AUTOMATED MAPPING OF METEORITE THIN SECTIONS USING IMAGE PROCESSING SOFTWARE

摘要: Introduction: The determination of mineral abundances in thin section is an essential diagnostic tool, for thorough petrographic description and interpretation petrogenesis rocks. Mineral modes have traditionally been acquired using a point counting routine, where microscope used to visually classify each present. Drawbacks this method include the relatively small number points analyzed (~ 10), amount time required physically determine minerals present, difficulty identifying fine-grained minerals. An alternative modal involves integration X-ray element maps (obtained from electron microprobe), visualization software. Elemental x-ray mapping provides very efficient informative determining distribution elements section. These can qualitatively show relationships among within section, detect clustering groups, highlight difficult see visually, provide information on zoned minerals, supply field guide future high precision quantitative analysis Scanning Electron Microscope work. This automated process also allows more objective investigation, permits retention spatial throughout yields 2 3 orders magnitude analyzed. density counts obtained valuable estimating concentrations that are occur minor abundance. Technique: Semi elemental polished sections were produced Cameca SX-50 microprobe. To create maps, focused beam was aimed at position held there predetermined length time. capable acquiring five Wavelength Dispersive Spectroscopy images its spectrometers. Each spectrometer set up specific measures resulting emitted intensity. value then defines relative grayscale point, or pixel, seen map. When 10 analysis, immediately repeated, same Probe conditions vary these depending size map, optimize Most 1024 x pixels, generated with currents 50 100 nA, had step sizes between 9 16 microns, dwell times 11-17ms/pixel. All saved as uncompressed .tiff files, order maintain all pixels. imaging program study named ENVI (Environment Visualizing Images), which digital software package normally terrestrial remote sensing. imported into program, map becomes one layer multi-layer image file (Figure 1). In corresponds “band”. pixel has characteristic profile, corresponding total recorded 2). One advantage processing system it possible correct any drift may sets collecting, before starts.