These observations suggest that dauphin twinning should be common in stressed rocks and probably represents an example of piezocrescence or the change in atomic positions due to application of stress. All atomic movements are small, do not break Si-O bonds, and result in only a slight difference in bond angles across the composition surface of the twin. Thus, the effect of applied stress is to cause movement of the translation zone at the twin boundary in such direction as to bring the crystal structure into equilibrium with the new stress system. Furthermore, whilst it has been suggested that dauphin twinning will produce an r fabric maximum parallel to the maximum compression direction, it is also known that the maximum seismic P-wave velocity is parallel to the three r directions. One of these r maxima is likely to indicate the compression direction for faulting and all three result in seismic P-wave anisotropy.
Initial indentation causes dauphin twinning of many grains.
In turn a pervasive and penetrative cold-worked region may overprint this with poor or zero EBSD resolution but high electron reflectance. They may also assist diffusive mass transfer processes by the formation of a subgrain array which represents a several orders of magnitude reduction in apparent grain size and hence diffusion path length. This process is consistent with dislocation enhanced selective dissolution. Indentation causes an intensely deformed region, with high electron reflectance but poor electron diffraction, to develop. Fracturing largely controls any plastic deformation, although the absence of voids also implies some strain accommodation via low temperature plasticity.