ES2 Metamorphic Rocks - Metamorphic Microstructures #17
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Pseudomorph of biotite after garnet.
The brown patch at the centre of the field of view has the regular
outline of a garnet. It consists of a more-or-less random aggregate
of biotite flakes. Elsewhere in the thin section relics of garnet
remain in these aggregates, which are said to pseudomorph the original
mineral. This is the result of polymetamorphism - a thermal overprint
on a regionally-metamorphosed rock.
Field of view is 2.5 mm across.
Polymetamorphic mica-schist, Eastern Alps, Sample DW-0222.
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