New approach to quantification of metamorphism using ultra-small and small angle neutron scattering

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dc.contributor.authorAnovitz, LMen_AU
dc.contributor.authorLynn, GWen_AU
dc.contributor.authorCole, DRen_AU
dc.contributor.authorRother, Gen_AU
dc.contributor.authorAllard, LFen_AU
dc.contributor.authorHamilton, WAen_AU
dc.contributor.authorPorcar, Len_AU
dc.contributor.authorKim, MHen_AU
dc.date.accessioned2009-10-07T02:16:20Zen_AU
dc.date.accessioned2010-04-30T04:56:57Zen_AU
dc.date.available2009-10-07T02:16:20Zen_AU
dc.date.available2010-04-30T04:56:57Zen_AU
dc.date.issued2008-07en_AU
dc.date.statistics2008-07en_AU
dc.description.abstractSmall- and Ultra-Small Angle Neutron Scattering (SANS and USANS) provide powerful tools for analysis of porous rocks because neutrons probe both the surface and the interior of the material providing bulk statistical information over a wide range of length scales. For monomineralic materials scattering contrast arises from the difference between the scattering length density of the rock and the pores (taken to be zero). Pore-grain interfaces are best described by self-similar fractals with non-universal dimensions (2 < D < 3). This leads to a non-integer power-law as a function of the scattering I(Q) = I(1)Q-a + B where B is the incoherent background. For a volume or mass fractal scatterer a = D; if only the surface is a fractal, then a = 6-D. In this manner, surface fractals (a>3) and mass fractals (a<3) are easily distinguished. Non-fractal “fuzzy” interfaces (a>4) may also be observed. We have used SANS and USANS to characterize samples from two transects (contact out to ~1700 m) from the contact metamorphosed Hueco limestone at Marble Canyon, TX. Significant changes in a number of scattering parameters are observed as a function of distance, including regions of the aureole outside the range of classic reaction petrology. Our modeling suggests that changes in surface free energy, pore volume and hydrogen content, among other variables, can be quantified. Both the mass and surface fractals Dm and Ds can be fitted as a function of the surface fractal correlation length as: log10(D/r) = -0.9648 * log10r(Å) + 0.30103 r2 = 0.9999, s = 0.038 although metamorphism does not necessarily proceed linearly along this curve with increasing grade. Nonetheless, the ability to measure these variables shows that these techniques provide a novel approach to the analysis and study of metamorphism.en_AU
dc.description.sponsorshipGeochemical Society; European Association of Geochemistry.en_AU
dc.identifier.citationAnovitzi, L. M., Lynn, G. W., Cole, D. R., Rother, G., Allard, L. F., & Hamilton, W. A., Porcar, L., & Kim, M. H. (2008). New approach to quantification of metamorphism using ultra-small and small angle neutron scattering. 18th Annual V.M. Goldschmidt Conference (Goldschmidt 2008) - "from Sea to Sky", 13th - 18th July 2008. Vancouver, Canada: University of British Columbia. In Geochimica et Cosmochimica Acta, 72(12), A28. doi:10.1016/j.gca.2008.05.004en_AU
dc.identifier.conferenceenddate18 July 2008en_AU
dc.identifier.conferencename18th Annual V.M. Goldschmidt Conference (Goldschmidt 2008) - 'from Sea to Sky'en_AU
dc.identifier.conferenceplaceVancouver, Canadaen_AU
dc.identifier.conferencestartdate13 July 2008en_AU
dc.identifier.govdoc1032en_AU
dc.identifier.issn0016-7037en_AU
dc.identifier.issue12en_AU
dc.identifier.journaltitleGeochimica et Cosmochimica Actaen_AU
dc.identifier.paginationA28en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/1949en_AU
dc.identifier.urihttp://dx.doi.org/10.1016/j.gca.2008.05.004en_AU
dc.identifier.volume72en_AU
dc.language.isoenen_AU
dc.publisherElsevier; Cambridge Publicationsen_AU
dc.subjectSmall angle scatteringen_AU
dc.subjectMetamorphismen_AU
dc.subjectPorous materialsen_AU
dc.subjectRocksen_AU
dc.subjectNeutronsen_AU
dc.subjectScattering lengthsen_AU
dc.titleNew approach to quantification of metamorphism using ultra-small and small angle neutron scatteringen_AU
dc.typeConference Abstracten_AU
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