Structural Analysis of Deformation Texture Crustal and Upper Mamtle Materials and Rheology of the Earth

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We analyzed texture of a peridotite sample, and investigated deformation process in the upper mantle. The peridotite sample shows P-wave velocity anisotropy of 7-8 % due to preferred orientation of olivine. In order to determine distribution of grain size, area S, perimeter P and aspect ratio of olivine in peridotite, more than 2000 grains are statistically analyzed. Average values (and standard deviations) of aspect ratio, roundness and mean diameter are I..83 (0.48), 0.66 (0.58) and 59.1 (52.7) mum, respectively. Histograms of the particle parameters generally fit to the Gamma distribution function. Correlation between particle parameters is observed ; e.g., perimeter is proportional to area as P^<alpha> S^<0.54>. The shapes of olivine grains are self-similar, and the fractal dimension is about 1.1. Further, fabric analysis of olivine shows that large relict grains are oriented against their slip systems and are not subject to deformation. However, small grains are recrystallized because their orientation is not against the slip systems. As such, grain size depends on lattice orientation of olivine.We also analyzed deformation texture of a limestone. Particle parameters were determined for the thin sections parallel (XY-plane) and perpendicular (XZ-plane) to the foliation. Lineation is clear in the XZ-plane ; however, no lineation is observed and calcite is equi-granular in the XY-plane. In fact, we obtain average aspect ratio and roundness of 1.91 and 0.55, respectively, for the XZ-plane, and of 1.68 and 0.57 for the XY-plane.