rille area of Mare Imbrium, as inferred from an argon-40-argon-39 experiment on a plagioclase separate from the lunar basalt 15555, occurred 3.31 ± 0.03 × 10$^{9}$ years ago. An argon-40-argon-39 experiment on a whole rock sample shows significant loss of radiogenic argon-40 and yields a well-defined, high-temperature plateau indicating a lower age of 3.22 ± 0.03 × 10$^{9}$ years. A cosmic-ray exposure age of 90 ± 10 × 10$^{6}$ years is determined from the ratio of spallogenic argon-38 to calcium.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.175.4020.423