Preparation condition of rock thin section for electron backscatter diffraction analysis:

Abstract

Crystallographic orientations of minerals were determined by electron backscatter diffraction (EBSD) under a scanning electron microscope. In this study, we introduce a technique for vibratory polishing of rock samples using colloidal silica (CS), for EBSD analysis of quartz in granite and calcite in limestone. Evaluation of the surface state consisted of a band contrast (BC) measure to represent the surface state, a hit rate to represent the success rate of indexing, and a mean angular deviation (MAD) to represent the accuracy of indexing. The factor that most affected the BC and the hit rate was the total amount of displacement of the sample. However, the BC and hit rate also showed a dependency on the crystallographic orientation. When eight Kikuchi bands were detected, the value of the MAD was < 1°, and the MAD was independent of the BC. The BC measure showed that the optimal CS polishing times for quartz and calcite were 3 hours and 1 hour, respectively. When preparing a sample with for the first time, CS polishing for 3 hours and detection of the eight Kikuchi bands provide the most effective method for determining crystallographic orientations.