Abstract: The microstructure and section characteristics of three kinds of Wudang group schist with obvious foliation were studied by polarizing microscope and scanning electron microscope. Multiple indicators including area percentage, size and perimeter area fractal dimension and directional distribution coefficient were proposed to quantitatively analyze the content, morphology and distribution characteristics of mineral system and pore (micro fissure) system by professional image processing software. The roughness of fracture surface was quantitatively evaluated based on the digital image processing technology of MATLAB. Polarizing microscope shows that the schist has typical characteristics of mineral orientated alignment and intergranular distribution of granular and lamellar minerals. The microscopic quantitative analysis of the mineral system shows that the content of the muscovite of Wudang group schist is 11%~30%. The perimeter-area fractal dimension of muscovite calculated by island method is 1.31~1.39. The directional distribution coefficient is 0.61 to 0.85. Since micro fissure is attached to the edge of muscovite, there is a strong correlation between microscopic indicators of micro fissure and those of mineral. The section of the schist along foliation mainly presents the characteristics of intergranular failure, so the fracture surface is relatively flat. The box dimension of the grayscale signal wave curve based on the profile map is 1.48~1.60. In contrast, the fractured schist section is mainly transgranular failure, with the signs of alternate transgranular and intergranular failure, which lead to rough fracture surface. The box dimension of the signal wave curve is 1.65 to 1.69. The roughness anisotropy of the fractured schist section is about 1.03 to 1.14.

Key words: schist, microstructure, section morphology, image processing, anisotropy