THIN-SECTION SCALE SPATIAL VARIATION IN CRYSTALLOGRAPHIC PREFERRED ORIENTATION FABRICS

The proliferation of high-speed EBSD systems has made routine the analysis of crystallographic orientations from naturally and experimentally deformed rocks. One common sampling strategy for documenting crystallographic fabrics involves the mapping of full thin-sections (>1000 mm^2) at a coarse resolution. Alternatively, rapid improvements in analytical time have enabled high-resolution mapping of relatively small areas (1-10 mm^2) that provide a detailed view of the grain and subgrain structure. Consideration of these differing sampling strategies raises questions about the length-scales of texture variability within a sample. What is the minimum area relative to the grain-size that must be measured to observe a quantitatively representative texture distribution? Do various parameters of a distribution, such as the fraction of dynamically recrystallized grains, fabric shape, mode position, or texture strength, stabilize at different length-scales within a sample? In this study, we investigate these questions by creating very large (>500 mm^2) high-resolution maps from individual samples of deformed quartzite and dunite. These large datasets are analyzed by subsampling at different length-scales to allow a quantitative investigation into the spatial variability of crystallographic fabrics. Our results show that large areas must often be analyzed to generate representative bulk fabrics in naturally deformed rocks.