Aj. Gratz et al., DISTINGUISHING SHOCKED FROM TECTONICALLY DEFORMED QUARTZ BY THE USE OF THE SEM AND CHEMICAL ETCHING, Earth and planetary science letters, 142(3-4), 1996, pp. 513-521
Multiple sets of crystallographically-oriented planar deformation feat
ures (PDFs) are generated by high-strain-rate shock waves at pressures
of > 12 GPa in naturally shocked quartz samples. On surfaces, PDFs ap
pear as narrow (50-500 nm) lamellae filled with amorphosed quartz (dia
plectic glass) which can be etched with hydrofluoric acid or with hydr
othermal alkaline solutions. In contrast, slow-strain-rate tectonic de
formation pressure produces wider, semi-linear and widely spaced array
s of dislocation loops that are not glass filled. Etching samples with
HF before examination in a scanning electron microscope (SEM) allows
for unambiguous visual distinction between glass-filled PDFs and glass
-free tectonic deformation arrays in quartz. This etching also reveals
the internal 'pillaring' often characteristic of shock-induced PDFs.
This technique is useful for easily distinguishing between shock and t
ectonic deformation in quartz, but does not replace optical techniques
for characterizing the shock features.