ES2 Metamorphic Rocks - Metamorphic Microstructures #23
Helicitic porphyroblast (post-kinematic).
The centre of the field of view is occupied by a poikiloblast of relatively high relief chloritoid, the straight crystal face on its upper right edge being fairly obvious. The strongly-crenulated foliation in the rock passes without a break right through the poikiloblast, being defined within it by trails of graphite, quartz and other inclusions. Clearly, chloritoid growth entirely post-dates all deformation in the rock.

Plane-polarised light. Field of view is 2.5 mm across.

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DJW - August 1997