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Ar-40/Ar-39 age spectra of Apollo 15 impact melt rocks by laser step-heating and their bearing on the history of lunar basin formationResults are reported on 26 high-resolution (16-51 steps) Ar-40/Ar-39 age spectra obtained on 12 Apollo-15 melt rocks of different composition using a continuous laser system on submg fragments of recrystallized melt and single-crystal plagioclase clasts from impact melt rocks collected at the Apennine Front where the Imbrium and Serenitatis basins intersect. A table is presented with the summary of the Ar-40/Ar-39 spectrum data, which represent 891 individual temperature step analyses. Also presented are 20 of the 26 age spectra along with their respective K/Ca plots. Melt rock fragments and plagioclase clasts from seven of the 12 samples analyzed yielded reproducible, intermediate-T Ar-40/Ar-39 age spectrum plateaus, which were interpreted as crystallization ages that represent the times of impact of bolides onto the lunar surface.
Document ID
19930069764
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Dalrymple, G. B.
(USGS Menlo Park, CA, United States)
Ryder, Graham
(Lunar and Planetary Inst. Houston, TX, United States)
Date Acquired
August 16, 2013
Publication Date
July 25, 1993
Publication Information
Publication: Journal of Geophysical Research
Volume: 98
Issue: E7
ISSN: 0148-0227
Subject Category
Lunar And Planetary Exploration
Accession Number
93A53761
Funding Number(s)
CONTRACT_GRANT: NASW-4066
Distribution Limits
Public
Copyright
Other

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