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dc.contributor.authorFernandes, V. A.
dc.contributor.authorBurgess, R.
dc.contributor.authorTurner, G.
dc.date.accessioned2021-02-12T20:56:08Z
dc.date.available2021-02-12T20:56:08Z
dc.date.issued2003-01-01
dc.identifier.citationFernandes, V. A., Burgess, R., & Turner, G. (2003). 40Ar‐39Ar chronology of lunar meteorites Northwest Africa 032 and 773. Meteoritics & Planetary Science, 38(4), 555-564.
dc.identifier.issn1945-5100
dc.identifier.doi10.1111/j.1945-5100.2003.tb00026.x
dc.identifier.urihttp://hdl.handle.net/10150/655681
dc.description.abstractThe 40Ar-39Ar dating technique has been applied to the lunar meteorites Northwest Africa 032 (NWA 032), an unbrecciated mare basalt, and Northwest Africa 773 (NWA 773), (composed of cumulate and breccia lithologies), to determine the crystallization age and timing of shock events these meteorites may have experienced. Stepped heating analyses of several different samples of NWA 032 gave complex age spectra but indistinguishable total ages with a mean of 2.779 +/- 0.014 Gyr. Possible causes of the complex age spectra obtained from NWA 032 include recoil of 39Ar, or the presence of pre-shock 40Ar incorporated into shock-melt veins. The effects of shock veins were investigated by laser fusion of 20 small samples expected to contain varying proportions of the shock veins. The laser ages show a narrow age distribution between 2.61-2.86 Gyr and a mean of 2.73 +/- 0.03 Gyr, identical to the total age of ~2.80 Gyr obtained for the bulk sample. Diffusion calculations based on the stepped heating data indicate that Ar release can be reconciled by release from feldspar (and possibly shock veins) at low temperatures followed by pyroxene at higher temperatures. The exposure age of NWA 032 is 212 +/- 11 Myr, and it contains low trapped solar Ar. Stepped heating of cumulate and breccia portions of NWA 773 also give a relatively young age of 2.91 Gyr. The presence of trapped Ar in the breccia makes the age determination of this component less precise, but release of Ar appears to be from the same mineral phase, assumed to be plagioclase, in both lithologies. A marked difference in exposure age between the 2 lithologies also exists, with the breccia having spent 81 Myr longer at the lunar surface; this finding is consistent with the higher trapped Ar content of this lithology. Assuming that 2.80 Gyr and 2.91 Gyr are the crystallization ages of NWA 032 and NWA 773 respectively, these two meteorites are the youngest lunar mare basalts available for study.
dc.language.isoen
dc.publisherThe Meteoritical Society
dc.relation.urlhttps://meteoritical.org/
dc.rightsCopyright © The Meteoritical Society
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectNWA 773
dc.subjectNWA 032
dc.subjectMare meteorites
dc.subject40Ar-39Ar dating
dc.subjectlunar volcanism
dc.title40Ar-39Ar chronology of lunar meteorites Northwest Africa 032 and 773
dc.typeArticle
dc.typetext
dc.identifier.journalMeteoritics & Planetary Science
dc.description.collectioninformationThe Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information.
dc.eprint.versionFinal published version
dc.description.admin-noteMigrated from OJS platform February 2021
dc.source.volume38
dc.source.issue4
dc.source.beginpage555
dc.source.endpage564
refterms.dateFOA2021-02-12T20:56:08Z


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