TOWARDS A NEXT GENERATION, OPEN-SOURCE TEXTURE TOOLKIT

Textural analyses are utilized across many geological disciplines ranging from igneous-metamorphic petrology to geobiology. The information encoded in textures are an inroad to characterizing the physical properties of geomaterials and can reveal the processes associated with formation of the constituent minerals. Over the past few decades, there have been significant improvements - both on the instrumental side as well as data analysis methods - in characterizing the rock micro texture and rapid processing of large datasets. However, some serious issues still remain in this field. Because many textural investigations are performed on a thin-section, a critical step before data interpretation is converting 2D measurements to 3D estimates using stereological correction techniques. Existing tools for these corrections are based on a number of simplifying, but hidden, assumptions which may not be appropriate for each dataset. For example, the methods frequently assume that crystal shape is constant across all sized crystals. In addition, these prepacked tools are typically not open source, thus making it hard for users to make modifications as needed for their geologic context. Our study seeks to address these challenges by developing a new open source, transparent, extensible, and statistically robust texture toolkit. For this presentation, we will present a part of our results focused on using Electron backscatter diffraction (EBSD) which provides 2D crystal outlines and crystal orientation—effectively a 2.5D dataset. Using synthetic cut sections, we demonstrate the presence of a previously ignored 2D cut-effect in EBSD data that can lead to appearance of a crystal fabric (in 2D) even for uniformly oriented samples. We have developed an inversion method to correct for this effect incorporating uncertainties due to finite crystal number size (assuming fixed crystal shape). We will use a new EBSD dataset collected from oriented samples taken in profile across the Tunnel Dike, a Columbia River Flood Basalt feeder dike, to illustrate the utility of our methods for natural samples. These results also highlight the need to address the coupled nature of crystal size, crystal shape, and overall fabric by correcting for them simultaneously, and with robust uncertainties, in contrast to traditional 2D analyses tools.