CHEMOD: an automated chemical and modal analysis technique

A digital image-processing technique was modified to provide a more accurate modal analysis of sediments than the standard point-counting procedure. A digital backscattered-electron image covering an area that includes at least 300 grains is processed to form a binary image template for beam control. The automated process re-examines each feature or grain and collects an X-ray spectrum with an energy-dispersive spectrometer. The advantage of this procedure is that instead of analyzing a single spot on a grain, our system rasters the electron beam over the entire grain surface. The stored analyses are background corrected, and the element intensities are utilized to calculate oxide weight percentages for mineral identification. To demonstrate the utility of the analytical technique, six grain mounts of sand- and silt-sized particles from the Cubits Gap crevasse-splay, Mississippi Delta, were analyzed. The technique-referred to as CHEMOD-provides more reliable estimates of feldspar abundances than optical methods because it is based on chemical composition. -from Authors