Naturally deformed quartz-rich rocks
Figure caption
undeformed / semibrittle & bulging recrystallization / subgrain rotation recrystallization / grain boundary migration recrystallization
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Chert deformed and recrystallized at greenschist conditions. Grain size depends on purity; coarser grain size regions represent quartz veins.
Chert from Pilbara, Western Australia, deformed at greenschist conditions. Very strong macroscopic foliation and lineation. Grain size coarsening is a function of quartz purity, the quartz veins showing the largest grain size. Recrystallized quartz grains are elongate oblique to the main foliation, in a manner consistent with top-to-the-left sense of shear. Deformation occurs in transition between regime 2 and 3 dislocation creep. (119 A)