Page 145 - Microtectonics

134 5 · Shear Zones

Fig. 5.22. Quartzite mylonite with δ-type (centre) and small σ-type mantled porphyroclast of K-feldspar. All porphyroclasts show stair-
stepping. A weak oblique foliation trends from top right to bottom left. Section parallel to the aggregate lineation and normal to the
foliation. Dextral shear sense. St. Barthélemy Massif, Pyrenees, France. Width of view 6 mm. PPL

Fig. 5.23. Granite mylonite with a σ-type mantled porphyroclast of K-feldspar (centre) in a matrix of recrystallised quartz. Feldspar
porphyroclasts at the top and bottom are mantled by fine-grained dynamically recrystallised feldspar. The grain aggregate of quartz
probably formed by dynamic recrystallisation but shows effects of static recrystallisation. Section parallel to the aggregate lineation and
normal to the foliation. Dextral shear sense. St. Barthélemy Massif, Pyrenees, France. Width of view 4 mm. CPL