The influence of quartz textures on the seismic anisotropy in lower crustal granulites

Braun, Günter, Siegesmund, Siegfried and Dahms, Michael (1991) The influence of quartz textures on the seismic anisotropy in lower crustal granulites Journal of Structural Geology, 13 (8). pp. 955-966. DOI 10.1016/0191-8141(91)90090-6.

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Abstract

Analyses that are based on the spherical harmonic representation of the orientation distribution function (ODF) which can describe the three-dimensional nature of textures, can be used to evaluate the effective elastic response of quartz in polycrystalline aggregates and to account for the dependence of crystal and sample symmetries. The aggregate elastic constants are determined using the Voigt method by averaging overall orientations weighted by the ODF. The application of the results is given for three different, commonly observed, quartz textures. The directional dependence of the seismic wave velocities (VP and shear wave splitting) that are calculated by ODF using the texture pole figures can also be shown using the respective single crystal velocities. The experimental seismic data at 400 MPa for a muscovite-bearing quartzite where most of the cracks are closed are in good agreement with the calculated velocity anisotropies (Voigt average) that are based on volume percentages of major minerals, the stiffness tensors of rock-forming minerals and the measured crystallographic orientation. The combination of the calculated elastic constants from different quartz textures together with plagioclase, muscovite, orthoclase, garnet and sillimanite explain the texture-related directional dependence of VP, VS and VSS in lower crustal granulites. The results suggest that the directional variation of wave velocities of quartz-rich granulites do not provide the necessary impedance contrast that gives rise to strong seismic reflections.

Document Type: Article
Research affiliation: Kiel University
Refereed: No
DOI etc.: 10.1016/0191-8141(91)90090-6
ISSN: 0191-8141
Date Deposited: 02 Feb 2012 09:28
Last Modified: 08 Oct 2012 07:33
URI: http://eprints.uni-kiel.de/id/eprint/15504

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