| Description |
Synchrotron x-ray diffraction can be a useful tool in the study of fine grained materials. The highly focused, high energy beams combined with fast 2-dimensional detectors allow for the quantitative study of crystallographic preferred orientation (texture) of these difficult to study materials. Here, two different studies were done that demonstrate the range of applications for this technique. Shales display a large degree of seismic anisotropy, largely due to texturing of clay minerals. Eleven samples from the Green River and Mancos Shale formations were studied. P- and S-wave velocities were calculated based on orientation distributions obtained through Rietveld analysis. P-wave anisotropy was found to range from 0.4% to 7.1% in Green River samples, and from 1.8% to 7.6% in Mancos Shale samples. This is found to be similar to, but generally lower than, that of other shales previously studied around the world. This is due to lower average clay volume fractions in the Green River and Mancos samples studied here. The clay volume fraction and the intrinsic P-wave anisotropy in the samples studied here and in previous work show a linear correlation. The D" region of the lower mantle lies just above the core mantle boundary and exhibits complex seismic anisotropy. The post-perovskite phase of (Mg,Fe)SiO3 is thought to be one of the main mineral phases here, and it is possible that texturing (preferred orientation) of the mineral is responsible for a large portion of the seismic anisotropy observed in the D". Texture development in other post-perovskite structured compounds, including MgSiO3, MgGeO3, and CaIrO3, have been studied. In this thesis, a new experiment was done on the NaMgF3 post-perovskite analog in order to further the study of these compounds. NaMgF3 perovskite was found to develop a strong (100) texture. NaMgF3 post-perovskite, synthesized from the perovskite phase, was found to have an initial texture of (130) oriented at high angles to compression. Upon compression, a secondary maximum near (001) develops, consistent with a dominant slip on (001)[100]. |
