First transient stage (0<g <2):
The volume proportions of yellow and magenta grains increase at the
expense of the proportions of bright blue and dark blue grains. This
is attributed to subgrain rotation and glide induced vorticity, both
of which rotate the grains´ crystallography into orientations that
are more favourable for intracrystalline gliding. Note the formation of
a stable, oblique grain SPO at angles of about 60° with respect to
the SZB.
Second transient stage (2<g<6):
The increase in areal proportion of yellow grains is attributed
to a combination of subgrain rotation and grain boundary migration recrystallization.
The coalescence of yellow grains leads to the formation of a microfabric
comprising yellow and magenta domains. Along the SZB, few small fractures
appear which grow subparallel to the incremental stretching direction.
Steady state (g>6):
The areal proportion of yellow and magenta grains is strain invariant
on the sample scale. On the grain scale, however, a cyclical behavior of
consumption and growth of individual grains. This behaviour is identical
to that of steady state in the HT-LS experiments.
Analogy:
The
microfabric is very similar to that to natural quartz mylonite deformed under
greenschist facies conditions.