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dc.contributor.authorNorman, M. D.
dc.contributor.authorBorg, L. E.
dc.contributor.authorNyquist, L. E.
dc.contributor.authorBogard, D. D.
dc.date.accessioned2021-02-12T20:56:09Z
dc.date.available2021-02-12T20:56:09Z
dc.date.issued2003-01-01
dc.identifier.citationNorman, M. D., Borg, L. E., Nyquist, L. E., & Bogard, D. D. (2003). Chronology, geochemistry, and petrology of a ferroan noritic anorthosite clast from Descartes breccia 67215: Clues to the age, origin, structure, and impact history of the lunar crust. Meteoritics & Planetary Science, 38(4), 645-661.
dc.identifier.issn1945-5100
dc.identifier.doi10.1111/j.1945-5100.2003.tb00031.x
dc.identifier.urihttp://hdl.handle.net/10150/655686
dc.description.abstractThe petrology, major and trace element geochemistry, and Nd-Ar-Sr isotopic compositions of a ferroan noritic anorthosite clast from lunar breccia 67215 have been studied in order to improve our understanding of the composition, age, structure, and impact history of the lunar crust. The clast (designated 67215c) has an unusually well preserved igneous texture. Mineral compositions are consistent with classification of 67215c as a member of the ferroan anorthositic suite of lunar highlands rocks, but the texture and mineralogy show that it cooled more rapidly and at shallower depths than did more typical ferroan anorthosites (FANs). Incompatible trace element concentrations are enriched in 67215c relative to typical FANs, but diagnostic signatures such as Ti/Sm, Sc/Sm, plagiophile element ratios, and the lack of Zr/Hf and Nb/Ta fractionation show that this cannot be due to the addition of KREEP. Alternatively, 67215c may contain a greater fraction of trapped liquid than is commonly present in lunar FANs. 147Sm-143Nd isotopic compositions of mineral separates from 67215c define an isochron age of 4.40 +/- 0.11 Gyr with a near-chondritic initial 143Nd of +0.85 +/- 0.53. The 40Ar-39Ar composition of plagioclase from this clast records a post-crystallization thermal event at 3.93 +/- 0.08 Gyr, with the greatest contribution to the uncertainty in this age deriving from a poorly constrained correction for lunar atmosphere 40Ar. Rb-Sr isotopic compositions are disturbed, probably by the same event recorded by the Ar isotopic compositions. Trace element compositions of FANs are consistent with crystallization from a moderately evolved magma ocean and do not support a highly depleted source composition such as that implied by the positive initial 143Nd of the ferroan noritic anorthosite 62236. Alternatively, the Nd isotopic systematics of lunar FANs may have been subject to variable degrees of modification by impact metamorphism, with the plagioclase fraction being more strongly affected than the mafic phases. 147Sm-143Nd isotopic compositions of mafic fractions from the 4 ferroan noritic anorthosites for which isotopic data exist (60025, 62236, 67016c, 67215c) define an age of 4.46 +/- 0.04 Gyr, which may provide a robust estimate for the crystallization age of lunar ferroan anorthosites.
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.subjectanorthosite clast
dc.subjectisotopic compositions
dc.subjectpetrology
dc.subjecttrace elements
dc.subjectgeochemistry
dc.titleChronology, geochemistry, and petrology of a ferroan noritic anorthosite clast from Descartes breccia 67215: Clues to the age, origin, structure, and impact history of the lunar crust
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.beginpage645
dc.source.endpage661
refterms.dateFOA2021-02-12T20:56:09Z


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