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dc.contributor.advisorLin, Jung-Fuen
dc.creatorLu, Changen
dc.date.accessioned2012-07-20T17:45:34Zen
dc.date.available2012-07-20T17:45:34Zen
dc.date.issued2012-05en
dc.date.submittedMay 2012en
dc.identifier.urihttp://hdl.handle.net/2152/ETD-UT-2012-05-5456en
dc.descriptiontexten
dc.description.abstractElastic properties of the major constituent minerals in the Earth’s upper mantle at relevant high pressure-temperature (P-T) conditions are crucial for understanding the composition and seismic velocity structures of the region. In this study, we have measured the single-crystal elasticity of natural Fe-bearing pyrope, Mg2.04Fe0.74Ca0.16Mn0.05Al2Si3O12, using in situ Brillouin spectroscopy and X-ray diffraction at simultaneous high P-T conditions up to 20 GPa and 750 K in an externally-heated diamond anvil cell. The derived aggregate adiabatic bulk and shear modulus (KS0, G0) at ambient conditions are 168.2 (±1.8) GPa and 92.1 (±1.1) GPa, respectively, consistent with literature results. Using the third-order Eulerian finite-strain equation to fit the high P-T data, the derived pressure derivative of the bulk and shear moduli at constant temperature are (∂KS/∂P)T=4.4 (±0.1) and (∂G/∂P)T=1.2 (±0.1), respectively. Applying these pressure derivatives, the temperature derivative of these moduli at constant pressure are also calculated, yielding (∂KS/∂T)P=-18.5(±1.3) MPa/K and (∂G/∂T)P=-5.2(±1.1) MPa/K, respectively. Compared to literature values, our results show that addition of 25% Fe in pyrope increases the pressure derivative of the bulk modulus by 7%, but has a negligible effect on other elastic parameters. Extrapolation of our results shows that Fe-bearing pyrope remains almost elastically isotropic at relevant P-T conditions of the upper mantle, indicating that it may not have a significant contribution to seismic Vp and Vs anisotropy in the upper mantle. Together with the elasticity of olivine and pyroxene minerals in the upper mantle, we have constructed new velocity profiles for two representative compositional models, pyrolite and piclogite, along Earth’s upper mantle geotherm. These velocity models show Vs profiles consistent with seismic observations, although Vp profiles are slightly lower than in seismic models.en
dc.format.mimetypeapplication/pdfen
dc.language.isoengen
dc.subjectHigh pressureen
dc.subjectHigh temperatureen
dc.subjectDiamond anvil cellen
dc.subjectMineral physicsen
dc.subjectUpper mantleen
dc.subjectGarneten
dc.subjectBrillouin spectroscopyen
dc.subjectIron-bearing pyropeen
dc.titleElasticity of single-crystal iron-bearing pyrope to 20 GPa and 750 Ken
dc.date.updated2012-07-20T17:45:44Zen
dc.identifier.slug2152/ETD-UT-2012-05-5456en
dc.contributor.committeeMemberGrand, Stephen P.en
dc.contributor.committeeMemberLassiter, John C.en
dc.description.departmentGeological Sciencesen
dc.type.genrethesisen
thesis.degree.departmentGeological Sciencesen
thesis.degree.disciplineGeological Sciencesen
thesis.degree.grantorUniversity of Texas at Austinen
thesis.degree.levelMastersen
thesis.degree.nameMaster of Science in Geological Sciencesen


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