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dc.contributor.authorEdmunson, J.
dc.contributor.authorBorg, L. E.
dc.contributor.authorShearer, C. K.
dc.contributor.authorPapike, J. J.
dc.date.accessioned2021-02-12T21:17:39Z
dc.date.available2021-02-12T21:17:39Z
dc.date.issued2005-01-01
dc.identifier.citationEdmunson, J., Borg, L. E., Shearer, C. K., & Papike, J. J. (2005). Defining the mechanisms that disturb the Sm‐Nd isotopic systematics of the Martian meteorites: Examples from Dar al Gani 476 and Allan Hills 77005. Meteoritics & Planetary Science, 40(8), 1159-1174.
dc.identifier.issn1945-5100
dc.identifier.doi10.1111/j.1945-5100.2005.tb00181.x
dc.identifier.urihttp://hdl.handle.net/10150/656029
dc.description.abstractMicrobeam studies of Martian meteorites Dar al Gani (DaG) 476 and Allan Hills (ALH) 77005 have been conducted to identify potential causes of disequilibrium exhibited in their Sm-Nd isotopic systematics. Olivine and maskelynite mineral fractions on the DaG 476 isochron are displaced relative to their positions as dictated by measured mineral compositions. The olivine mineral fractions from ALH 77005 not only have a relatively low Sm/Nd ratio, but appear to contain an unradiogenic component that shifts the olivine mineral fraction off the isochron defined by the pyroxene and maskelynite mineral fractions. Trace components such as melt inclusions, impact melt, high-Si mesostasis, and altered olivine were analyzed using scanning electron microscopy, quantitative electron microscopy, and secondary ion mass spectrometry to determine their potential for disturbing the isotopic systematics of the mineral fractions, assuming that the mineral fractions were not completely pure. Mixing models indicate that the presence of melt inclusions in the DaG 476 olivine mineral fraction lowered its Sm/Nd ratio. The maskelynite mineral fraction contains a related but more evolved mesostasis component that raised the Sm/Nd ratio of the fraction. The position of two olivine mineral fractions below the ALH 77005 isochron is interpreted to reflect small additions of impact melt with a light rare earth element enriched pattern and a non-indigenous, unradiogenic Nd component. Furthermore, the presence of rare earth elements in olivine and maskelynite from both igneous and non-igneous components such as melt inclusions, mesostasis, and impact melt is observed on a fine (<30 m)icrometers scale. Despite the addition of this material, the Sm-Nd ages are not affected. This study demonstrates that detailed mineral separation procedures as employed by modern geochronology laboratories permit reliable ages to be derived from shocked and altered samples.
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.subjectAllan Hills 77005
dc.subjectIsotopic disturbance
dc.subjectSm-Nd isotopes
dc.subjectMartian meteorites
dc.titleDefining the mechanisms that disturb the Sm-Nd isotopic systematics of the Martian meteorites: Examples from Dar al Gani 476 and Allan Hills 77005
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.volume40
dc.source.issue8
dc.source.beginpage1159
dc.source.endpage1174
refterms.dateFOA2021-02-12T21:17:39Z


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