Strength of dry and wet quartz in the low-temperature plasticity regime:
insights from nanoindentation
Abstract
At low-temperature and high-stress conditions, quartz deformation is
controlled by the kinetics of dislocation glide, often referred to as
low-temperature plasticity (LTP). To investigate the relationship
between intracrystalline H2O content and the yield strength of quartz
during LTP, we have integrated spherical and Berkovich nanoindentation
tests at room temperature on natural quartz grains from a deformed
migmatitic gneiss with electron backscatter diffraction (EBSD) and
secondary-ion mass spectrometry (SIMS) measurements of intracrystalline
H2O content. Dry (<20 wt ppm H2O) and wet (20–100 wt ppm H2O)
crystals exhibit comparable indentation hardness, which is proportional
to quartz yield strength. Thus, quartz yield strength, seems to be
unaffected by the intracrystalline H2O content. Pre-indentation strain
history may have had a major role in generating a high density of
dislocation sources, which controlled the yield stress during LTP.