Microstructural imaging techniques: a comparison between light and scanning electron microscopy

Both light microscopy and scanning electron microscopy are commonly used in microstructural studies of geological specimens. This contribution uses polished thin sections to analyse the same areas in two specimens using both microscopy techniques. The images from a quartz mylonite and a granodiorite are compared to quantitative crystallographic data obtained using electron backscatter diffraction (EBSD). The results indicate that light microscopy images pick out all high angle (>10 degrees misorientation) boundaries but only some low angle and twin boundaries, therefore making it suitable for imaging more general microstructural trends. Orientation contrast imaging, using forescatter detectors in the SEM, images all types of crystallographic boundary: this can obscure the general microstructural trend but makes it more suitable for detailed microstructural analyses. Future studies are advised, wherever possible, to utilise the imaging advantages from a combination of both techniques. (C) 1999 Elsevier Science B.V. All rights reserved.