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dc.contributor.authorBland, P. A.
dc.contributor.authorCressey, G.
dc.contributor.authorMenzies, O. N.
dc.date.accessioned2021-02-12T20:56:29Z
dc.date.available2021-02-12T20:56:29Z
dc.date.issued2004-01-01
dc.identifier.citationBland, P. A., Cressey, G., & Menzies, O. N. (2004). Modal mineralogy of carbonaceous chondrites by X‐ray diffraction and Mössbauer spectroscopy. Meteoritics & Planetary Science, 39(1), 3-16.
dc.identifier.issn1945-5100
dc.identifier.doi10.1111/j.1945-5100.2004.tb00046.x
dc.identifier.urihttp://hdl.handle.net/10150/655783
dc.description.abstractCarbonaceous chondrites are among the most analyzed geological materials on Earth. However, despite this attention, and unlike most terrestrial rocks, little is known on the abundance of individual phases within them. Here, we show how a combination of several novel X-ray diffraction (XRD) techniques (including a high-brightness X-ray MicroSource(R)), and Mössbauer spectroscopy, allows a complete modal mineralogy to be ascertained from even the most highly unequilibrated, fine-grained chondrites for all minerals of abundance >1 wt%. Knowledge of the modal mineralogy of a sample also allows us to calculate grain density. We analyzed Allende, Murchison, Tagish Lake, and Orgueil. Based on our modal data, the grain density estimates for Allende, Murchison, and Orgueil are close to literature values. In the case of Tagish Lake, there is no published grain density, although a bulk density measurement does exist. Taking our estimate of grain density, and the measured bulk density, we calculate an exceptionally high porosity of 41% for this meteorite, similar to some chondritic IDPs and in line with a porosity calculated from an entry model for the Tagish Lake fireball. Although it is an oxidized CV, magnetite is present in Allende at a level of <0.5 wt% or <0.3 vol%, a result that is substantiated by several other instrumental studies. This may be an oxidized meteorite, but that oxidation is not manifested in abundant magnetite. In addition, we note appreciable fayalitic olivine in Orgueil, detected by both XRD and Mössbauer. We employed MicroSource(R) XRD to look at heterogeneity in mineral abundance in Orgueil and found substantial variation, with phyllosilicates varying inversely with olivine. The data suggest that Orgueil was initially composed primarily of anhydrous materials, which have been partially, but not completely, altered. Although the data are preliminary, comparison between our XRD modal assessment, bulk chemistry, grain density, and Mössbauer data, suggests that our estimates of mineral abundance are robust. The advent of MicroSource(R) XRD allows similar modal data to be acquired from samples as small as a few hundred micrograms.
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.subjectcarbonaceous chondrites
dc.subjectMössbauer spectroscopy
dc.subjectModal mineralogy
dc.titleModal mineralogy of carbonaceous chondrites by X-ray diffraction and Mössbauer spectroscopy
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.volume39
dc.source.issue1
dc.source.beginpage3
dc.source.endpage16
refterms.dateFOA2021-02-12T20:56:29Z


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