Quartz mylonite fault rocks, Stac of Glencoul

The photomicrographs below illustrate the classic mylonite fault rock evolution in Cambrian Pipe Rock Quartzite via grain size reduction due to dynamic recrystallisation to produce a fine grain size fault rock capable of accommodating very large strains. The photomicrographs are viewed towards NNE and were cut normal to foliation and parallel to lineation (i.e. XZ section).

For further details, see the original micrographs and descriptions in: Law et al. 1986, Trans. Roy. Soc. Edinburgh, 77, 99-125.

law01.jpg (49269 bytes)

1. Weakly deformed quartzite with quartz augen (G) and deformation bands.

law02.jpg (57379 bytes)

2. Moderately deformed quartzite; foliation defined by preferred alignment of flattened detrital quartz grains.

law03.jpg (49915 bytes)

3. Variably flattened relict detrital quartz grains.

law04.jpg (65219 bytes)

4. Highly elongate relict quartz grains defined by domains (SA) of recrystallised quartz grains of similar crystallographic orientation that defines the macroscopic mylonitic foliation.

law05.jpg (66040 bytes)

5. Preferred alignment (SB) of elongate dynamically recrystallised quartz grains that dips more steeply than (to ESE) than the mylonitic foliation (SA), indicating sinistral shear sense.

Return to site map