Microstructural analysis of quartz crystals in an andalusite-cordierite schist using electron backscatter diffraction

The present study investigates the shape preferred orientation (spo) and crystal preferred orientation (cpo) of quartz crystals using electron backscatter diffraction (ebsd) in andalusite-cordierite schist from the ythan valley, aberdeenshire, in the scottish dalradian block. quartz crystals in the matrix and andalusite pophyroblasts have inequant to slightly equant shapes. quartz crystals show weak spo in the matrix and andalusite pophyroblasts, which are sub-parallel to each other. the weak spo in quartz crystals of the studied sample can be related to (1) grain boundary migration of quartz crystals and (2) non-quartz crystals (e.g. mica) at junction of quartz crystals. also, quartz crystals show random cpo in the matrix and inclusion. the lack of cpo of quartz crystals in the matrix can be explained by (i) absence, or low amounts of strain in the rock that is experienced only low temperature and pressure and (ii) diffusion creep. the random crystallographic orientation of quartz inclusions may confirm non-selective orientations of the matrix quartz crystals by andalusite pophyroblast during growth.