MICROSTRUCTURE OF SELECTED METAMORPHIC ROCK TYPES - APPLICATION OF PETROGRAPHIC IMAGE ANALYSIS

摘要

Microscopic techniques, such as polarising microscopy and scanning electron microscopy with energy dispersive spectrometer (SEM/EDS), were used in combination with petrographic image analysis with the aim of a quantitative determination of the mineral composition, rock microstructure, and degree of metamorphism of selected quartz-rich metamorphic rock types. Sampled orthogneiss rock types are mainly composed of feldspar, quartz, biotite, and amphibole. The grains are less isometric, elongated, having smooth boundaries, and showing a weak preferential orientation. The deformation and recrystallization characteristics of quartz indicate high-temperature recrystallization (the grain boundary migration recrystallization mechanism). Schist and phyllite rock types are preferentially very-fine to fine-grained, showing a strong shape preferred orientation. Their sedimentary origin was indicated by the presence of graphite. The deformation and recrystallization characteristics of the quartz indicate low temperature conditions of their metamorphism.