Quantified Strains and Electron Backscatter Diffraction (EBSD) on Quartz Fabrics In the Seine Metaconglomerates
We collected oriented quartzite clasts and quartz veins from several locations with different strain magnitudes. Thin sections were made from the samples in orientations parallel to lineation and perpendicular to foliation. Microstructural observations indicate that quartzite clasts and quartz veins deformed by dislocation creep with subgrain formation and recrystallization recovery mechanisms. Extensive undulose extinction and some subgrains exist in all samples. Grain size and the degree of undulose extinction within grains decreased with increasing strain in quartzite clasts.
Using a SEM-EBSD system and CHANNEL5 software produced by HKL Technology, an automatic map of the thin section was used to determine the crystallographic orientations of quartz grains. The map was constructed to maximize the area analyzed on the thin section with one measurement taken from each grain.
Preliminary results from the EBSD analyses show increased clustering of quartz c-axes crystallographic preferred orientation (CPO) within quartzite clasts with increasing strain magnitudes. Similarly, in most cases, there was an increase in CPO of quartz c-axes within quartz veins when strain magnitudes increased. These observations when taken with the microstructural observations are consistent with deformation by dislocation creep with recovery primarily by recrystallization.